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SHORT GUIDE FOR TEXTILE SCREEN-PRINTING

By Michel Caza – FESPA past President – ASDPT past Chairman - International consultant

N.B. : The text in black means “neutral”, in blue means “good to adopt”, in red means
“bad, to reject”.

A – THE PREPARATION OF THE DOCUMENTS

You must never forget that quality and success in screen printing is a WHOLE.
Without a good document, you don’t have one chance to succeed !
The only manner to transmit a graphic document, artwork, text or image is to use a digital
file. Never send, as I saw in some case, a simple well or bad printed document on paper !

Bad supplied document

A file must be made using softwares, as universal as possible, and it must be strictly identical
in size and definition to the final printed size, whoever it will be destined to :
send exactly the same file in all the countries where Decathlon is printing.

- It can be, for texts, logos, line images in Adobe Illustrator CS5.1, - vectorised,
with Live Trace.
- Or if containing a photographic image in Adobe Photoshop CS5.1.
Be careful, for Photoshop : always in 305 ppi for a good definition and quality,
size 1/1.
- Very important : don’t forget – if you use normal texts - to join the font YOU
used for your artwork.

Font used to send

The fonts, manufactured by many suppliers in many different countries are based
on inch, cm, point, pica, pixel, etc… all different mathematical bases that are
impossible to make in perfect concordance.
Those files can be translated in PDF, ideally Certified PDF.

B – THE WHOLE PREPRESS IN PRINTING PLANT

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1 – THE TREATMENT OF DATA ON COMPUTERS

Actually, if we speak of textile screen printing of garment - directly or indirectly (transfers) – a

film is made to stencil the screen later in 95% of the cases. So far, I saw only two
companies using the tool of the future for screen printing being “REAL”(not through opaque
ink-jetted ink) CTS, Computer To Screen, where no films are used as the image or design
is directly transferred from the computer to the screen through mostly direct UV light (with or
without laser) to harden the emulsion on the screen according to the desired image.
Of course a RIP (Raster Image Processor) is used for those digital output (actually mostly
with CST, Kiwo Screen Setter and Sign Tronic(;32/'), to convert the image in UV RUEOXHODVHU
light impulsions. This means that you, the printer, must control and read the files received, even if
you ask this to a specialised company – colour separator, film maker, etc. – and be sure that it will
beusable for the best printed result.
Then, you must have the software’s (Illustrator, Photoshop, PDF), using PC or Macintosh
computers.

It is YOUR responsibility to make sure your own film department or your subcontractor
receive the correct data to succeed.

2 – THE FABRICATION OF THE FILMS

Third critical point.

a) “LINE films”

Left high – middle = BAD ink-jetted films - Left down = GOOD imaged file

THE USE OF INK JETTED FILMS MUST BE RESTRICTED, for fine lines or halftones (the
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possible fineness cannot exceed 115/inch… With a good correction of densities !)

The reasons ? : lack of “edge definition”, lack of good opacity.

So far, the best film or films destined to screen-printing remains through the use of “silver
films”, (even the “thermal films” are far to be sufficiently good for high quality).
This means that your company (or your subcontractor) must have an “image setter” (Kron,
Agfa, Dainippon, Katana, etc.) despite this is a relatively big investment.

Image setters

The other “good alternative” is the one I spoke above about – and the near future – the CTS
(Computer To Screen, to see later).

Even here, the quality of the image setter and of the RIP that pilots it is very important : there
must be enough PPI (Pixels Per Inch) provided to insure the perfect quality of the curves,
rounded letters, etc. in a manner to prevent any “scale effect on the edges” as seen above.
A GOOD FILM, AFTER THE GOOD FILE, IS THE SECOND RULE FOR SUCCESS.

b) HALFTONE films

Halftones, 4 col. Process enlarged detail – other “full image 305 ppi
Despite those types of image are actually not too much used, this may change in the future
with the use of more “sophisticated and fashionable” images.
Knowing that too often the definition of those images are very poor, I advice the use of a
minimum of 75 lines/inch (30 lines/cm), as well for direct printing as for transfer printing.
For quality printing, the dots should not be visible as such (dots) on the garments.
New technologies such as UV water based screen printing allow to print up to… 300
lines/inch (120/cm) on garment !! But this is so far an other story…
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The shape of the dot to be use is better “elliptical” rather than square or rounded.
The angles are normally 0° for Yellow, 15° for Cyan blue, 45° for Black and 75° for Magenta.
This can be changed to what we name “flexo angles”, respectively 7,5°, 22,5°, 52,5° and
82,5°.
Question of habit and relation with the fabric of the screen to avoid “moiré” problems.

Moiré problems are often critical in textile printing because in addition to the problems of
relation between the film dot lines and the threads of the fabric on the screen, you have
to face a third possibility of moiré between the image and the threads of the printed
material itself !

The use of “stochastic” halftone diminish this risk of moiré of 90% but is relatively
difficult to master without the knowledge of this relatively complicate technology that I
created 45 years ago !

c) INDEXED colours

Indexed 9 colours image

This technique, popular with the use of multicolour carrousels, permit to reproduce a full
colour image in a bitmap colour separation between 7 to 13 or 14 colours. This needs to
have a very skill full CAD designer…

3 – THE CHOICE OF SCREEN FRAMES

Five main types of frames used in screen printing :

- purely wooden frames : totally obsolete and I prohibit their use.
- Mixed “wood/iron frames : frequently used by the printers using the “long tables”…
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Wooden frame, even joined with iron = NO

Not very good, iron is causing contamination of water based inks by rust
particles.
- Purely iron frames. Heavy and submitted to rust, then contamination of water
based ink, as above.
- Aluminium frames, lighter, better, more resistant to very high tensions if pre-
bended, to compensate the very high tensions above 25/30 Newtons/cm.
ADVICED.

Good storage of frames

- Even better, but I rarely saw them except in USA and European countries, the
self-stretching frames.
- The most famous being the Newman Roller frames from Stretch Device also
sold in Europe and Asia through DUBUIT.
Of course, this is an higher investment for the company, but compared to classical
aluminium frames, the “stretch and glue”, it can be used and re-used many
times without changing the fabric (100 different successive images is a
possibility) and such a screen with a tension of 30 N/cm that it will keep all its life
can support more than 200,000/300,000 prints.
It allows to maintain a constant and identical tension for all its life
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The Newman Roller Frame

4 – THE CHOICE OF SCREEN FABRICS

This point – as the following, the tension of the screen – is MOST IMPORTANT.
One thing is extremely clear, even before choosing the number of threads to use according
to the ink deposit : the colour of the screen fabrics.

a) THE FABRIC MUST BE YELLOW

If you want to print sharp, precise fines lines, edges of design, dots in halftone
printing, you must know that one of the major factor is to prevent the
dispersion of the light in the white threads when exposing the screen is to use
YELLOW fabrics.

The illustration here shows what happen to the light on white and yellow fabrics.

When we replaced silk and Nylon fabrics in screen at the advent of both polyester in
combination with direct emulsion to make the screen - at the end of the sixties - we
discovered the problems engendered by the dispersion of the UV light inside of the threads
and knots when crossing.
We chose the orange colour. This colour had to be turned to yellow when the orange dye
used was recognized as “chemically dangerous for health”.

The operation is a simple dyeing of the meshes and an increase of the price would
NEVER exceed 5% !!

The troubles engendered by a bad screen – fabric + tension – cost quite often much more
that this very slight increase of the fabric’ cost and the fact you have to increase of 15/20 %
the exposure time of the screen in comparison with the white fabrics.
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b) THE FABRICS HAVE TO BE CONSTANT IN QUALITY

The weaving, meshes opening, exact number of threads must be identical from a
delivery to the next.

c) THE FABRIC HAS TO RESIST TO THE “VERY HIGH TENSIONS”

The benefit of very high tensions has been proven and the fabrics must be solid
enough to resist without breaking or exploding.(see chapter 5), if the correct tension
procedure is followed.
The fabrics named LE (Low elongation), HT (High Tension) allow those high
tensions.

The fabrics are weaved TW (one thread crosses two) or much better when possible
PW (Plain Weawe).

For all the above reasons, we strongly advice to choose the yellow fabrics from the
Italian company SAATI.

d) THREAD DIAMETERS
Screen printing is often based on “compromises”.
Of course, the diameter of fabrics threads changes in relation with the number of
thread per cm. It can vary from 200 µ (in a 20 thread /cm) to 31 µ (140/cm) and even
less (27 µ).
- In a screen fabric of 140 threads/cm (355/inch) you can normally choose between S
(fine threads: 27µ), T (medium threads 31µ) and HD (big threads 34µ). –
Each of them have often contradictory advantages and disadvantages.

The compromise is to choose “T”, 31 µ with 140 T, good enough both for high
deposit and excellent fineness of lines or images combined with a good enough
resistance to stretching.

e) THE NUMBER OF THREADS TO CHOOSE

As you know, it is related to the needed ink deposit : in flat tones and large printed
areas, the fabric determinate 70% of the ink deposit.
- the number of threads is between = 43 T to 90 T/cm (110 to 225/inch)
- On white or clear cotton or polyester = 63 T to 120 T/cm (160 to 305/inch)
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- On black or dark fabrics = 43 T to 77 T/cm (110 to 196/inch)

- For halftone printing = 77 T to 120 T/cm (160 to 305/inch)

If an heavy deposit (in thickness) is needed – high density – or if big particles

included in the ink have to be deposited – glitters or other metal particles – it is better
to choose fabric from 15 T to 30 T/cm (32 to 81/inch).

5 – THE TENSIONING MACHINES

To obtain a high and regular tension of the screen fabric, a machine must be used.
Manual tensioning used in the past and still used by a very few companies still
working with wooden frame and staples (!) is totally obsolete and… prohibited.

a) There are on the market several types of tensioning machines, mechanical or

pneumatic from different countries (China, Japan, India, USA, European countries, etc.).
For many reasons the pneumatic machines are better than mechanical ones and in those,
one from Saati (Italy) and from Grafica (India) are the ones we advice to use.

Good tensioning machines, all pneumatic

The fact the tension – with Saati pneumatic tensioning machine - is made without contact
with the frame itself permits to avoid breakings of the fabric that can be engendered by
some irregularities on the metal frame surface or remaining traces of glue from the past
recovered screens.
There are some - mostly mechanical - machines we do not advice to use:

Bad tensioning machine, mostly mechanical

The natural loss of tension.

Unfortunately, this due to the nature of polyester itself, the tension is not stable if we consider
the factor “duration or length in time”.
If the tension of the screen is achieved, let us say at the level of 30 Newtons/cm, the day
after it will naturally fall down to 27 N/cm. After stencilling, washing and drying, 25 N/cm will
remain and after a first use to print let us say 1,000 pieces, manually or mechanically, it will
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fall to 22/23 N/cm. And, after some uses and two weeks at a remaining tension of 20 N/cm, it
will be considered as “stabilised” EXWORZIRUPHfor most of its life.

Once the tension achieved (see below the very high tensions), you need to use a good glue
or adhesive to glue the fabric on the frame. This glue must resist to all the chemicals used to
prepare the screen, to the solvent or water in the inks and when washing as well as the used
emulsifiers to reclaim the screen.
We advise to use glues either two components Ultrafix SB1 Plus or the Utrafix CA150
activated with spray (Saatichem).

b) An other good option is to use “self-stretching frames”.

I name those frames “dynamic frames” by comparison with the classical “passive” ones,
the normal “stretch and glue” frames.
We don’t want to make of the use of these frames an obligation.

- Their main advantage is that they allow to maintain at any time, even months
later, the wished initial tension such as 30 N/cm or more of course. The “natural
loss” is compensated in seconds.
- Other advantage, the fact you can immediately adjust the tension to compensate
a problem of register between one colour and the following due to a move
(extension or retraction) of the printed substrate.

Recommended, the Newman Roller Frames (US) sold by Stretch Devices and Encres
Dubuit all over the world.

Newman Rollers Frames and Roller Master for “automatic stretching”

They can be stretched (and re-stretched) in a quite automatic and simple manner using the
Newman Roller Master fully adapted to a speedy tension of those frames.
Other advantage, of course those frames don’t need any gluing, and this avoids the use of
some of those cyano-acrylate or two component glues.

6 - “THE VERY HIGH TENSIONS OF THE SCREENS”

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“Very high tensions of screens” means tensions between 30 and 100 “Newtons/cm”.

This knowing that for most screen printers the tension of their screens they work with is
situated between 10 and 20 Newtons/cm - a fact to which they accommodate without being
really satisfied since it is actually the cause of numerous technical problems they will
constantly have to face... too often without even knowing it!

A poor tension (even extremely poor tension – less than 10 N/cm) is one of the most
universal cause of troubles in the textile printing companies.

Understanding the role of the screen, then realizing what the very high tensions of
this screen can bring to the improvement of the quality and productivity is more and
more essential for the screen printer.

a) THE ADVANTAGES OF PRINTING IN “HIGH TENSIONS”

- a lighter distortion of the image,

- a higher printing speed,
- a much better quality of image, halftone or fine line,
- a much more precise register,
- more constancy therefore less adjustments, from the beginning
to the end of the printing process,
- a much lesser wear of the squeegee blade,
- a lower consumption of ink,
- a much better control of the quality of the printed image
- a faster move from one colour to the next,
- a much superior repetitiveness of one printing to its posterior reprint,
- therefore and finally, a strongly increased productivity.

b) THE FRAMES ADAPTED TO HIGH TENSIONS

Because of their physical and chemical conception, their weaving and treatment, we
therefore have fabrics designed to bear or rather “allow” these much higher tensions (of
which I have listed the advantages).
A “finalized” screen, before stencilling, is of course a fabric but also a frame.
Fabric and frame are apparently two static elements when compared with the dynamic
elements that are stretching and printing.
In fact, just like the fabric and the changes in its behaviour (the ones we have mentioned),
the frame, although called “passive”, is not an element as static as it seems. The pressures
generated by the tension of the fabric on the frame modify and determine its parameters of
behaviour, therefore manufacturing.
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Furthermore, there are some types of active frames, the ones mentioned above, the “self-
stretching frames” of which “actions” can be determined or modified by their user himself,
directly on the frame and not through a tensioning machine.
Taking a maximum advantage of the possibilities offered by the very high tensions and the
fabrics that allow them, forces to take into account the behaviour of the frames facing these
new constraints.
Then, advice your manufacturers of frames to supply you with aluminium frames able to
resist to tensions of 30 Newtons/cm or more.

c) HOW TO STRETCH THE FABRIC WHEN USING “VERY HIGH TENSIONS”

Let us note that this absolutely necessary procedure plays in favour of the over-sizing
of the screen, if the press allows it, according to the size of the printed image. The
farther the printing is performed from the edges of the frame and especially the corners,
the more reduced the risks of distortion of the image in general and the local moiré in
halftone printing in particular, will be.

It is now time to proceed to the stretching.

In order to precise and explain, I am listing below the data that are used for the stretching -
as a “reference” - a polyester fabric from 20 (50/inch) threads/cm to 120 threads/cm
(300/inch), T, TW, PW if possible with a diameter of threads of 34 microns - then on the
right, the data applied for a polyester fabric exactly equivalent in diameter and number of
threads but LE/HT, PW (low elongation/high tension, woven “all gauze”: PW) :

- First stretching: TW = 18 Newtons/cm

LE/HT PW = 23 Newtons/cm
Pause for the fabric for 15 (minimum) to 45 minutes (maximum) :
Residual tension: TW = 15 Newtons/cm
LE/HT PW = 19 Newtons/cm

- Second stretching: TW = 24 Newtons/cm

LE/HT PW = 29 Newtons/cm
Pause for the fabric for 15 (minimum) to 45 minutes (maximum) :
Residual tension: TW = 20 Newtons/cm
LE/HT PW = 24 Newtons/cm

- Third stretching: TW = 28 Newtons/cm

LE/HT PW = 34 Newtons/cm
Pause for the fabric for one night (10 to 15 hours) - if possible :
Residual tension: TW = 24 Newtons/cm
LE/HT PW = 30 Newtons/cm

- Finally, fourth stretching : TW = 32 Newtons/cm

LE/HT PW = 42 Newtons/cm
After a pause of one hour, we glue the screen if it is the type “stretched-glued”.
A self-stretching screen will also have to rest for 45 minutes to one hour.

In any cases, it is better to allow these “very fresh” screens a 24 hours stabilization before
stencilling.
After stencilling, the residual tension will be:
TW = 27 Newtons/cm
LE/PH PW = 36 Newtons/cm

(remark: after the pause, degreasing, coating, exposure, washing and drying of the screen,
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the drop of tension reaches 4 Newtons/cm in the case of “normal” TW and 5 Newtons/cm in
the case of LE/TH PW).

After a first run of 500 to 1,000 copies, the values of tension will drag to :
TW = 22 Newtons/cm
LE/HT PW = 32 Newtons/cm

In time, that is to say after several re-utilizations of the screen for stencilling and printing,
and about fifteen days, it is appropriate to consider that the polyester will have reached its
quasi-final stabilization point to which it will remain almost all its life :
TW = 20 – 22 Newtons/cm
LE/HT PW = 29/30 Newtons/cm

ON THE OTHER HAND : the self-stretching frames allow the “fifth step”,
that is to say after the first run and the next as well, bring the tension back to a level
considered optimal for printing:
TW = 24 Newtons/cm
LE/HT PW = 34 Newtons/cm

Remark : only the “slow procedure” described above will allow the user to obtain screens
stabilized to the required tension, without risks of “explosion” BUT only the self-
stretching frames allow to keep it during the entire life of the screen.
Finally, it is easy to see right away that the polyesters LE/HT PW allow to reach and
- especially with the self-stretching frames – to keep a tension superior by 10 Newtons/cm
to the tension obtained with traditional fabrics.

NB : For the screens between 15/cm (37/inch) and 63/cm (157/inch), it is possible to
start at the second step (24- 29 N/cm), saving then one step in tensioning time.

But don’t try to reach those tensions in only one or two steps : your screen will literally
“explode” either immediately or, after gluing and during the following 12 hours.

7 – THE CONTROL OF TENSION AND THE CONTROL TOOLS

The controls must be done as the following illustration shows it :

Control on 5 points – 2 options Electronic Tension Meter Sefar

For the tension, the tools for control are the “tension meters”.
They are either mechanical, several brands, such as Saatiprint, Grafica, Tetko, Sefar, and
others, or, electronic, the most famous being the one of Sefar, Switzerland.
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Normally, the electronic ones are more accurate and precise. The mechanical, cheaper, are
based on the tension of a spring and it need to be re-calibrated quite often, especially in
the climatic areas where humidity are often above 75% and the temperature often above
25°C.

Tension meters from Sefar (electronic) - Grafica and Saati (mechanical)

The printers must of course buy one - and choose the one they like to invest in - but they
must take care of the necessity, if those tension meters are mechanical, to ask their supplier
to check each six month if the calibration of the spring is correct, according to the local
weather conditions.
The electronic models such as the one of Sefar are safer and can be re-calibrated by the
user.

8 – THE TECHNIQUES OF STENCILLING

Another point of a huge importance if we speak in terms of quality, sharpness and

resolution, edge definition and of course quality of reproduction of image in halftone process
colour or indexed colours.
In textile screen printing, the most used technology is the one named “direct stencilling” :
95% of the screens.
Capillary films, devoted mostly to high density and other special applications represent 5% of
the stenciOlLQJ.

To make a stencil needs certain equipment specifically adapted to the stencilling of the
screen.

The quality of the stencilled screen is also one of the most important point, joined to
the quality of the file, of the film, of the tension of the screen and the colour of its
fabric.
Once again I like to recall that a high quality printed result is the combination of those
several elements.

We saw above how to make and stretch the “basic” screen: a fabric stretched on a frame.
Now, we will see how to transform it in a tool able to transmit an image or a design on a
substrate through “direct stencilling”.

Step 1 : preparation of the screen fabric when new stretched.

Step 2 : Choosing the emulsion
Step 3 : Coating of the screen with the emulsion
Step 4 : Drying of the emulsion 1 or/and 2 times.
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Step 5 : Exposure of the screen trough the film made (or, rarely actually in CTS)
Step 6 : Developing the screen through washing it with water
Step 7 : Drying
Step 8 : Control and retouch

Those different steps needs more or less sophisticated equipments.

We consider that some of them are an obligation and some others are “facultative”.

a) Preparing the fabric of the screen

Most of time, the first time a new stretched frame is tensioned, it is recommended
To prepare the fabric to allow a better adhesion of the emulsion and a greater solidity
of the screen while printing.
Remember : when you wait a screen, the water must remain inside of the fabric :
as a full, continuous and complete film of water and not to “refuse” this water per
places. This remains the best test to judge the “wetting capacity of the fabric, then a
good adhesion of the emulsion or the film.

As the choice of fabrics advised are the yellow ones from Saati, you can use
Saatichem DIRECT PREP 1 which is a ready to use one step mesh abrader, wetting
agent and degreaser (simply follow their instructions for use.

b) Choosing the emulsion

There are mainly two types of emulsions : the pure polymer and the diazo-polymer.
Both can be used, but I am in favour of the second one, the diazo-polymer, for the
simple reason that the suppleness in length of exposure is much higher from 1 to
10 or more instead of from 1 to 2 maximum.
The second important point is to have an emulsion containing enough of solid
particles, both because the use of screen fabric often very “open” and because of a
better “edge definition”. It must be a minimum of 45% and better around 50%.
As we decided to advice the products from Saati Chem, the best emulsions are :
Textil HHU a diazo photopolymer (45% solid) – Textil HT Fast (47% solid) – Textil
HT both diazo photopolymer (48%) – Textil HHT a diazo photopolymer triple cure
also used for special effects (50% solid).

Some of those emulsions, when used with water based inks need an extra
exposure (“post exposure”) after developing for better resistance.

For special effect such as high density, the best emulsion is Textil PHW a pure
photopolymer (50% solid). To use with a multi-coating. Accurate exposure needed.

c) Coating the screen

This operation remains is most often a “manual” one, at least in most of the textile
printing companies with a metallic “hollow squeegee” or “scoop coater” or
“coating trunks”, but, of course there are machines, more or less automatic to do it
and that is what would be preferable to insure a certain consistency in quality.

See pictures:
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Coating trunks manual coating

Through the whole range of coating machines from Europe, Usa or Asia, we strongly
advice to choose the ones from Grafica Flextronica (India), a company which offer
excellent equipments ranging from “semi manual coating machine to fully automatic
one for one side or double side coating, with a good relation between price/quality.

semi-auto coating automatic coaters (Grafica)

For most normal applications, I recommend 2 coats on substrate side of the

screen, plus 1 coat on the squeegee side.
For an even higher definition, add 1 coat on the substrate side, after drying of
the initial coat.

If you need a very thick screen – for high density - with a coarse fabric (24 to
32/cm), and prefer to work with direct emulsion (here TEXTIL PHW, a pure
photopolymer) instead of using thick capillary films, you will have to add several
coats of emulsion = from 6 to 8 additional coats (immediately after the 2 initial
substrate side) on the squeegee side. You will get a total emulsion coat around 350
microns. But I prefer and advice to use capillary films for those high density prints.

d) Drying the emulsion

The best manner is to use a drying cabinet (dark of course) with racks made in a
manner the screen can dry in a flat position, substrate side down to have the best
possible EOM (Emulsion Over Mesh) and possibly a low Rz value (smallest
possible difference between the highest and the lowest thickness of emulsion).

The drying temperature, if some is used in the cabinet must never be above
38/40°C.
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Drying cabinets for screens before exposing and after developing (Grafica)

Last important point : once the emulsion dry, both before exposure and after
developing of the screen, the percentage of humidity contained in the emulsion
must never been above 4% if you want to have a solid and resistant screen.
This means that you need a tool to measure it, if possible.
Advised: TOM AQUA-CHECK from Saatiprint.

e) Exposing the screen

Another step of huge importance !

Computer To Screen from CST (Germany)

Total investment or additional ones, for example the installation of a light integrator
to control with a total precision the amount of light received by the screen.
The systems of exposure are globally of two kind if we consider the source of light :
- UV fluorescent tubes, or
- Metal halide UV lamps.

The tubes ?
Forget about it !
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UV tubes – obsolete and un-sharp – poor or even non existant depression
- to be used only for re-enforcements of emulsion.

The metal halide lamps are of course the one to use.

But here again you have different types of “exposing units” – an exposing unit being
composed of a vacuum frame with a supple carpet, a pump to create a strong
depression and then a perfect contact between the film and the coated screen, a
metal halide lamp and, for the best models, a “light electronic integrator”.

The lamp can be placed under, above or laterally. Power = 1, 2, 3 to 5 KW.

The distance between the lamp and the vacuum frame must be, at the absolute
minimum, the length of the diagonal of the biggest stencilled frame (or of the
addition of several smaller frames if they are exposed together).

Vertical lamp above, horizontal and semi-horizontal (Grafica) – no heating of

glass

Many of the models I saw in textile printing plants had the lamp under, and often not
at a sufficient distance to obtain a proper coverage of the screen(s) by the light.

All models with the lamp UNDER = overheating of the glass (then screen)!
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This cause a problem related to the fact this lamp which can either be hidden behind
a shutter when not used (then still warming), or being “re-lighted” through infrared
additional systems, engenders an heating of the glass of the vacuum frame. A UV
lamp emit wave-lenght between 250 and 5,000 NanometHU that is to say not only UV
but also visible light and many infra-red (= heating as you know!).
This presence of heat causes an overexposing of the emulsion which can be very
damageable when halftone dots or fine lines have to be stencilled, and a
parameter that even the light integrator cannot take into account.

Contact in vacuum frame: very important because to have a perfect reproduction of

the film on the screen, the contact between screen and film must be absolutely
perfect.
The quality of the lamp and its degree of tear is also extremely important, the
amount of UV light sent for exposure reduces in time and the life of the lamp is
warranted by the manufacturers for a maximum of 1,000 hours at full power.

Damaged lamp Awfull contact in vacuum Perfect contact

The lamp must be cleaned each 2 weeks, with isopropyl alcohol. Don’t touch the
quartz with naked fingers to not damage it. Use cotton gloves.

The exposure : another vital point is the one of the duration of exposure.
The manufacturer of the emulsion often give data about the exposure….
BUT too often in term of “time or duration” !

You need to know that the exposure time - which can be critical when it is question of
halftone printing, indexed colour or very fine lines – when based of the time of
exposure give an output of UV light totally depending upon the constancy of
the electricity supply !
And the major problem is that the electricity supplied to your plant by the State, City,
Private or Public company, is far from being constant.
According to the general consummation in the city, different in the morning, or lunch
time, or afternoon, you receive a stream with a lot of variations, both in term of
voltage and intensity.

To be quite clear, this means that at certain moment – for the same duration of
exposure – your screen will be correct (maybe) or underexposed, or
overexposed !!

What is important for the screen is the “exact amount of UV light it receives”.

To solve the problem, there is a tool named “electronic light integrator”, where a
cell on the glass of the vacuum exposing unit, measures exactly the amount of light
received, and a simple software integrated in a coupled computer permit to cut the
light automatically when the exact amount of light is reached.
19    

You have to programme, to set a certain amount of light – lumens for expl. –
generated in “impulsions of light”, that is the best for your screen for a certain
definition and quality.
You will have to establish it by experience - using the photographic test films supplied
by many manufacturers – the correct number of light impulsions for the best
result.

This will permit your screen to receive EXACTLY the amount of light needed with
absolutely no dependence from the intensity of the supplied electricity.
In addition, the integrator will inform you when it is time to change the lamp.
The lamp need to be cleaned each month with isopropyl alcohol. Take care not to
touch the lamp with naked fingers (trace of sweat will damage the quartz), use cotton
gloves.
Grafica (India) supplies an excellent exposing unit with light integrator.
A German company named BELTRON supply this kind of equipment which can be
adapted to most models of exposing unit equipped with a metal halide lamp between
1,000 and 7,000 Watts. (1 to 7 KW).

f) Developing the screen

This operation remains in most cases manual, using normal water pressure and
sometime a high pressure water gun with pressure reduced to 30/40 bars.
There are automatic developing machines, often in use when included in a fully
automatic screen making unit as it exists a few in the world.

Developing the screen after exposure

This development must simply be perfect and don’t leave any poorly washed area in
the image on the screen.

g) Drying after developing

This must be done carefully after wiping excess of water remaining in the screen to
prevent traces in the open area of the screen.
In this last case, it is better to leave the screen to dry vertically.
A slight heating can be used, but again never more than 40°C.

Sometimes, as mentioned above in “exposure”, a second exposure after developing

and drying is necessary, to have a more solid screen when using some water based
inks.
And, if possible, to control the moisture inside of the emulsion on the screen :
remember, never above 4%.
To measure the internal moisture in emulsion, you can use TOM AQUA-CHECK
from SaatiPrint.
20    

h) Retouch and control

One of advantages of CTS is that in general there are no “pinholes” to touch, as they
are often due to dust on the film or on the glass of the vacuum stencilling unit.
Using the classical technique with films, each screen must be checked on a lighting
table (with a combination of bulb lamp and tubes) : the light given by the tubes
being not so punctual, some pinholes remains visible only through a more punctual
source of light such as the one given by the bulb lamps (no need to be above 45
watts).

Retouching the pin-holes on the screen

For the retouching and finishing product, you can use FINISH W1 from SaatiChem.
It is fully resistant to water based inks and can be reclaimed with the stencil remover
products.

9 - THE CAPILLARY FILMS AND THICK FILMS

The “multi-coating of emulsion” to produce stencils for high densities is far from being the
best and is not a simple one !
Use thick capillary films that can be mounted under the screen simply with water, or, for
more resistance, with an emulsion such as Thik baking Emulsion (SaaticChem). We
name it “direct-indirect”.
In addition to the thickness, one of the big advantages of those films is to “cut the meshes
opening” in the screen fabric, even if very coarse (such as 15 or 20/cm (37 or 50/inch) and
provide then an excellent edge definition and sharp images.

Those films are produced by several companies (Murakami, Ulano, Autotype, Kiwo, Sericol,
etc.) but I advice to use, to be “coherent”, the one of SaatiChem :
the THIK FILM.
Presensitized, It exist in thickness of 100 to 400 microns and in size of sheets of 22 x 36
cm and 36 x 43 cm. High resolution and easy to handle.

10 – CONSERVATION AND RE-USE OF SCREENS AFTER RECLAIMING

Many companies, use to keep the stencilled frames (screens) for a certain time – 3 to 6
months – in case of re-edition or completion of orders given by the customer given later,
during the “season” mostly.

Most of those companies, instead of reclaiming ink and emulsion and reusing the screen
destroys the fabric and replace it by a new one. This is costly, meaning less, takes a lot
21    

of time by immobilising the tensioning machines, and if you add to this, the cost of the fabric
itself.
A yellow screen with a high tension (more than 25 N/cm), stretch and glue or self
stretched, can be reclaimed and re-used with new image at least between 50 to even
100 times and can support 200,000 prints or more…

Our recommendation : if the screen is stretched as seen above in very high tensions,
keep it, reclaim it carefully and re-use it !

Reclaiming the screen Finishing reclaiming

To reclaim the screens you need a high pressure water gun – 120 bars – and some
products here again supplied by SaatiChem
They must be able to remove the rests of ink,( screen wash/ink degradents), to remove
the stencil (emulsion or capillary film and retouching product) and to remove the haze (also
named “ghost images”).

Those products, as less aggressive and most “green” as possible are :

Stencil remover : REMOVE ER1 or ER4
Haze remover : HR3 or HR4 (the cleanest, no caustic, no corrosive chemicals).

Careful storage of the screens to be kept for future re-editions

C - PRINTING ON THE PRESS

We are now supposed to have an excellent screen, made according to the best state of the
art rules.
The printing process itself, manual or automatic, must also be done according to good rules if
we want the print be perfect in quality, repetitiveness and at the same time respond to the
22    

criteria required in term of protection of health and environment both for the
manufacturers, printers as for the end users – the final customers.
The second rule being at the same time the protection of the local environment and, as
soon as possible, the reduction of the carbon footstep.

As logical, at this stage, the main concern is about the inks.

It exists, for the main customers very precise leaflets, such as the Chemical Substances
Management.
The chemical products considered as dangerous in this book must definitely be banned from
any product destined to one Brand.
A non respect, for example with the use of phtalates in plastisol inks can cause the reject
of the totality of the ordered quantity at the first step, and a definitive suppression of
the orders to the company making this kind of “big fault”, even by simple mistake !

1 - CHOOSING THE INKS

Ink and colour lab.

To both be sure of the quality of the products, of the similarity of print from one country to the
other I advice to choose on one hand, the inks from the Indian Company ZYDEX
(info@zydexonline.com and www.zydexindustries.com ).
They are able to send their products as well in Asia (China, Thailand), Europe, Turkey,
Romania, $PHULFDVNorth Africa (Morocco, Tunisia) and Central Africa (Mauritius, Madagascar)
and, of course, India !.
On the other hand, if you keep conscious of the necessity to use water based inks, you can
also work with some of the other Major companies in the world such as Rutland, Willflex
(Oasis), KIAN (Aquaprint), KFG

The reason I chose Zydex on the first hand, is related both to the quality of their water
based inks and products, their possibility to deliver in the countriesZKHUHELJRUGHUV IURP
WKHZRUOGRIVSRUW and to the fact they have a huge experience of the “green products” since
more than 1 years, with a fair relation between price and quality.
23    

We also do not advice to use the quality of mixer, the quality of pigments bought at some
suppliers that can even contains “heavy metal” , VOC and also because of the too irregular
and no repetitive results that they cause too often !.

a) Water based inks

The actual tendency on the market – following the rules about health and environment and
the “cautious principle” - is to use more and more water based inks to replace the
plastisols, even if those last inks does not contains phtalates and PVC.

But, following what I saw in several countries, I do not advice to make your own mixing of
colours, using pigments and transparent base bought separately with too often uncontrollable
results such as poor quality in adhesion, opacity and stretching ability, plus other problems
related to the specific rheology of the ink, the eventual content of heavy metals in pigments,
the drying in the meshes of the screen fabric, lack of resolution and definition !
Don’t use “home made inks”!

A SAFE result, even with an even slightly more expensive ink will save a lot of money
because of reducing the rejects, due to poor print quality, and even the risk to loose the
customer as well as permitting huge gains in productivity when combined with the other
factors “from the screen to the print”, we already saw here above in prepress !.

The plastisols can still be used – as less as possible and only when their replacement by
water based inks is impossible - if they do contain neither phtalates (the most important),
and often nor PVC (this fact being for me more unclear because PVC has never been
proven dangerous for health, since more than 30 years it exists and is used in construction
and in so many applications !).
Remember, most phtalates have been proven carcinogenic, mutagenic, repro-toxic !
and classified R.48, R.60, 61 and 62 according to the European regulations.

It is quite clear that the water based inks are technically more difficult to print than plastisols
(problem of drying in the screen fabric), and that the plastisol without phtalates and PVC are
more expensive and more difficult to print !
But, the “Principle of Cautiousness” applied by most of the major sportswear manufacturers
in the world (Europe, USA, Japan…) is very strict and even more when it is question of “baby
clothes” (or children under 5 years).

The installation of the REACH rules in Europe – now official (Registration, Evaluation,
Authorization of CHemical) will re-enforce this tendency and definitely prohibit several
chemicals from importation, alone or mixed, or included in manufactured products (then also
garments).
That is why it is so important to take care of the recommendations of the Major
Customers in term of choice of inks.

Important to remember also that this restrictions concern as well the “direct screen
printing” as well as ink used for screen or digital printing of “transfers” (which can be
consider as an “indirect application” of the same printing technology).

Remember also that a contamination of water based ink by the plastisols can be made by
simple proximity = use two different rooms for ink storage and ink mixing.
This concern also as well the screens, the tools, the squeegees, the containers, etc.

The best would be even a complete separation inside of the plant between parts
where plastisol are printed (especially if they still contain phtalates) and the printing
of water based inks. Some companies do it already.
24    

Now, which ink for which application ?

The water based eco-friendly inks proposed by Zydex are the following:
K2, spot colours
K4 trichromatic and hexachromatic colours, CMYKGO
K2 opaque
K2W for Denim, polyamides, polyesters, elasthanes and high densities.

The manufacturer indicate which fabric to use with which inks. The very opaque inks
supplied (K2 opaque) allows to print on dark substrates avoiding the “multiple squeegee
stroke” - I am absolutely against it : loss of time, poor productivity, lack of sharpness - :
the very high tension permit to avoid these multiple strokes.

It exists – for example - 3 whites : K2 Base White, K2 Top White and K2 Mixing White
more or less opaque and offering a high stretch ability (extension ability) when K2 Clear
added between 20% to 40%.
In general, the adhesion is from “medium to excellent”, the stretch “high or medium”
and the peeling resistance “medium or high” (with fixer).

The viscosity can be changed using Zase 5100 as a thickener and K2 Ink Reducer to
reduce the viscosity.

The feel of those inks is smooth and soft, and, if needed, a softener (R55) can be added to
make the ink surface even smoother.
If a more matt effect is desired 5 to 15% of K2 Matt can be added.

Last point, the pot life (or shelf life) is of a minimum of 18 to 24 months, when the lid is
tightly lid.

b) Discharge inks
For discharge prints, check is the proposed material has been dyed with the special dyes
made for discharge. Even if I don’t, some peoples like discharge technology because it keeps
the fabric a softer touch.

The other face of the problem and my own concern relay on the discharge inks for screen
printing themselves. They can contain dangerous chemicals, the worth being the zinc-
formaldehyde-sulfoxylate (ZFS), a catalyst now widely prohibited as suspected of being
carcinogen in addition of irritation of the respiratory tract. Possible products of decomposition
include carbon monoxide, carbon dioxide, sulphur dioxide and zinc oxides. PEL and TLF for
sulphur dioxide is 2 ppm in any eight hours period (5ppm STEL).

A newer system is less dangerous: thiourea dioxide is the active ingredient replacing ZFS.
But this chemical have also its handling, environmental, and residual issues.
It is a strong oxidizer and must be kept in a sealed container.
When pouring the crystalline powder into the mixing container, efforts should be made to
minimize dust.
Adequate ventilation is recommended for any plant area should be sufficient enough for a
good air exchange rate.
Last point, but quite important : you must WASH the discharge printed garments before
packing

c) Problems related to dye undercoating

25    

During my audits, I found in India on organic cotton and in Thailand on polyester, problems of
loss of flexibility of the screen printed inks, breaking even respecting the relatively low
extension test of sportswear’ customers - now extension of 40% - after washing tests (5
washings) both for direct printing and transfers and also problems of migration of dye
inside of the printed screen inks (mostly with white printing turning pink or yellow).
It was quite clear for me that the problem came from the quality and technology used for
dying the materials.

A supplementary cause of poor adhesion (= ink breaking at extension) is the use of certain
additives such as softeners, anti-static, anti foam, etc. : if they contain even simple traces
of silicones, adhesion problems will occur.

I then received confirmation from diverse sources related to inks and dyes manufacturers
and printers from several parts of the world : they were unanimous to say that the screen
printing – direct or transfer - was not the cause, but that it was the quality of dyes and that
even to screen print an “anti-migration ink coat” was most often not sufficient!.

This can be summarized in the following manner :

- When printing on synthetics or diverse blends, polyester/cotton, polyester elasthane,
thermo migration can occur if low sublimation disperse dyes are used. Printing
on dark background (dyed) should be done only after checking quality of dyes used
etc. (high sublimation dyes cured above 185/195oC are recommended)
- While printing on cotton, fixation of reactive dyes can be a problem particularly with
cheaper monovalent dyes (this is specially true for the dyes containing
magenta or yellow cheap pigments.
- Poor fixation and washing can lead to loose reactive dye on the surface, which can
bring the reactive dye migration in the film of screen printed ink, directly printed or
transferred.
- The printer is expected to check - before printing of course - bleeding of
reactive dyed fabric in hot water at 60o C, or using a wiping the dyed textile with a
white cotton impregnated of isopropyl alcohol or better, ethyl methyl ketone.

d) Ink preparation and colour matching

As I seen above, I am not in favour of the use of “home prepared” inks. I saw too
many mixtures (pigments + base + additives) where the addition of those diverse
elements and additives was quite approximated. With a rheology out of control and
even sometimes the use of prohibited pigments containing heavy metals.
That is why, once more I advice to use ready industrially manufactured inks as the
ones mentioned above.
When several colours have to be mixed in precise percentages to obtain the wished
tint required by the customer, the most common is to carefully weigh each component
using an electronic precision balance (precision of one gr. and with a capacity of 5
kilos). The use of a viscometer can help if you want control and repeat the exact
wished viscosity which can be quite different for manual or automatic machine
printing.
To mix the colours, use a spatula if less than one kilo and use a mixer for the bigger
quantities – 5 kilos or more.
26    

Ink preparation bank

Once the correct colour reached (in general by visual comparison) NOTE the exact
proportions of each colour and the additives or/end diluters used, in a manner to
repeat exactly the formulation when a further reprint has to be done.

To control the exact colour is made most of time made visually. But, of course,
despite of the cost, the use of a spectro-colorimeter permits to obtain absolutely
precise data about the colour components of the ink.
If you print in four or six halftone colours to reproduce a photographic or complex
designed image, the control of the correct densities for cyan, magenta, yellow, black
and eventually orange and green, the use of a densitometer (spectro-densitometer)
giving the density and the percentage of dots is an obligation, despite of its cost.

In all cases, if a visual control is necessary or the only method usable, it is

absolutely vital to use a “light box”, giving at least daylight – more or less 5,000°
Kelvin – and “warm light” – more or less 3,200° K.

Light box for colour control

e) Colour proofing
Colour (and design) proofing is made to show the customer or his agent what he
will exactly get from both his art work and chosen colour on the precise material that
will be used to produce the whole run.
27    

Most of printers does it manually.

When the order will be printed on an automatic carrousel, it is better to do the

proofing on the press itself for keeping the same parameters.
A manual proofing will not be a warranty of the exact matching of the colour and
design details when printed on an automatic press.

Colour proofing

f) Storing the inks

I saw the best and the worth !
First of all, remember, as seen above, plastisols and water based ink should be
stored (and prepared) in separate rooms.

Despite this seems to be evident, it is clear that the pots, mixed or not, must be
cleaned before storing.
What we can see here below is exactly what must not be done:

Awful inks storage

2 – MANUAL PRINTING ON LONG TABLES OR MANUAL CARROUSELS

a) The long tables

28    

Manual printing on long tables

The use of long tables is not my recommendation - even when they use separates pallets or
an angulation of the tables of 30° to 40° which is clearly more ergonomic for the “printing
stroke effort” !

One other problem, both with long tables and carrousel, is the necessity to glue each “piece”
or “part” of garment exactly at the good place every time the image, text, logo or part of
image must be at a precise position because of the following sewing and mounting of
garments.
This make the setting and gluing of each peace a time and people consuming
operation: it is by nature a slow process.

Gluing and setting of each piece

Of course, I recognized that in many countries where the cost of labour is (unfortunately) low
or very low as well as the cost of floor space, compared with the cost of investments in
automatic press (whatever you call it “rotating” or “carrousel”).
29    

Angulated long tables with separate pallets (slightly better)

This means that for many companies (the exception was for me and amazingly Tirupur in
India, and Turkey with almost no one “long table”), the cost of the tables, even a little more
sophisticated that the simple flat tables and the employment of many peoples in one or two
shifts is so far a commercially cheaper option.

A fact I do understand of course…. BUT, Several things are difficult to swallow when I see
how the technology is used in this way !

Bad squeegees – unsharpened -, prints in 1, 2, 3 strokes even up to 5 (yes, I saw it !),

wet on wet or even after a flash curing.

Why ? : to be opaque enough I guess, but with the good ink, the good choice of screen, its
high tension and its stencilling, this bad practice is totally unnecessary and un-
appropriate :
one single stroke is mostly sufficient and, only if really necessary, a second one, only
after flashing.

Good manner to print Bad manner to print (and dry !)

The strokes – instead of being in the same direction - can even be back and reverse (the
worst), with poorly stretched screen and even wooden frames !
As a result, a good edge definition and sharpness of print is almost impossible.

Other problem : constancy, consistency and repetitiveness are at least….very difficult : first,
for the same person printing the same image or text at 8 AM and later at 5 PM… Or worst,
30    

when another person – from the second shift – replace the first one, he (or she) cannot have
exactly the same “hand”. Speed, angle, pressure of the squeegee vary enormously and this
is exactly a fact creating the type of problems that we don’t like to see in its prints.

This said, and if there is no other way to proceed, if high tensioned screen , with good
stencilling are used, if the squeegee blade are carefully sharpened and re-sharpened
when necessary, if the table or pallet is inclined at 40°, if one single squeegee stroke
is given (after flooding of course), if a careful control of quality is made during the working
day – each hour if possible – this type of printing can be used for simple logos, flat
colour or line printing, but remain totally prohibited when it is question to print halftone or
indexed colours !

The off-contact (distance between the screen and the printed material) can be reduced to
an absolute minimum with the high tensioned screens : between 1 to 2 mm. This is of
course much better to prevent image’ distortion or un-sharp printing.

Add the time to put the glue, the setting time necessary when you print only parts of clothes
(and not the mounted shirt), and I don’t speak of drying with a hair dryer or other primitive
systems…

The bad manner to “flash cure”: with hair dryers !

….the time to prepare a precise register from one piece to the next, even the necessity,
sometimes, to leave the print dry naturally in ambient air… And you will understand that
this form of printing is not exactly the one preferred for quality printing, constancy
and productivity.

b) The manual carrousels

The restrictions are identical than above – because of “manual printing” - with a slight
preference in term of speed and productivity. But, it remains clear that when you print not the
whole mounted garment or T-shirt, but the future garment part per part, the time needed
to glue and set precisely each piece makes it a slow process, despite a little faster than on
the long tables.
Remember, you can reduce a lot the off-contact, as above, with the very high tensions of the
screen.
31    

Manual carrousels

c) The automatic carrousels

Oval carrousels 8 and 10 colours

Multi- colours automatic carrousels

Some of those machine, often highly sophisticated of which the main manufacturers are M&R
(US), MHM (Austria), S-Roque (Portugal), TAS (Australia), Beck (Germany), 1DQRSULQ7H[RI
*UDILFD,QGLDand the number of stations (then colours) can vary between 5 and 18 which offer
a lot of possibilities in multi-colour jobs, halftone and indexed colours at speeds that can be above
1,000 pieces/hour. Such speeds are only possible when printing already mounted garments
(T-shirts for example) that can be quickly fed on the pallets.
32    

When those carrousels are used with “parts” that must be precisely glued at the precise
needed place, of course the speed fall down quite a lot and the quantities printed per hour fall
down between 100 and 300 pieces per hour, low speeds if compared with the possibilities of
the press, and highly depending upon the skill of the printers/feeders.

Diverse automatic carrousels from the main brands

d) Pre-setting and setting

33    

I prefer of course the use of “automatic carrousels”, for the simple reason than it is easy to
keep totally constant the speed of printing stroke, the pressure and angle on the squeegee
and on the flood-bar. This is a warranty, if properly set, of quality printing.

A precise “pre-register” of the films on the screens, in function of the number of colours
and of the carrousel itself is highly desirable because it saves a lot of time while setting the
screens on the press and looking for the precision of adjustment of the different colours the
perfect register.
It exist on diverse big brand of carrousels, automatic pre-registers systems, integrated or not,
the most famous being the Newman PinLock System. This one is specially adapted to the
use of the Newman Roller frames mentioned above for the very high tensions and the
maintaining of those tensions.
It starts with the film making, followed by the screen exposure and on-press alignment. For
multi-colour printing, more than 8 or 10 colours on automatic carrousels, it reduces the set-up
time to less than 15 minutes. Especially when used in combination with the “Swing-Out
Pallet” still of Newman.

Even when using less sophisticated systems, it is clear that a lot of time is saved when the
films are carefully positioned on the screens – in multi colour printing but also in single colour
before exposing the screens.

Pre-positioning the films in register with the screens

Of course, the setting can be adjust on most of multi-colour carrousels with the micrometric
register screws – three in general – positioned on each of the screens holders.

3 micrometric screws for register setting

34    

e) The off-contact
On the good carrousels, in additions of many possibilities of setting (register, squeegee and
flood bar angle and speed, thickness of material to print, etc.), the distance between the
under part of the screen and the surface of the material to print can be precisely adjusted.
This distance, the “off-contact”, can be reduced with the screen in the very high tensions –
above 25 Newtons/cm as seen above – at 2 and even 1 mm.
This prevent any image or design distortion and, in combination with the quality of the
stencilling and of the squeegee blade, a sharper and precise print.

It also allows what I appreciate and advice very much the “kiss printing” : it is not any more
necessary to put a lot of pressure on the squeegee which bend the blade and engender an
un-sharp print. As a lower pressure is necessary to put the screen in contact with the
material, the quality of image improves.

f) The squeegee, choice and preparation

Here again we find a most important tool about many printers are ignorant of or even seem to
despise it ! I saw so many companies not knowing or willing to know that a squeegee blade
must be perfectly sharpened (and re sharpened as often as necessary) to allow a good
printing.
I audited 44 companies in 6 countries. 23 of them had no squeegee sharpening
machines ! more than half of them which is for me incredible!
Here again we find, after the problems related to a poor tension of the screen, the second
main reason of the poor quality of many prints.
When I ask, “but what do you do when the squeegee blade is damaged, or too short, or has
notch or jaggedness ?”… They answer, “we change it and put a new one !”.
Of course they ignore that most of new blades need also a slight sharpening before use !
Many times, the squeegees are not properly looked after, cleaned, stored and so on…

Different models of squeegee sharpeners, simple or very sophisticated, from Grafica

(left) and Fimor (2 on the right)

Despite what too many screen printers in the world believe, the squeegee do not “press the
ink through the screen fabric”. The squeegee “put the under side of the screen in close
contact with the surface of the material to be printed”.
The ink inside of the screen fabric is then “transferred” by capillarity on the material.
This means that the deposit of the ink made onto and in the screen – on the automatic
carrousels – by the flood bar is extremely important : it must “feed the fabric” and not stay
in heavy deposit on top of it.
Any damage on the squeegee or/and flood bar (notches) will be reflected on the ink deposit,
then of course on the image or text printed.
As, in manual printing the squeegee is used both to print and to flood, the traces left by the
damaged blade have a kind of “double effect” !
35    

Different squeegee sharpeners saw around…. More or less good !

That is why it is vital to have a squeegee blade in perfect condition from the
beginning to the end of the run.

This said, the questions remaining will also be :

What “shape” for the blade ?
What “hardness” – shore degree – for the blade.

- The shape
There are most often three blade shapes used in textile printing :
Normal 90° angle - Simple bevelled angle – Double bevelled angle.

Despite several printers use for manual printing (long tables or manual carrousels) the
double and simple bevelled angles, I prefer and advice, as well for manual as for automatic
printing, the classical and normal 90° angle. Extremely well sharpened as seen above, of
course. The thickness of the blade is better in 9 mm (rather than 5 mm), with a height of 5
cm of which 2,5-3 cm are the “useful part”, from 2 to 2,5 cm being inside of the squeegee
holder. When it remains only 1,5 cm of blade, change it. If not, the internal suppleness, the
shore degree, will change and become too hard for a good print.

90° “normal” - Double and Single and triple shore squeegee for automatic
simple bevelled angles carrousels

- The hardness – shore degree

Most of squeegee blades are “simple shore”, most often in textile printing, 65° and 75°
shore. Normal prints are made using a 75° squeegee and thicker coat of ink using 65° which
is slightly softer.
A good solution is, on the automatic carrousels, the use of “triple shore”. A good solution is
the use of “65°-90°-65° shore” : the internal part in 90° shore - very hard then – bring a
rigidity which prevent bending, even at high speed. The external parts in 65° shore are the
“printing lips” in contact with the screen surface that allow a soft and smooth quality of print.
It also exist in 75°-90°-75° that can be useful for some applications or bigger sizes (some
oval carrousels allow to print pieces of 80 x 120 cm).
36    

Above, triple shore 75-90-75

Under, triple shore 65-90-65

The main brands on the markets are French (Fimor), English (Ulon), German, US, etc…
My favourite and far the best brand is Fimor, best quality (totally controlled).
The blade are named “Serilor”

g) Flood-bar
The flood-bar, of course is a tool used only on the automatic carrousels. It can be in
aluminium, stainless steel or blue steel or, in some brand simply another “printing” squeegee.

Flood-bars for automatic carrousels

Personally, I like the blue steel of 500 microns, this type of flood-bar giving a better control of
the ink flow. Remember, the ink deposited on and in the screen by the flood-bar is the one
that will be transmitted to the printed material by capillarity when the squeegee blade put in
contact the screen and the substrate.
The flood-bar blade must be perfectly sharpened and the edge must at the same time “soft
like a baby skin” !
If the squeegee blade has notches, it damages the print. If the flood-bar has notches, it will
definitely damage the screen fabric itself.

h) gluing the material, pieces or full garment with adhesive

Here are several possibilities.
The question is “how to deposit glue on the tables or on the pallet with both precision
and cleanliness” !
When a full garment is printed a T-shirt for example, its easy because the whole pallet can
be glued. Some sophisticated automatic carrousels have even an “automatic gluing
system”… But this is not common at all and not very practical if you print cut pieces.
37    

The bad response is to put the glue (adhesive) with a spray.

Of course, it is easy, quick, simple and so on and some manufacturers pretend to supply you
with sprays containing “ecologic adhesive”…. But we don’t like it at all as being
dangerous for the peoples working in the plant because whatever can be the cautions
taken you should be surprised by the look of your lungs ! after a few months !
Plus the danger to glue small particles of cotton that will then stick everywhere inside of the
plant, on the machines included… on the material printed or to print, and again, in the lungs !
Please, forget the spray.

Spray = NO

Then you have the “recommended” solution (but not the best): the “brush”.
A part of the problem is related to the necessity to put the glue very precisely when you will
have to print pieces of very different shapes and sizes.
For me, this procedure is slow and complicate :
- first step, you have a model (generally in paper) of the cut shape of the piece to print, once
cleaned the table or pallets of the preceding shapes, you report his contour with a pen or or
chalk or something similar
- second step following (more or less) the design, you brush the space with adhesive.
- last step, you put and glue each piece exactly at the correct place.

Design to brush the adhesive and put the piece in register

I have a quicker, simpler and much more precise manner to put the adhesive : screen
print it !
You make a screen with the exact shape of the textile piece, simply 2 or 3 mm smaller all
around and you print it on the tables or the pallets using a screen printable non permanent
adhesive, generally water based and using your screens register system along the table.
38    

Same thing on the carrousel, you can use one of the remaining available post and, from time
to time, you put a new coat of adhesive when the precedent is not gluing anymore.
Another good idea is to give a ligh coloration to the adhesive to print to make it more visible
on the pallet or table. You save the time of designing and the time of brushing.

i) Printing, flashing, curing drying technologies in general

About printing, I already gave many indications when speaking of screens, inks,
squeegees…
Printing manually or automatically should require only one squeegee stroke. Never, as I saw
too often, two or even three or more ! Wet on wet and even in the two directions.
How can you expect, especially with screens having most of time a poor or extremely poor
tension - less than 10 Newton/cm – to obtain a clear and sharp printing with a good edge
definition !.
If, for reason of opacity of a light or bright colour printed on a dark dyed material, cotton or
polyester, 2 printing strokes seems an obligation, it is better to flash cure the first
printed coat before applying the second coat.

Light colour printed twice (manual and automatic) with intermediary IR flashing

Don’t use, once more, as I saw too many times, hair dryers : impossible to control and to
have constancy added to the need of one person to do something that can be done
automatically.

Automatically moving flashing units

When printing manually or automatically – remember, with a normal (90°) squeegee blade,
having a suppleness of 65°, 75° or triple shore – it is better to keep a printing angle, most of
times, of 75° between the frame and the squeegee (90° being the “vertical” as a reference).

Remember that more pressure does not increase the ink deposit, it simply increase the “line
of contact width” between the screen and the printed material, especially with a badly
stretched screen and then engender – again – an un-sharp print with a poor edge definition.
39    

75° for squeegee angle while printing

Flooding must be done by just filling (and feeding) the fabric of the screen : no thick over
coat, not too much pressure – be supple and soft.
Flash curing is also used quite a lot on carrousels, manual or automatic, either to obtain a
partial drying before the addition of a second coat of ink on the same logo or text, or to flash
cure a first white when printing halftone image on dark material, and, often a second flashing
after CMYK before printing a white for high lights.

IR Flashing units on carrousels

Generally, “flashing” is not sufficient both to create a perfect drying – and polymerisation – of
the inks and also their resistance to washing or dry cleaning. To make of the printed textile
what we name a “fast colour” (“grand teint” in French), a heating made either by hot air
pulsed units or better by infrareds (IR) radiations at temperature which can be between 130°
and 180°C, according to the type of material cured. It is evident that cottons can and must be
cured at a much higher temperature than polyester or polyamide.

Textile dryers

Personally, I think that the IR (infrared) dryers are more stable, controllable and efficient that
the jet-air, but both, unfortunately, are big “energy consumers” engendering in addition a high
40    

additional temperature inside of the printing plant a fact which is not so much appreciated in
the hot countries. That is why a part of the textile printing future relay on the water based UV
inks technology… So far, another story !.

Other type of dryers, air jets and IR

D - RELATED TECHNOLOGIES

a) Printing and curing the flock

Flocking is a technology often added to the “normal prints” and that can now be classified in
the category of “special effects”.

Flocking implies first to screen-print an adhesive – varnish-glue type – on the material.

This adhesive often receive a certain amount of pigment or dye to become in a similar colour
to the one of the flock fibres applied, this to engender a better harmony of colour on the
flocked textile especially when there are huge differences between the colour of the flock and
the colour of the material.

Then, immediately following on the long-table, the flock-fibres are deposited on the
adhesive using electrostatic energy to send the fibres charged with an opposite sign of
electricity on.

Those fibres have multiple possibilities in colour, length and nature, the most popular being
acetate of a length inferior to 1 mm.

This operation can be also done in separate special equipments, box or even, in a special
installation by “blowing” the flock onto the adhesive…. (this last technique being certainly
not the best solution !).
41    

Printing the adhesive and flocking

Air pressure flock cabinet Intermediary drying with hair dryer

After that, the flocked print is dried - infrared or hot air – at a temperature between 140°C and
180°C, depending upon both the quality of fibres, of the material and of the adhesive.

Independent flocking units (electrostatic) Drying and curing flock

The last operation – very important – is the “brushing of flocked textile”, brushing under a
strong air aspiration, to eliminate the non fixed fibres and prevent the risk to see the fibre in
excess to be inhaled or swallowed by the peoples working in the plant and of course the end-
users.

To use longer fibres, on cotton or polyester, will often engender a poor resistance to washing.
Of course “flock on flock” is stupid and cannot have any good resistance. I saw it and the
result was extremely bad !
42    

Of course, as seen above, a minimum of precautions must be taken a mask for the
printers is a necessity, extremely good ventilation of the whole part of the plant
dedicated to flocking is an obligation.

For reason of health of course, but also to prevent the presence of flock fibres in the air of the
whole plant could also be damageable for the “normal” screen printed items, with coloured
fibres that could pollute the fresh prints before dried.

Flocked black on water based coul. Full coloured flock on shirt

b) Washing and elasticity tests – control tools

Those tests have to be made for each new order or each repeated order in a manner
to be sure that the parameters accepted by the customer are the good ones and did
not change in case of reprint.
Generally, the customers requires between 5 and 10 washing tests at 50-60°C
during 15 to 20 minutes for each with, if possible, an intermediary drying between
each.

Washing machines

Second important test : elasticity

An other important test where is measured the resistance to “traction-extension” of
both directly printed and transferred images, logos, designs, on different types of
textiles : cotton, polyester, polyamide, mixed, elasthane, etc. To do in warp and weft.
43    

The extension tests are now limited to 40% = extension of 4 cm for 10 cm. Higher
extension being meaning less if referred to a normal use of those sport-wears.

There are also other tests for resistance to pressure, chocks, rubbing, scratching,
colour resistance and light fastness, accelerated weathering tests, ironing, colour
control as seen above using the eye and a simple light box, or more sophisticated
tools such as spectro-photo colorimeters and or densitometers, etc.

Diverse control tools

c) Treatment of the spoiled water

This depends of course of the size of the plant. It is clear that if you need to dye huge
surfaces of textile, and at a smaller scale – in terms of water consumption – clean
and reclaim hundreds of frame (screens) each days, you will need a big (and
expensive) unit for the treatment of water.
44    

Big water treatment unit

At the contrary, a small printing plant using only a few hundred litres/day will need a
much smaller adapted unit.

Small unit for water treatment

In the actual preoccupation of “producing green products in a green manner” this

point is of huge importance for the end-users and customers in the field of sport-
wears, put a great pressure on this specific point.

At FESPA, the World Federation for Screen and Digital Printing, we also insist a lot
on this necessity of respecting the environment – we produced a brochure, “Planet
Friendly”, that I wrote together with the English specialist Paul Machin, explaining
what is pollution of air, water, wastes and how to get rid of it, energy and
environment management.

This brochure is free for the members of National associations belonging to

the Federation FESPA (all the European countries, Turkey – full members - and
Australia, India, Thailand, China, Philippines, Japan, South Korea, Sri-Lanka, Tibet,
Mexico as Associate members).
So check if your company is member of your National Association, itself being
member of FESPA.
45    

The FESPA Planet Friendly Guide

For the screen printing plant, there are a lot of suppliers in different countries able to
deliver equipments for water treatment – the major problem in textile printing –
adapted to the size of the plant, the amount of water to be regenerated and the
financial possibilities of the company.
The purpose is to eliminate the polluters dangerous for human and aquatic organisms
and, in some countries, you now are obliged to reject only “chemically clean water”
in the city sewage systems.

The purpose is to eliminate the SS (Suspended Solids) and to reduce the BOD
(Biological Oxygen Demand) and COD (Chemical Oxygen Demand) to a “legally
acceptable level for health and environment”.

The flow of spoiled water (effluent) is due, in textile printing, at 60% in water based
inks cleaning, 10% in screen emulsion washing and 30% in screen reclaiming
(screen emulsion reclaiming, sometime combined with inks cleaning.

 
Automatic screen reclaiming machines

The characteristics of the effluent before disposal can contain components forming
three main groups:
46    

• SS of a size greater than 10 nanometres (ink residues for example) Colloidal

materials are SS of the same origin but of a size less than 10 nanometres (residues of
polymerised emulsion for example)
• Dissolved materials of less than a few nanometres, are generally cations and
anions as well as organic components (diverse solvents and detergents)
• Sometimes sewage treatment organisations put a limit on the
acidity/alkalinity (pH) of the discharge; it usually ranges from 6 to 8.

If you make you “silvered” films by yourself (with an “image setter” for example), you
must either have a “silver treatment unit” or let your supplier of photo films and
chemicals recover and retreat those effluents. As it contains a lot of recoverable
silver, this operation is self paying or even profitable.
Techniques such as CTS (direct from Computers to Screen) or ink-jetted films (but
take care of the definition and opacity) can prevent this kind of problems related to
production of effluents containing silver.

The techniques in use can be based on filtration, flocculation + micro filtration,

bore hole, closed or semi-closed circuit for washing and reclaiming with reuse
of grey water for reclaiming.

These last technology is provided by some manufacturers selling more or less

“automatic systems” for screen washing and reclaiming.

A “gravel trap” under the discharge point can be useful to reduce the SS.

The “reed bed” (I saw it in some places) is an engineered method of treating

pollutants using a biological planting containing typically the common reed,
Phragmites australis. The reeds pass oxygen, absorbed by their leaf system, via their
stems and rhizomes to their roots - the Rhizosphere.
Polluted water passing around the roots is purified by the immense population of
microorganisms living in the Rhizosphere.

“Reverse osmosis” an other technique, quite classical, is a separation process that

uses pressure to force a solution through a membrane that retains the solute or
particles on one side and allows the pure liquid to pass to the other side. The
membrane here is semi-permeable. The membranes used for reverse osmosis have
a dense barrier layer in the polymer matrix where most separation occurs.
Its achieved environmental benefits is that it removes almost all the pollutants.

d) About the transfers

1) Transfer printing
Some companies, in diverse countries, print their own transfers and sometimes
also print transfers for other companies.

Two sorts of transfers are used :

 adhesive heated transfers, for all types of textiles
 sublimation transfers for textiles containing a minimum of 70%
polyester
-
- adhesive heated transfers
They are mostly screen printed, using the graphic screen printing technology.
The printing presses are different and more related to graphic screen printing :
47    

with flat bed press, semi- or fully automatic, cylinder automatic press.

Types of press to print transfers : flat-bed and cylinder

Drying/curing are similar : Infrared; hot pulsed air, may be soon UV technology.

The key words are edge definition, constancy and repetitivity of the print, solidity
of adhesive, response to the correct criteria (temperature, pressure and length
of application), elasticity, washing and light resistance of the printed ink.

Almost any directly printed “special effect”, can be produced in transfer : glitters,
pearls, some high densities, metallic, reflective, foils, etc.

Printed sheets with transfers and foils effect by transfer

48    

The inks and adhesives are generally water-based and sometimes plastisol
and the printed substrate (provisory substrate) is either a silicone-paper – most
often T73 from Arjomari (France), or diverse sorts of polyester, grained or
smooth of thickness varying between 150 and 300 microns.
Those substrates allow the print to leave easily their “provisory” support to be
transferred on textiles through application of heat at a certain pressure.

According to the desire of customer and applicator, those can be “Hot transfers”
– this means the provisory support can be peeled immediately after application –
or “Cold transfers”, where the paper or polyester provisory support is peeled
after cooling, that is to say after a few minutes.

- Sublimation transfers
Those transfers can be screen, offset or digitally printed and refer to what we
name “dye sublimation”.

Digital press used for transfer

The ink, when heated on the press, turn into a gas which will transfer colours and
image on the textile.
This type of transfer which can be made in small or quite big size, works only on
fabrics containing 70% of polyester or polyamide, which means that it does not
work on pure cotton.

2) Transfer application
The printer or supplier of the hot transfers usually give the specifications for
transfer on different textiles
The parameters are heat, pressure, length of time for application).
Don’t forget those 3 main points, they are the KEY of success.

Unfortunately, the indications given by the manufacturer/printer of the transfer are

made with generally one type of press, in some conditions of temperature and
hygrometry, with a lack of covering of the under and upper plates – or the contrary
– with a rubber of such or such durometer (this durometer changes normally
according to the type of textile to be transferred), with a well balanced pressure,
etc.

All those given parameters are not so easy to respect in some specific conditions
and countries, and I saw so many different machines, manners to work, local
conditions, pottering and do-it yourself with good, acceptable, bad or very bad
inspiration which turn often the whole thing in an uncontrollable technology.
49    

The problem is often that from the transfer applier point of view, there are a lot of
transfer press on the market. As this is a tool of which the construction is quite
simple, for most of them, each country build models more or less sophisticated….
And more or less valuable ! There are European, Japanese, US press of course,
but also an incredible lot of Chinese, Indian, Thai, Turkish, Taiwanese, Brazilian,
Tunisian, ones.

The quality of those so diverse equipments in technology, size, complexity or lack

of it, etc. is extremely diverse. Contrarily to the choice of some equipments and
machines in direct screen printing, we cannot give a precise recommendation in
this field.
We cannot impose one single type of transfer press for this technology very much
in use because supposed to be more simple and controllable than “direct screen
printing”.

The sizes are also very different from some few cm2 to m2. As well as the
technical principle from flat bed to cylinder press for transfer applications, with one
single plate to three or even more, from one head to double head, from air to
mechanical pressure, from a central single piston to double, triple or more.
50    

A lot of different pransfer press !

This, plus some other factors not quite controlled makes quite often of
transfer application a nightmare for the company and huge problems for
the customer, even when he supplies himself the transfer, then with a “pre-
supposed good quality”.
Here, I don’t even speak of some companies making total or partial (first
stroke) transfer application through “ironing” ! Incredible but true – I saw it
– this being of course a practice preventing any kind of control and
constancy.

In addition, transfer remains for me a “slow process” if compared with

direct printing. People believe it is “safer” in term of image quality,
adhesion and elasticity…. Nothing is warranted !
51    

If the print is bad, un-sharp with a poor edge definition, if some precautions
have not been taken about the choice of inks, of transfer paper or
polyester, the thickness of ink deposit, the final protection of the adhesive
coating have not been respected, the result can be awfull.

The “large” transfer press, flat bed or cylinder press, are also numerous and of
very different qualities.

Big size transfer press

52    

a) Problems related to the press themselves

One of those problem is the difference of temperature between the one
displayed and the real one which changes during the day in the upper plate,
the one giving the pressure and heat on the transfer and most often in the
under plate by heat accumulation during the working hours.
The problem is that, in one hand, this “parasite additional heating” changes
the temperature of application and that, in the other hand it heats the transfer
from the textile side which is a source of adhesion problems.

Two solutions :
- One would be to change the under plate, generally made of iron, steel or
aluminium, all conductive materials against a non conductive (ot electricity
and heat) ones and for cost reason, the most adapted is the very hard and
rigid wood complex named “Medium” of 18 to 24 mm thickness.
It can easily replace the metallic base.

Many people think too often that the rubber plate added on the under plate –
red or black, (black being the worth because heat absorbing) – is a sufficient
insulating substance. It’s not true ! and the addition of single or multi layers
of textile material does not help much.

- The second one – an evidence of course – is to verify each hour the exact
temperature between the two plates with an external thermometer.
-

Measuring the existing “real” temperature during the working hours

As a result, this means that you must adjust each hour the displayed
temperature of the transfer press to “compensate” the accumulated added
heat and respect the temperature given by the transfer manufacturer.

Other problem: the number of piston, one, two, more, depending upon both
the type and the size of the transfer press.
It is often difficult to precisely “balance” the pressure on those different
pistons. Here again, it depends of the quality of construction of the machine
and many “locally built or home made machines” do not offer this stability.

b) problems related to the “use of the press”

A good example is the fact that even the smallest press (A4 or a little less)
many transfers of logos or small texts are of a surface of only a few cm2 the
users either add a small piece of rubber under the place where the transfer
must be attached.
53    

Or, other users will try to mount several transfers on the same (often bigger)
plate.
In the first case, the pressure parameters have to be changed and it is
absolutely necessary to carefully “smooth” the edges of the small rubber
piece to prevent a mark – lustring or glazing - on some textile (polyester
or/and elasthane for example)

Sharp edges of rubber Smoothed edges of rubber

In the second case, it proves itself extremely difficult “to balance” the
pressure in a similar manner in each part of the plate.
Of course the user will say that it increase the production… That’s an
evidence, but it is at the detriment of quality and constancy, two main points
for the final customer !

Multi simultaneous transfers, bad solution for constancy

And also difficult to have exactly the same temperature for each small
transfers put on a single big base.

c) Problems related to … bad habits or “improvisation”

I saw a lot of “strange practices” which looks more like desperate attempts to
achieve a good result by trying a lot of supposed “improvements” !
A kind of “black magic tricks” !

One of those is the addition of pieces of textile over the rubber on the
under plate and even sometime on the upper “heating part”…. No one
could ever give me a logical explanation. It can be one single thickness,
several thicknesses, different sorts of fabrics, etc…
54    

Please, take this “clothe” off !!

A use of the rubber pieces with no care of its internal suppleness is

another cause of problems : the “shore degree” (internal suppleness) of the
rubber must be adapted to the to the textile receiving the transfer.
Question of practice, with as a basic rule of 75° shore for thick cotton or
flannels and only 45°/50° shore for thin polyester and elasthane.
The blended material need the use of intermediary suppleness… Too many
possibilities to give precise rules. It can also depends of the thickness of the
rubber : the solution goes through testing and proofing diverse rubbers to
choose the one able to give the optimal result.

d) Problems related to dyeing and other “pre-treatments”

As I widely describe this problem in the “Direct Printing” part, please refer
above, page 27 in: 1. CHOOSING THE INKS – c) Problems related to
dyed undercoating

e) Register and productivity, other uses of transfer press

An other sometimes slow and obsolete technology : in many companies, the
peoples working on the transfer press work using such strange technique as
registering with a piece of pre-cut paper.

Manual register for transfer

This is a slow technique which increase even more the length of production of
transfer = a low productivity.

It exists now much faster techniques allowing to register quickly and

accurately using a red laser light programmed to show exactly the position of
the big or small transfer.
The lines for accurate placement and registering of the transfer – or other
applications with or without transfer such as embossing effects – appears on
55    

the pieces of textiles to decorate as a red line with cuts or references

allowing a bi-dimensional precise setting.

This allows to set the transfer at its correct position three or four time faster
than with the cut paper.

The cost of such an installation being relatively low, the return on

investment is extremely quick if taking into account the time saved.

Laser registering of normal transfer and embossed transfers or prints

f) Improving the quality of transfers

The two main problems remains the adhesion of the transfer on the fabric
and its elasticity.

There are solutions to improve significantly those two points.

One is to add by lamination a supplementary adhesive coat to increase the

“tack” of the adhesive of the transfer and also its “global suppleness”.

The other, when for example we speak of “foil transfer”, is the use of the
best brands of adhesive decals such as the one supplied by 3-M. Of course,
the price is higher, but the “safety at work” and the “satisfaction of the
customer” compensate widely this over-cost.
This is my belief and what I preach for : quite often to pay a slightly
higher price at the production allows to save a lot in rejects, controls,
quality of production… and final satisfaction of the customer.
Finally this so called “over cost” reduces the total amount of money invested in
a production.

This re-enforce my concept of neglecting what we can call the “immediate

profit” (by using or buying cheaper products) which save only a few cents but
permit to make a much safer “global final cost” of the product for the customer.

Michel Caza
International Consultant, FESPA Board member, Academy of Screen and Digital
Printing Technology Past Chairman
Revised December 1 – 2017