PREPARATION OF PAINT PIGMENTS
A CHEMISTRY PROJECT REPORT
Submitted by
B. AVINASH, CLASS XI
SRIMATHI SUNDARAVALLI MEMORIAL SCHOOL
CHENNAI - 600063
Table of Contents
Serial Sub-Topic Page
Number Number
1 Acknowledgement 3
2 Abstract 4
3 Introduction 5
4 Principle 10
6 Requirements 11
7 Procedure - 1: Prussian Blue 12
8 Procedure - 2: Chrome Yellow 14
11 Conclusion 17
12 Precautions 18
13 Future Scope 19
14 Bibliography 20
Page 2 of 21
Acknowledgement
I would like to express my sincere gratitude to my school, Srimathi Sundaravalli
Memorial school; and my chemistry teacher, Mrs. Divya, for encouraging me to
do this project of Preparation of Paint Pigments, and moreover for giving us
guidance and moral support, all throughout this academic year. This project has
given me a deeper understanding of modern chemistry. Secondly, I would also like
to thank my parents for providing me with the required resources and
encouragement for the completion of this project. Furthermore, I would like to
thank Nishanth, Raghul, Tejas for providing me with the necessary details and
helping me in carrying out the experiment.
Thank You,
Avinash B
XI – C
Page 3 of 21
Abstract
This topic was chosen because of the fascination and the science behind the
working of a pigment, and how the colour of each pigment is different and has
different shades of the same colour. We wanted to know how to prepare paint
pigments using various chemicals and record the efficiency in producing them.
Pigments are insoluble particulate materials that provide colour, opacity, gloss
control, rheological control, and certain functions such as corrosion inhibition or
magnetic moment. They also reduce the cost of coatings by acting as a volume
filler.
Page 4 of 21
Introduction
What Are Pigments?
A pigment is a material that changes the colour of reflected or transmitted light as
the result of wavelength-selective absorption. This physical process differs from
fluorescence, phosphorescence, and other forms of luminescence, in which a
material emits light.
Many materials selectively absorb certain wavelengths of light. Materials that
humans have chosen and developed for use as pigments usually have special
properties that make them ideal for coloring other materials. A pigment must have
a high tinting strength relative to the materials its colour. It must be stable in solid
form at ambient temperatures.
For industrial applications, as well as in the arts, permanence and stability are
desirable properties. Pigments that are not permanent are called fugitive. Fugitive
pigments fade over time, or with exposure to light, while some eventually blacken.
Pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food, and other
materials. Most pigments used in manufacturing and the visual arts are dry
colorants,
usually ground into a fine powder. This powder is added to a binder (or vehicle),
a relatively neutral or colourless material that suspends the pigment and gives
the paint its adhesion.
Page 5 of 21
Page 6 of 21
A distinction is usually made between a pigment, which is insoluble in its vehicle
(resulting in a suspension), and a dye, which either is itself a liquid or is soluble in its vehicle
(resulting in a solution). A colorant can act as either a pigment or a dye depending on the vehicle
involved. In some cases, a pigment can be manufactured from a dye.by precipitating a soluble
dye with a metallic salt. The resulting pigment is called a lake pigment. The term biological
pigment is used for all colored substances independent of their solubility.
Page 7 of 21
More about pigments
Pigments appear the colour they are because they selectively reflect and absorb
certain wavelengths of visible light. White light is a roughly equal mixture of
the entire spectrum of visible light with a wavelength in a range from about 375
or 400 nanometers to about 760 or 780 nm.
When this light encounters a pigment, parts of the spectrum are absorbed by the
molecules or ions of the pigment. In organic pigments such
as diazo or phthalocyanine compounds the light is absorbed by the conjugated
systems of double bonds in the molecule. Some of the inorganic pigments such as
vermilion (mercury sulphide) or Cadmium yellow (cadmium Sulphide) absorb
light by transferring an electron from the negative ion (S2-) to the positive ion
(Hg2+ or Cd2+). Such compounds are designated as charge-transfer complexes, with
broad absorption bands that subtract most of the colour of the incident white light.
The other wavelengths or parts of the spectrum are reflected or scattered. The new
reflected light spectrum creates the appearance of a colour. Pigments can only
subtract wavelengths from the source light, never add new ones.
The appearance of pigments is intimately connected to the colour of the source
light. Sunlight has a high colour temperature, and a fairly uniform spectrum, and is
considered a standard for white light. Artificial light sources tend to have great
peaks in some parts of their spectrum, and deep valleys in others. Viewed under
these conditions, pigments will appear in distinct colour.
Colour spaces used to represent colour numerically must specify their light
source. Lab colour measurements, unless otherwise noted, assume that the
measurement was taken under a D65 light source, or "Daylight 6500 K", which
is roughly the colour temperature of sunlight.
Page 8 of 21
Other properties of a colour, such as its saturation or lightness, may be determined
by the other substances that accompany pigments. Binders and fillers added to
pure pigment chemicals also have their own reflection and absorption patterns,
which can affect the final spectrum. Likewise, in pigment mixtures, individual rays
of light may not encounter pigment molecules, and may be reflected as is. These
stray rays of source light contribute to a slightly less saturated colour. Pure
pigment allows little white light to escape, producing a highly saturated colour. A
small quantity of pigment mixed with a lot of white binder, however, will appear
desaturated and pale, due to the high quantity of escaping white light.
Selection of a pigment for a particular application is determined by cost, and by
the physical properties and attributes of the pigment itself. For example, a pigment
that is used to colour glass must have very high heat stability in order to survive
the manufacturing process; but, suspended in the glass vehicle, its resistance to
alkali or acidic materials is not an issue. In artistic painting, heat stability is less
important, while light fastness and toxicity are of great concerns.
Page 9 of 21
In biology, a pigment is any coloured material of plant or animal cells. Many
biological structures, such
as skin, eyes, fur, and hair contain pigments (such
as melanin). Animal skin coloration often comes about through specialized cells.
called chromatophores, which animals such as the octopus and chameleon can
control to vary the animal's colour.
Many conditions affect the levels or nature of pigments in plant, animal, some
Protista, or fungus cells. For instance, the disorder called albinism affects the
level of melanin production in animals.
Pigmentation in organisms serves many biological purposes, including
camouflage, mimicry, aposematism (warning), sexual selection and other forms
of signaling, photosynthesis (in plants), as well as basic physical purposes such
as protection from sunburn.
Pigment colour differs from structural colour in that pigment colour is the same for
all viewing angles, whereas structural colour is the result of selective reflection or
iridescence, usually because of multilayer structures. For example, butterfly wings
Page 10 of 21
typically contain structural colour, although many butterflies have cells that
contain pigment as well.
Principle
The principle behind the working of pigments is related to how different
substances could selectively absorb and reflect different light rays corresponding
to their different wavelengths in the visible spectrum. Pigments appear the colour
they are because they selectively reflect and absorb certain wavelengths of visible
light. White Light is a mixture of all light rays of wavelength 400 nm – 700 nm.
When this light encounters a pigment, parts of the spectrum are absorbed by the
different components of the pigment.
Some other wavelengths or parts of the spectrum are reflected and scattered. The
new reflected light spectrum creates the appearance of a colour. When this
reflected light meets a Human Eye, the Brain perceives the light as the colour
corresponding to its Wavelength.
Pigments, unlike fluorescent substances, can only subtract wavelengths from
the source light, and can never add new ones.
Page 11 of 21
Aim of Experiment
To prepare paint pigments using various chemicals and reagents.
Requirements
Apparatus Required:
1. Filter Paper
2. 250 ML Beaker
3. Conical Flask
4. Funnels
5. Distilled Water
6. Electronic Weighing Scale
7. Spatula
8. China Dish
Chemicals Required:
Experiment 1: Prussian Blue
Ferric Chloride and Potassium Ferrocyanide
Experiment 2: Chrome Yellow
Potassium Chromate and Lead Nitrate
Page 12 of 21
Procedure
Experiment 1: Preparation of Prussian Blue
1. Make a solution of hydrated iron (III) chloride by dissolving 5 grams of
the salt in 50 mL of water. Stir the solution briskly, using a spatula, until
the salt particles are properly dissolved in the water.
2. Make a solution of potassium ferrocyanide by dissolving 10 grams of salt
in 75 mL of water. Stir the solution briskly, using a spatula, until the salt
particles are properly dissolved in the water.
3. Add iron chloride solution, slowly, into potassium
ferrocyanide solution while stirring briskly.
4. Leave the dark blue (Prussian blue) mixture, so formed,
undisturbed for 15 minutes.
5. Prepare a gravity filter by setting a folded filter paper in the form of a
cone, which is stuck to the inner edge of a funnel, which is then set on a
conical flask.
6. Pour the mixture, slowly, over the gravity filter, and allow the powder
to precipitate.
7. Once the filter paper is dried up, carefully remove the filter paper, and
pour the powder in a China dish.
8. Scrape the excess powder that is stuck on the filter paper, by using a
spatula.
9. Obtained is the paint pigment of the shade Prussian blue.
10.Weigh the powder formed on an electronic weighing scale and
calculate the efficiency of formation.
Reaction Involved: 3K4[Fe (CN)6] + 4FeCl3 → Fe4[Fe (CN)6]3 + 12KCl.
Page 13 of 21
Page 14 of 21
Experiment 2: Preparation of Chrome Yellow
1. Make a solution of potassium chromate by dissolving 7 grams of the
salt in 50 mL of water. Stir the solution briskly, using a spatula, until
the salt particles are properly dissolved in the water.
2. Make a solution of lead nitrate by dissolving 10 grams of the salt in
100 mL of water. Stir the solution briskly, using a spatula, until the
salt particles are properly dissolved in the water.
3. Add potassium chromate solution, slowly, into lead nitrate solution
while stirring briskly.
4. Leave the yellow (chrome yellow) mixture, so formed,
undisturbed for 15 minutes.
5. Prepare a gravity filter by setting a folded filter paper in the form of a
cone, which is stuck to the inner edge of a funnel, which is then set on
a conical flask.
6. Pour the mixture, slowly, over the gravity filter, and allow the
powder to precipitate.
7. Once the filter paper is dried up, carefully remove the filter paper,
and pour the powder in a China dish.
8. Scrape the excess powder that is stuck on the filter paper, by using a
spatula.
9. Obtained is the paint pigment of the shade chrome yellow.
10.Weigh the powder formed on an electronic weighing scale and
calculate the efficiency of formation.
Reaction Involved:
K2CrO4 + Pb (CH3COO)2 → PbCrO4 + 2 CH3C
Page 15 of 21
Page 16 of 21
SOME OF THE PIGMENTS
Page 17 of 21
Conclusion
Pigments are completely or nearly insoluble and chemically unreactive in water or another
medium; in contrast, dyes are colored substances which are soluble or go into solution at some
stage in their use. Dyes are often organic compounds whereas pigments are often inorganic.
Each pigment has a generic index number that identifies it chemically, regardless of proprietary
and historic names. For example, Phthalocyanine Blue BN has been known by a variety of
generic and proprietary names since its discovery in the 1930s. In much of Europe,
phthalocyanine blue is better known as Helio Blue, or by a proprietary name such as Winsor
Blue. An American paint manufacturer, Grumbacher, registered an alternate spelling (Thanos
Blue) as a trademark. Colour Index International resolves all these conflicting historic, generic,
and proprietary names so that manufacturers and consumers can identify the pigment (or dye)
used in a particular color product. In the CII, all phthalocyanine blue pigments are designated by
a generic color index number as either PB15 or PB16, short for pigment blue 15 and pigment
blue 16; these two numbers reflect slight variations in molecular structure, which produce a
slightly more greenish or reddish blue.
Around 7.4 million tons of inorganic, organic, and special pigments were marketed worldwide.
According to an April 2018 report by Bloomberg Businessweek, the estimated value of the
pigment industry globally is $30 billion. The value of titanium dioxide – used to enhance the
white brightness of many products – was placed at $13.2 billion per year, while the color Ferrari
red is valued at $300 million each year.
Page 18 of 21
Precautions
1. All apparatuses used for the experiment should be thoroughly
cleaned before use to prevent any unnecessary addition of
impurities.
2. All chemicals used should be accurately measured. If more or less than the
required amount is used, then the pigment may not be formed efficiently.
3. Make sure the right chemicals are used else an unwanted reaction may take
place, which may thus lead to incorrect results.
4. Filtration of the pigment should be done carefully to get maximum amount
of pigment.
Page 19 of 21
Future Scope
1. There is tremendous scope for paint pigments in the future.
2. Increasing experimental methods and newer technologies in
preparation of pigments has increased the quality and
quantity of pigments obtained.
3. Scientists are trying to increase the efficiency of the various paint
pigments by newer experimental methods.
4. New shades of colour have been developed in laboratories.
5. Industries have increased their production of pigments and dyes
through scientific technology.
6. Pigments are now being used more widely.
7. Natural pigments / non – toxic pigments are being synthesized to
avoid any health hazards due to the dangerous chemicals contained
in them.
Page 20 of 21
Bibliography
i. www.wikipedia.com/Pigments
ii. www.google.com
iii. projects.icbse.com
iv. www.odinity.com/synthesis-malachite- verdigris/
v. www.ionicviper.org
vi. www.webexhibits.org
vii. www.compoundchem.com
Page 21 of 21
