81/2/1 ARTISTS CANVASES. A HISTORY Caroline Villers ICOM Committee for Conservation 6th Triennial Meeting Ottawa 1981 of Structural Restoration of Canvas Paintings Working Group:81/2/1-1 ARTISTS CANVASES. A HISTORY Caroline Villers Technology Department Courtauld Institute of Art 20 Portman Square London W1H OBE Great Britain The use of woven textile supports for paintings goes back to Ancient Egypt. In Europe, however, little survives prior to the 15th C. As we shall see this does not in itself argue against an earlier and continuous tradition of use, since it is clear that the vulnerability of the support and perhaps the technique used, account for the failure of these works to survive. The following paper sets out to survey what we do know of the use of textile supports from the evidence available and draws attention to the repeated selection of linen, which remains the favourite support to this day. The traditional use of animal skin glue is considered as a factor in the deterioration of the painting. About 150 years after their widespread adoption textile supports had begun to deteriorate sufficiently for lining to become a routine procedure, and it is not surprising that in selecting a suitable fabric the conservator also tended to prefer linen. Compared to other available natural fibres linen was a jensible choice, however, today many synthetic fibres exhibit super- or chemical and mechanical properties that might make them preferable both as painting supports and lining materials. EARLY PAINTINGS ON CANVAS. HISTORICAL BACKGROUND In Europe fabric begins to dominate over wood as a painting support during the 16th C., but there is ample evidence for the existence of paintings on fabric before that date. The wills and inventories of the citizens of Douai, Tournai and Louvain in the Southern Netherlands indicate that it was slightly more common to own paintings on fabric than on wood in the 15th C. In Italy the Medici Inventories of the 1490s list a surprising number of paintings, large and small, secular and religious, on fabric. In England the records of the Probate Court of Canterbury also indicate the possession of more works on fabric than on wood. 1 The Manuscript of Jean Le Begue, transcribed in France in 1431, contains references to textile supports for painting. A method that81/2/1-2 seens to contain the essentials of a technique that remained pre- valent in Northern Europe for several centuries is described in Eraclius Book IIT, generally assumed to be a 13th C. French document: "If you wish to paint a linen cloth and lay gold upon it pre- pare it thus: Take parchment or clippings of parchment and put them into a jar with water which mist be placed over a fire and made to boil as before directed, then dip a cloth into it, take it out immediately and stretch it onto a wet panel and let it dry. Then burnish or polish it all over with a glass muller and stretch it out fastening it onto a wooden frame with the thread. You may then paint on it with colours distempered with size or gum or egg" (Merrifield, Treatises I, p. 230). 2 The use of a chalk ground is the most common variation. Paint- ings executed in this technique may have been either cheap mass pro- @ duced images, or individual works of high quality, like 'The Entombment of Christ" by Dieric Bouts (National Gallery, London) painted c. 1455. It is painted in an aqueous, probably gum medium on fine linen (20 warp 20 weft approx. per cm) and has a very thin brown, pigmented chalk ground. Perhaps the earliest surviving example is 'Virgin and Child with Angels' by Malouel (Museum Dahlem, Berlin- Dahlem, on loan) painted 1405-10. Malouel was employed at Dijon by the Dukes of Burgundy who also owned paintings on fabric supports that have not survived. In 1387, for instance, the painter Jean Beaumez was paid for two such works, one at least in colour. 3 Other kinds of paintings on fabric include civil and religious banners, a variety of temporary decorations and those outstanding examples, the painted substitutes for tapestries for which Roger van der Weyden was famous. It is interesting that in Bruges there were separate Guilds of Painters and Cloth-painters, and together with the Embroiderers Guild, the Painters were aggressive in trying to limit their spheres of activity. In one instance they tried to prevent the Cloth-painters using an oil medium. Banners were sometimes painted in oil, but in general, it seems reasonable to suggest that paint- ings on panel were executed in oil and those on fabric in watercolour 4, Where it has been possible to check extant 15th C. Netherlandish paintings (Tliichlein) this is the case. Similarly when Pieter Breughel or Diirer painted on cloth they also used aqueous media. Van Mander's Schilderboek 1604 confirms this impression (e.g. Lives of Pieter Koeck, @ Lucas and Marten van Valkenbergh, Hans Bol) and he mentions the existence of 150 workshops at Malines specialising in landscapes, in watercolour, on fabric supports. However, by this time canvas was already predominating over wood and De Mayerne's Manuscript (1620) reflects this change. It is interesting that where artists continue to work on both wood and canvas, as Rubens and Rembrandt did, although consistently painting in oil, their techniques vary considerably with the support: they remain more traditional on wood and freer, more spontaneous on canvas. The obvious implication is that paintings on fabric supports were very common, and yet relative to panel paintings few have survived. The technical innovation is not the use of fabric itself, but that of painting in oil on fabric, which actually occurs in Northern Europe later than in Italy. From the point of view of conservation it may be agreed that the use of aqueous media contributed as much as the fragile nature of the support to the deterioration and disappearance81/2/1-3 of these early paintings. In Italy Cennino Cennini (Thompson pg 103-108) also gives quite long section about painting on various fabrics. There are no in- structions for what we would call independent paintings, but the preparation of a banner sounds familiar. "In the first place stretch it taut on a frame ... go around and around with little tacks to get it stretched out evenly and systematically so that it has every thread perfectly arranged ... take ‘gesso sottile’ and a little starch or a little sugar ... but first put on an all over coat of this size ... and it would not matter if the size were not as strong as for gesso and the less gesso you leave on the better it is; just so you fill up the interstices between the threads". Cennini recommends the same medium, egg, as for panel paintings. A very early example of this technique applied to painting is "The Intercession of Christ and the Virgin" (Cloisters, New York). It is known to have stood on an altar in Florence Cathedral before 1402, and the vertical format and fact that it was only painted on one side preclude the possibility that it was a banner. It is a monumental work, 242.5 x 156.5 cm and made up of several pieces of cloth. It seems that painting on fabric did not become popular in Central Italy as rapidly as it did in the North, so it is particularly striking that the earliest example of a painting in oil on canvas is Florentine: Uccello's "St George and the Dragon" (national Gallery, London) c. 1460. The extraordinary structure of the ground draws attention to the innovatory and perhaps experimental nature of the work. Bromelle has discussed the painting in the context of other Florentine works on canvas and draws attention to the fact that whereas all Uccello's "Battle of San Romano" panel paintings survive other canvas paintings of secular subjects that were with them in the "Camera di Lorenzo" in the Medici Palace in 1492 were descrived as torn and damaged in 1598 and have subsequently disappeared. 5 Eastlake drew attention to the records of paintings in the Veneto in the 14th C. being "executed in the Geruan Manner on cloth", 6 and works by Mantegna from the second half of the 15th C. certainly recall Netherlandish techniques. The earliest securely dated example @:: "St Eufemia" (Galerie Nazionale di Capodimonte, Naples) 1454 catalogued as ‘tempera’. All the examples on fabric in the National Gallery, London are in an aqueous medium or egy tempera and on very fine linen, the finest is "Samson and Delilah" 30 warp 30 weft approx per cm@, The monumental "Triumphs of Caesar" (Hampton Court) are painted in egg tempera on a twill canvas. Vasari also says that both Jacopo and Gentile Bellini frequently painted on fabric, and that Gentile's paintings in the 'Hall of the Great Council' of the Doges Palace were executed on canvas in 1476. One of the earliest surviv~ ing Venetian oil paintings on canvas is Giovanni Bellini's "Madonna and Child with the Doge Barbarigo and Sainte" (Murano, Church of St Peter Martyr) dated 1488. By the time Giorgione and Titian were painting oil on canvas had come to predominate. Vasari noted this development in Venice and suggested entirely practical reasons for it: unlike wood, canvas did not split or harbour worms, it could easily be obtained in the desired sizes and it was light and easy to trans-81/2/1-4 por* (Maclehouse, Vasaripg. 236-7). Certainly the wet and salty atmos- phere of Venice was unsuited to the survival of monumental panel paint- ings or frescoes. Perhaps slightly surprisingly transport does seem to be a major concern and motivation for using canvas. In a letter concerning a commissicn in 1477 Mantegna wrote "I do not understand since your excellency wants them so quickly in what manner they are to be done. In a drawing only or in colour. On a panel or on canvas and what size. If your lordship wants to ship them far away they should be done on thin canvas so they can be wrapped around a little pole". (CG Ibert Italian Art pg. 12). The ease with which a painting could be rolled up also becomes the criterion for a successful size or ground leyer and the Venetian writer Borghini (Il Riposo pg 172, pg 175-6) draws particular attention to the preparation of Netherlandish paintings on fabric which could be easily rolled up and transported without cracking or flaking. In fact the Bouts "Entombment" was once in the Foscari Collection in Italy and possibly may have been part of an altarpiece painted for export. It is debateable how much these practical considerations disguise a more profound change in the nature and function of paintings, but it is, nevertheless, striking that we have no record of purely aesthetic preferences being expressed. The use of coarser weaves and different weave patterns introduced greater textural variety into Venetian paintings. Although the artist must have made a personal selection and sometimes been aware of the novelty of his choice, no record survives and the examination of one artist's canvases, Tintoretto's, failed to reveal any logic or consistency for often his canvases are made up of pieces sewn together with apparent indifference to the surface effects of the location of seams, direction of weave, or patchwork finish. 7 Similar problems can be found in the work of Rubens or Rembrandt. Surveying the Tate Gallery's questionnaires to contemporary artists the expression of practical rather than aesthetic reagons also predominates with regard to supports, and again the balance is difficult to assess. A continued preference for linen canvas, for example, is generally linked to the ability to afford it or the desire to be aligned with tradition, often tradition as defined by handbooks like Doerner's, artists suppliers or the market. This often contrasts with attitudes expressed towards paint media or pig- ments or other items incorporated into a painting. € SIZE Obviously deterioration problems cannot be attributed to the textile support alone, since the behaviour and survival of the support will also be influenced by the treatment it receives before painting. The traditional practice of pumiceing to remove knots and loose threads weakens a canvas stretcher design and the stretching process must be called into question and Marion Mecklenberg has pointed out 8 that, among other causes of problems, it would appear that one of the most active layers in the painting composite is the glue size layer. He suggests that dessication can lead to very large stresses in the size film which can lead to fracture in the paint and ground layers. Linen and cotton are traditionally associated with the use of size. Not only are they frequently sized by the artist, but they are often sized at least on the warp threads during weaving. Typical aqueous81/2/1-5 responsive sizes used include locust bean size, starch sizes like Farina (potatoe starch size), sage flour size. Cotton yarn is customarily more heavily sized than linen yarn. One manufacturer supplied the information that in 16 oz linen approximately 3% of the weight of the fabric is accounted for by size. Synthetic based sizes are also used. Historically some of the problems posed by the use of size were taken account of by writers on painting techniques. Various types of size were available, but there was a general preference, clearly ex- pressed from the 17th century on, for one made from young pigs skin, kid or glove cuttings, because it remained soft and flexible whereas parchment size "being strong and harsh causes a certain shrinking of the canvas which has a bad effect" (Volpato, Merrifield II pg. 728. iso Symonds, Beal pg. 86; Pacheco Bk III, ch V, pg 71; Palomino fol II Bk V pg. 484; Felibien ch V pg 295; De Mayerne, Van de Graaf No 9 pg 139). De Mayerne implies there was some controversy over this, his own experiments favoured kid or young goat skin size "in which all the skill consists, because if the size is tuo strong the canvas cracks and breaks easily; Van Somer however, used "strong size"/ "colle forte" and Van Dyck strong Fish Glue. Both unsuccessfully it seems (Van de Graaf No 15 pg. 140; No 8 pg. 139). Additions of honey which were common in English recipes from 1648-1748 (all based on Salmon's Polygraphice pg. 161) would have created different problems and again De Mayerne records the practice (Van de Graaf No 4 and No 7 pg. 138) while pointing out that the canvas then absorbed so much moisture it became too slack and the paint blanched. Having selected the correct type of size it was also thought important not to apply either too much or too concentrated a solution: "let it (the size) neither be too weak nor too strong; for if too weak it will not defend the canvas from the oil and if too strong it will cause the colour to crack. That which is of the proper consistency will be soft like jelly when it is cooled" (Volpato, Merrifield II pg. 728. Also Symonds, Beal pg. 86; Palomino Vol II ch IV pg. 484). not surprisingly Northern writers are more concerned with the size swelling than with it becoming too brittle, thus causing crack- ing and cleavage, but both fairly consistently recommend the Q@epriication of only oneor two coats of soft weak size. Of course there are exceptions. Writing in Venice in 1578 Armenini recommended entirely saturating the canvas in size applied from the back as well as the front (Armenini, Bk II ch vIII pg. 171). Occasionally there are recommendations to omit the size altogether (Pacheco Bk III ch V pg. 172), although more often commercial primers are blamed for doing this and so causing paint to dry matt (De Mayerne, Van de Graaf No 6 pg. 138; Symonds, Beal pg. 86). Commercially primed canvases begin to predominate from the end of the 17th C. and traditional practice to the present day remains the application of size followed by an oil ground. To avoid some of the problems associated with size in the 18th century Dossie recomm- ended immersing the entire canvas in hot drying oil (Dossie pg. 203). A less drastic solution was the use of Viscose, proposed in 1901 by Church, Professor of Chemistry at the Royal Acadeny, and then by a Committee of the Academy in 1928,9 it wasin fact taken up by Winsor81/2/1-6 and Newton who produced a canvas sized and primed with Viscose called ‘Kcyac', which had the reputed advantages of being resistant to ‘destruction by moisture' and preventing 'tightenings and saggings observable in strained canvases during changes in atmospheric con- Gitions and that a fertile cause of cracking may be removed by th adoption of this treatment’ (1934 Catalogue). Ultimately 'Royac’ failed due to lack of response among artists. Currently synthetic polymer emulsions are being widely used especially for canvases with acrylic grounds. Two reasons are commonly cited for the sizing of canvas by artiste. One is thet it ie necessary to prevent cellulosic materials from coming into contact with oil paint. This need is of course specific to cotton and linen fabric, although it is worth noting that there is very little evidence available to quantify the effects of such contact. The other is that the ground layer needs to be pre- vented from penetrating through to the back of the canvas. This problem continues to exist with modern alternative fabrics and emphasises that not only would a material that does not require siz- ing with animal glue be required, but that this must be related to suggestions as to the most suitable types of ground. THE CHOICE OF TEXTILE During the 16th century Venetian Artists might have chosen from linen, hemp, fustians, silks, fine woolens to paint on. Cotton was briefly manufactured in Spain from 14th-15th C. and in fact a factory was set up near Venice at the end of the 14th C., although it never flourished. So the apparently consistent choice of linen is as not- able then as its continued selection by contemporary artists is now. Undoubtedly flax was the most important vegetable textile fibre in domestic use. Hemp, another bast fibre, may be spun and woven on the same machinery and its production was well established in Italy in the 15th century, large quantities were in fact required to equip the Venetian fleet, but so far only one Venetian canvas Tintoretto's "Last Judgement" (Venice,Church of Madonna dell'Orto), has been cautiously identified as hemp 7. Improved forensic analysis made it possible to identify the canvas of Poussin's "Worship of the Golden Calf” (National Gallery, London) as positively hemp and it seems to have been more widely used in France and Italy during the 17th century. In 19th century French writers quite frequently recommended hemp over linen because of its superior strength (Bouvier ch XXX pg. 508), but its use has not been identified yet. Anthea Callen has pointed out that Paillot de Montabert (1829) while fundamentally opposed to the use of any textile support at all, still expressed approval for hemp. However, she found only one 19th C. catalogue, G Sennelier's, listing it for sale as a prepared artists canvas and that in 1894 10. When 19th century French artists wanted to choose a coarser fabric they seem to have selected ones woven from jute (Hessian, Burlap). Jute was introduced into Europe about 1795, but modific- ations were required to flax spinning and weaving machinery to deal with its harsh fibres, so that it did not become widely available until its production was mechanised in Britain during the 1830s. By 1855 machinery was being exported from Dundee to India where the81/2/1-7 fibre originated. By 1888 Van Gogh was already experimenting with Burlap followed by Gauguin who continued to use it in Tahiti as a matter of choice. It was first sold in Britain as a prepared artists canvas by Rowney and Co in 1913, Quality 'H' (not named until 1926), as a ‘coarse rough cheap canvas for sketching purposes and for Art Students painting in a broad style'; the current catalogue con- tains the sensible warning that ‘Jute has a limited life and this canvas can only be recommended where price is the prime consideration and the life of the painting is immaterial'. Winsor and Newton in- troduced Jute canvas between 1920-25, but had ceased to market it by 1948, and their catalogue also carried the warning that it was ‘not recommended for permanent work’. It remains widely available. Jute mixtures have also been sold, in 1936 for example, Rowney introduced one. 'M', a Flax/Jute mixture. Doerner had already expressed pproval for this combination in 1921 11, although he rejected Hemp/Jute mixtures. In the Guggenheim Museum, New York, there are examples of Burlap being used by Leger, Ernst and Klee in the 1910s and it is striking that several had already been lined by 1953/4, only 40 years after they had been painted. Léger's ‘Contrast of Forms', 1913, was lined in 1953. Jute is an example of an extremely poor fibre being selected by artists quite rapidly after its mech- anised production had begun, and its marketing by Artists Suppliers following afterwards. Another bast fibre, Ramie, has the opposite history. It was recommended by a Committee of the Royal Academy in 1928 9, because of its superior fibre strength as a textile for artists canvases, but inspite of some enthusiasm in the 1930s it was never widely manufactured, was not sold by Artists Suppliers andhas not been used by artists since. Rapid experimentation with Jute contrasts with the history of cotton canvases, which have only become widely used for their intrin- sic properties approximately 150 years after their introduction. As cotton is so widely used today, it is worth briefly surveying its history. In Burope developments in spinning and weaving techniques progressed minimally between 14th-18th C. and these techniques, suited to dealing with long bast fibres, were entirely unsuited to raw cotton. Cotton was imported in large quantities via Venice, but the dystaff and spindle that continued to be used for spinning it, could ot produce a cotton yarn combining strength with fineness. It could only be used as a weft yarn in fustians. However, the arrival of vast imports of cheap cotton from America and the West Indies en- couraged inventions, and all the new machines that were invented were specifically designed for cotton rather than flax. The most import- ant of these were Hargreave's Spinning Jenny and Arkwright's water- frame spinning machine both patented in 1769. Crompton's Mule also developed at this time, was better suited to spinning warp as well as weft yarns. Significant developments in the weaving process were Kay's ‘Flying Shuttle’ patented in 1738, and Cartwright's Power Looms, patented 1786-8, which enabled the entire process to be industrialised in factories. In 1790s Ginning machines were intro- duced in America for mechanically removing the cotton heads from the plant. 12 The mechanisation of flax spinning and weaving lagged about 50 years behind cotton. Shortages imposed by the American Civil War en-81/2/1-8 couraged experiments and finally led to the design of the flax spinning machine patented by Kendrew and Porthouse in 1787. Kay's Flying Shuttle was introduced into Ireland for use in flax weaving in 1776, but thirty years later in 1807-9 premiums were still being offered for its use. It was only between 1839-54 that the most successful power looms for flax weaving were developed in Britain 13. It is reasonable to assume that from this date machine woven linen canvases began to be sold. Wehlte states that the French firm of Lefranc gave 1867 as the year in which they began to sell machine woven prepared linen canvas and theGerman firm of A Schutzmann 1844, 14, Between 1840-1900 Winsor and Newton catalogues exemplify the steady expansion of the variety of available weave types and weights. After the 2nd World War the selection was reduced to only four types and for 10 years the best quality ‘Winton’ was unavailable. Despite wartime restrictions, strenuous efforts were made to maintain the sale of linen canvases. Inspite of the early mechanisation of cotton spinn- ing and weaving processes it was slow to gain support as an artists canvas. At the beginning of the 19th C. Bouvier (ch XXX pg. 508) re- jected it as too weak and an examination of French Colourmens cata- logues by Anthea Callen has shown that the first named reference to prepared cotton canvases 'Nadapolam Toile’ was in 1855 by Lefranc and Cie., when it was prepared for pastel drawings only and cost 2 france less per metre than linen. The earliest mention of its sale specif- ically for oil painting is in 1894 in G Sennelier's Catalogue and 1896 in Lefranc's catalogue although there is insufficient evidence for this to be taken as the precise date of its introduction. Winsor and Newton supplied the information that cotton was introduced into their range of prepared artists canvases between 1900-06. The 1906 Catalogue lists a ‘School of Art Canvas' as a 'good serviceable cloth of English manufacture’ and in 1928 it is specifically admitted to be cotton. It was sold in 6 yd rolls up to 74" wide and the price for the 74" width was 21/- per roll compared with 54/- for the best linen. This approximate ratio seems to be the price differential to the present day. Cheapness would seem to have been the main reason for its introduction for use either as a student's or sketching canvas and in general artists today still seem to use cottou until they can afford linen. In 1907 Rowney and Co offered a ‘Students Canvas’ that was des- cribed as follows: "This canvas is made of half flax and half cotton and has the advantage over all cotton canvas being stronger and not so easily dented". In 1936 two types were available, an openly woven canvas with a cotton warp and flax weft (Qualtity 'S') and a closely woven canvas with a flax warp and cotton weft (Quality 'V'). Winsor and Newton also introduced a mixed cotton/flex canvas in 1935 (NP Range) specifically prepared"to meet the requirements of students in Art Schools where it is not necessary for imperfections in the raw cloth to be removed by picking before it is prepared". It may have been their closer resemblance to linen that gave these cotton/ flex mixtures their appeal. Chemically and mechanically they were not an improvement, and Doerner does in fact warn against them. It is entirely probable that these cotton/linen mixtures may have been used much earlier and more widely than we think especially if we con-81/2/1-9 sider the history of the textile industry and its probable influence. Between 1890-1910, there was a vast expansion in both britain anduFrance,, in the variety of. prepared: canvases being sold. It was during this time that cotton Canvases became widely available, a century after cotton production had become mechanised. It was sold then asa cheap substitute for linen, and it took another 40 years ~ for artiets to-begin to upe it.as a-fabric with ite own intrinsic properties; by which time they generally: chose cotton ducks and often the heavier weights. The earliest painting in the Tate Gallery, London’ on'eotton. duck,is-Conroy: Maddox"s"Paseage de.l!Operal’, 1940, The next’ is Jacksom Pollock's "Yeldow’Islahds", 1952. Our impresaion is that while cotton duck was unusual in the 1940s, by the 1950s it was becoming commonplace, especially in America. The usual reasons given for ite adoption are the large available widths, its whiteness, absorbency and cost. Although Winsor and Newton listed three qual- ities of linen available in 126" widths before the war, they were not available afterwards. Whiteness and absorbency were obviously crucial to the ‘stain’ paintings of Morris Louis and Helen Franken- thaler who began using thinned oil paint on unsized, unprimed cotton duck. Frankenthaler's "Mountains and Sea" (Metropolitan Museum, New York, on ldan), 1952 is a seminal example. The previous year she had been painting on unsized, unprimed linen. A wide variety of other textiles have obviously been used from time to time. Robert Rauschenberg's "Hoarfrost" series employ silk, satin and muslin. The use of silk hasalong tradition, at least one example survives from the 14th C. (Parement of Narbonne, Louvre, Paris) as well as works by the 17th C painter Guido Reni. In the 1940s Clyfford Still painted on brown and blue denim, a support which seems as unstable as the blue or black cloths collaged with white that Cennino Cennini describes for wall hangings. Medieval artists also painted clothing, so they would have known how to work on wool or velvet. Velvet continues to be a favourite support for colourful tourist clichés. It emphasises the fact that while almost every fab- ric has been tried, few of them are entirely new. Those that are new have not been extensively tried yet. If one considers how thoroughly synthetics have replaced natural fabrics in the clothing industry, artists suppliers and artists appear very conservative in this res- pect. Among the Artists Suppliers known to us Lefranc and Bourgeois (France) are exceptional in marketing a prepared (acrylic ground) polyester non woven ‘Polytoile' 15, and Ploton's (London, England) in selling rolle of prepared (acrylic ground) Nylon canvas as well as an unspecified Italian synthetic textile. Linen and cotton have thus continued to be preferred by artists seeking to paint on stretched fabrics. Given the materials previous- ly ayailable, linen in particular has always been a sensible choice, yet today from the viewpoints of their chemical stability and mech- anical properties they are very far from ideal, materials. It is worth considering some of their drawbacks in more detail since this will help to serve as one reference point in assessing new materials. Strength loss is the most evident problem. Whilst linen and cotton begin their life with much greater strength than is necessary for a painting support, they retain it only for a short period. The cellulose chains of which they are composed suffer degradation lead-81/2/1-10 ing to chain scission under the influence of light, moisture and en- vironmental pollutants. The strength loss is rapid and extensive. Tests conducted on samples naturally aged in the Tate Gallery, London revealed that in only 24 years linen canvas samples had de- clined to practically 1/3 of their original strength 16. Hardly sur- prising then that so few canvas paintings survive more than a couple of hundred years without some form of treatment to provide additional structural support. Unlined paintings of more than 300 years of ege are so rare as to be almost collectors items. Some of this exten- sive treatment must of course be attributed to lining having becone a standard restoration treatment, though it should be remembered that this is not without a certain basis in the condition of the paintings themselves. It is evident that a large’ number of 20th century paint- ings have already been lined after perhaps only 50 years of existence. Such treatments are themselves hazardous operations and tend to im pose significant changes on’ the appearance and handling properties of the painting, especially if considered as a whole object rather than simply the visual image. Cotton is even less satisfactory than linen. The fibres are 2 to 3 times weaker than equivalent linen fibres and consequently though their rate of deterioration due to light is slower than that of linen 17, low strength values will quickly be reached. These factors are sure to cause immense problems for conservators; fifty years from now entrusted with the care of the large paintinge on cotton which are so common in our galleries today. Just as problematical given the optical role that exposed can- vas plays in many modern paintings are the colour changes that accompany the chemical degradation. Significant darkening and yellow- ing of the surface take place very rapidly. The 24 year old linen samples from the Tate Gallery showed a decrease in reflectance of 10% at the red end of the spectrum and 50% at the blue end of the epectrum 16. Again cotton is known to change colour more rapidly than linen and since its natural cream white colour has often been utilised by artists such a change will completely alter the tonal relationships within the painting. The original intention of an artist such as Morris Louis or Helen Frankenthaler will be irretrievably lost. But more subtle problems also exist. Linen and cotton are moisture sensitive supports. The moisture regain at 65% RH of linen and cotton is taken as 12% and 8.5% respectively. They swell and shrink differentially from other layers in the painting and their mechanical properties also change. This process in the painting as @ whole can lead to powerful shear and tensile etresses being set up and to cracking and delamination. Cotton can imbibe as much ae 40% moisture at 100% RH andappears to respond more rapidly to mois- ture changes. It has been observed that large paintings on cotton are particularly prone to fluctuations between very slack and very taut states. This affinity for moisture also leads to soiling of the cotton and linen supports. Woven fabrics in general and cotton and linen in particular do not have ideal mechanical properties when considered for use as a painting support. What is required is a material which becomes taut under the minimum of applied strain, which does not ‘subsequently re-81/2/1-11 lax and which has the same properties in all directions. This re- quires a material of high initial Youngs Modulus (and low elongation) resistent to stress relaxation and creep and exhibiting isotropic behaviour. Cotton and linen fail on all these counts when consid- ered in the woven form. These problems are increased when the whole stretching process is considered. Given this well established catalogue of drawbacks it is per- haps surprising that more attention has not been paid to developing new painting supports. Among the reasons for this may be the facts that conservators have not played a prominent role in developing artiste materials, and that most artists suppliers are primarily manufacturers of paint, who only act as retailers for canvas that is purchased from other specialised suppliers, whose reputation reste on the traditional excellence of their product. So, it is an area @:: research and development in which conservators have a special role to play, not only in their capacity to offer advice but because the criteria for the most durable and stable painting support are the same as those for the most durable and stable lining canvas. NOTES: 4. L CAMPBELL "The Art Market in the Southern Netherlands in the 45th Century", Burlington Magazine, 1976, CXVIII, p 188-198 J SHEARMAN "The Collections of the Younger branch of the Medici", Burlington Magazine 1975, CXVII, p 12-27 PRIVATE COMMUNICATION, Susan FOISTER, June 1980. Information to be published inthe Burlington Marazine. . Information from documentary sources are followed by an abbreviated reference. The following texts will be referred to: G B ARMENINI De veri precetti della Pittura ed. S Ticozzi 1820 (published 1586) M BEAL A study of Richard Symonds. His Italian Notebooks and their relevance to 17th century painting techniques (1649-51) PhD, Courtauld Institute, 1978 R BORGHINI Il Riposo, Florence 1584 P L BOUVIER Manuel des jeunes artistes et amateurs en peinture, e 2nd ed. 1832 (published 1827) CENNINO CENNINI Il libro dell'Arte ed. D V Thompson 1933, reprinted 1954 R DOSSIE The Handmaid to the Arts, 2 vols, 1716 A FELIBIEN Des principes de l'architecture, de la sculpture, de la peinture et des autres arts qui en dépendent, 1966. 3rd ed. Paris 1699 (published 1676) J A van de GRAAF Het de mayerne Manuscript als bron voor de schildertechniek van de Barok, 1958. (Manuscript 1620) L S MACLEZHOUSE Vasari on Technique 1907, reprinted 1970 (Vasari published 1550, 1568) M P MERRIFIHLD Original Treatises on the Arts of Paintiug, 2 vols Reprinted 1967 (published 1849) F PACHECO Arte de la Pintura ed. F J Sanchez Canton, 2 vols. 1956. (published 1638) ‘A PALOMINO Bl Museo Pitorico, 1947. (Published 1724) W SALMON Polygraphice, 8th ed. 1701. (Published 1672)81/2/1-12 M KIRBY TALLEY Portrait Painting in England. Studies in technical literature before 1700. PhD, Courtauld Institute, 1978 C. VILLERS Discussion of evidence Part 1:3 The Early Flemish Medium. Final Year Thesis, Technology Department, Courtauld Institute, 1976 J VAN DE GRAAF op. cit. p 13ff N BROMELLE, ST George and the Dragon, Museums Journal, 1959, vol 59, p 87-95 Sir Charles Lock SASTLAKE Materials for a History of Oil Painting, Reprinted 1960. p 90 (published 1847) J PLESTERS AND LAZZARINI “Preliminary Observations on the technique and materials of Tintoretto", Conservation and Rest- oration of Pictorial Art, Lisbon Congress 1972, ed N Bromelle and P Smith, 1976, p 7-26, p 12 J PLESTERS "Tintoretto'’s Paintings in the National Gallery", National Gallery Technical Bulletin, Vol 3, 1979, p 3-24 M MECKLENBERG Materials, Environments and Artists: Questions of Compatibility. 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