Resins-based mediums are those made with resin dissolved in a solvent, such as dammar spirit varnish (dammar or damar in turpentine), mastic spirit varnish (mastic gum dissolved in turpentine), or megilp (oil and resin-based medium and later Maroger mediums). Resin-based mediums and varnishes have become popular additions to oil paint since the nineteenth century.
Aside from picture varnishes, the primary use of resins in oil paintings was in glazes. The use of resinous mediums in oil paint is certainly not new. Researchers have found natural resins, such as mastic and, more commonly, those from pine trees, in the earliest European oil paintings of the fifteenth century. However, using natural resins in oil paint was confined to specific passages of paintings. It was not until the latter half of the eighteenth century do we find paint films incorporating resins throughout paintings.
In the right-hand kneeling figure's green cloak of Girolamo da Carpi's The Adoration of the Kings, we see an early use of resin in oil paint. The paint contained walnut oil with a small amount of pine resin. Examination of a painting fragment showed that it was a part of the paint medium, but the resin was used in one or two isolated areas. It appears that Carpi added resin for specific effects, rather much as Armenini described for painting and glazing green draperies.
Early use of pine resin in oil paint as a medium for glazing.
Girolamo da Carpi, The Adoration of the Kings, c. 1545–50, oil on wood, 44.2 x 32.1 cm, National Gallery, London
Defects usually accompanied the use of resins in oil paintings in the paint film. When defects are often observed, they are not necessarily the result of the resin but the painting technique used in its application. This is indicated by the reticulated paint surface of the green cloak because less reticulated areas of the paint contained somewhat less pine resin. This suggests that the painter stirred a proportion of pine resin varnish, ‘vernice commune,’ into the green paint, a little generously and carelessly perhaps. This haphazard application method often results in uneven drying, which often leads to drying cracks and wrinkling.
A few seventeenth-century artists were habitually adding a small amount of pine resin to their paint, either for particular colors or to add increased gloss and transparency to the paint. This practice effectively gives increased depth to areas of shadow or glazing, and it is not uncommon to find the addition of resin to the paint for this purpose. Philippe de Champaigne added small amounts of pine resin to linseed oil used for the glaze of Cardinal Richelieu's red robe. In contrast, pine resin and mastic were present in the medium used in the glaze on the sitter's coat in a portrait attributed to Gabriel Revel.
The artist added small amounts of pine resin to the linseed oil used for the glaze of the red robe.
Philippe de Champaigne (1602–1674), Cardinal de Richelieu (1633–40), oil on canvas, 259.5 x 178.5 cm, National Gallery, London
The artist added small amounts of mastic and pine resin to the linseed oil used for the glaze of the robe.
Gabriel Revel (1643–1712), Portrait of an Astronomer (c. 1670), oil on canvas, 110.9 × 95.3 cm, National Gallery, London
Resins in Oil Painting—Search for the Perfect Megilp
The use of resins mixed with oil paint did not get its impetus until the latter half of the eighteenth century. A preparation of linseed oil cooked with lead and mastic spirit varnish became quite common then. This medium was known as megilp. As early as 1768, William Donaldson wrote about this medium in The Life and Adventures of Sir Bartholomew Sapskull: 'The magilp was a nostrum known only to the ancients; but our modern artists..have labour'd..to find out this valuable mystery, and as they say with some degree of success... The magilp produces that warmth and serenity which characterizes the peculiar merit of Claude Lorraine.' Many painters at this time believed that certain "secrets" had been lost, and if the secrets were rediscovered, it would be easier for modern painters to achieve the same effects as the Old Masters. The search for these secrets became so pervasive that it attracted ridicule among artists in Britain and its colonies. The president of the Royal Society of Arts at that time, Benjamin West, trusted in a fraudulent claim of the discovery of the "Venetian Secret" that put his reputation at serious risk. Another artist, James Barry, writing in the 1760s, poked fun at 'such people of ours who are floating about after Magilphs and mysteries.'
Many believed that Titian and other early artists had used such mediums, but the recipe had been lost over the centuries. The search for the perfect medium would turn out to be an important part of the history of painting techniques in the second half of the eighteenth century and throughout the nineteenth century as well.
An entry dating from 1767 records the materials used by Joshua Reynolds for specific paintings and reads 'Miss Cholmondley con olio e Vernicio di cera. poi / verniciulo con yeos (?) lake e magilp.' Similarly in the same year the next entry is as follows 'Lord Townsend. prima con macgp. poi Olio. poi Mag. / Senza olio. Lacca. poi Verniciata con Virmilion.' This is one of the first written occurrences of this medium. The obscure origin of the word megilp seems to be reflected in the many variations in its spelling; by 1854, a total of twenty-three different versions had been listed in Fairholt's Dictionary of Terms in Art.
Megilp is a thixotropic gel consisting of two-component materials whose properties vary significantly as the proportion of the oil and resin changes. It typically consists of mastic gum dissolved in spirits of gum turpentine (mastic varnish) and sugar of lead (lead acetate) or litharge (lead oxide) cooked in linseed or walnut oil (also called "black oil"). The mastic resin and oil vary in proportions from 3:1 to 1:3. Its film-forming capability, the tendency of megilp to segregate afterward, tackiness, and ability to absorb more or less dust than dried linseed oil paint all depend on the exact proportions. Reynolds apparently used a variety of formulations and proportions of megilp in his work, which has led to variations of yellowing and solubility in his paintings and made them very sensitive to cleaning.
The portrait of Lord Heathfield suffered greatly from the effects of Reynold's painting techniques and poor use of resins.
Joshua Reynolds (1723-1792), Lord Heathfield of Gibraltar, 1787, oil on canvas, 142 x 113.5 cm (55.9 x 44.7 in.), National Gallery, London
The portrait of Lord Heathfield, so much admired in its day, has unfortunately suffered from the irreversible effects of Reynold's particular painting techniques. M. Constant de Massoul, whose treatise on the art of painting was published in London in 1797, only ten years after the picture was painted, cautions against such methods.
'Many painters both in Glazing and in Painting, make use of varnish mixed with fat oil, because then the Picture appears brilliant and not imbibed†.
This method, so pleasing, and therefore so seducing in practice, may, without doubt, be useful; but then it ought to be used with some precaution. To this may be attributed the change that the Pictures of the celebrated Sir Joshua Reynolds have undergone. ...You may have the more to dread, as Pictures being varnished only in some particular places, they may crack in all those parts, where there is an union of colours with varnish, and those simply with oil.
† Imbibed, is a term in Painting: it is the effect that oil produces upon a canvass, that has not been long painted. It soaks into those colours that are underneath, and causes the upper ones to appear sunk. But white of egg or varnish makes them come out, and appear as when first painted.'
It is clear that Reynold's use of a medium that contained a varnish was responsible for the severe cracking in many of his pictures. One of Reynold's pupils, James Northcote, wrote about Reynold's technique in a letter to his brother dated August 23, 1771:
'He uses his colours with varnishes of his own because the oils give the colours a dirty-yellowness in time, but this method of his has an inconvenience full as bad, which is that his pictures crack; sometimes before he has got them out of his hands.'
Northcote also remarked that 'it is common with painters in London to use mastic varnish with their colours.'
J.M.W. Turner's The Fighting Temeraire tugged to her last berth to be broken up, 1838 had never been cleaned before the National Gallery's ‘Making and Meaning’ exhibition in 1995. An examination before cleaning showed that Turner used different resins throughout this painting, typical of much of his work.
Turner often used pine resin and mastic gum in the form of megilp in his work.
Joseph Mallord William Turner (1775–1851), The Fighting Temeraire tugged to her last berth to be broken up, 1838, 1839, oil on canvas, 90.7 x 121.6 cm, National Gallery, London.
Turner used walnut oil, sometimes heat-bodied, as his principal medium, but analysis of this painting shows a range of resins mixed with the oil in different areas of the painting: pine resin and mastic in the brownish-black shadow of the buoy, pine resin, and dammar in the mustard-colored reflection of the sun in the sea; an unidentified resin in the white impasto of a cloud. These probably indicate the use of the various varnishes, megilp, and other proprietary products, in which Turner showed great interest and is also known to have purchased, mixed into the paint on the palette.
Megilp can be made from linseed oil cooked with sugar of lead or litharge and then mixed with mastic spirit varnish. These megilps subsequently show different behavior in aging, and Turner's megilp appears closer to the sugar of lead type of megilp. Documentary evidence indicates that Turner used sugar of lead in copious amounts in his paintings. However, megilp of the litharge type has also been found in his paintings, such as The Dawn of Christianity, and in the works of many other artists of the nineteenth century.
While megilp introduced a pleasing smoothness of application to the paints it was mixed with, it also caused numerous problems: darkening, cracking, and a general weakening of paint films. These problems were noticed even in the nineteenth century, but manufacturers continued to supply it because many painters liked it; even more remarkable, megilp is still available today as the reincarnated Maroger's medium.
Resin-Based Megilp Reincarnate: Maroger's Medium
The painter Jacques Maroger, who was Technical Director of the Louvre Laboratories and President of the Society of Restorers of France in the first half of the twentieth century, believed that megilp, or variations of the medium, was used by Old Master painters as early as the mid-fifteenth century.
According to Maroger, he had discovered the secret of Van Eyck, Rubens, and other painters, which had allegedly been lost since the death of Rubens. The earliest recipes involved mixtures of dammar varnish, oil, and gum arabic; the oily and aqueous components were mixed vigorously until they made an emulsion that became viscous like mayonnaise upon standing. Another secret element was what Maroger called "black oil," which consisted of linseed oil cooked with 10 percent of its weight of litharge until it turned black. However, written correspondence with several other artists, Reginald Marsh and John Steuart Curry, shows that Maroger's techniques were constantly evolving. Curry soon began to express doubts about the secrets of the masters and asked Marsh if there was any written corroboration of Maroger's theories. Marsh could not give him any, so Curry made inquiries elsewhere and turned to Frederick Weber of F. Weber and Company for his opinion of Maroger's materials. Weber warned Curry that the litharge in the black oil would make it tend toward more yellowing.
By 1948, when Maroger published his book The Secret Formulas and Techniques of the Masters, he had developed many additional recipes that purportedly allowed one to paint like masters of various schools and periods. Egg yolk is added in some recipes, and beeswax is an ingredient in many others, especially in the recipes of Italian painters. Many unsubstantiated claims are made, such as the statement that the Dutch "Little Masters" did not use wax but Rembrandt used 'the maximum quantity of wax'. Among the formulas in his book, Maroger describes resin-based mediums and provides recipes for making them.
Some argue today that Maroger's mediums are different from megilps. John Bannon points to a passage in Maroger's book (page 100) where he condemns megilps. Megilps differ very essentially from Maroger's mediums because the oil and lead are not boiled. The formulas derived by Maroger from ancient manuscripts and lab trials call for cooking the oil with litharge (lead monoxide) until the oil becomes polymerized.' However, upon closely examining literature from the eighteenth and nineteenth centuries, it becomes clear that many recipes for megilp existed. It was described by Nathaniel Whittock as 'a compound of various ingredients mixed to the consistence of a thick treacle,' which is why in German it was known as Malbutter, literally "paint butter."
Of the numerous recipes given for megilp, they essentially differed in two basic ways; one in which sugar of lead (lead acetate) was added to linseed or walnut oil as a dryer without heating, and another litharge was cooked in the oil. The latter recipe is essentially that described by Maroger in his book. Maroger mediums are reformulations of megilp that were popularized in the latter half of the eighteenth century by such influential artists as Reynolds and Turner.
Ralph Mayer criticized Maroger for his recipe of black oil and mastic spirit varnish in a review of Maroger's book in the Magazine of Arts. He later wrote in The Painter's Craft, "History teaches us that the wisest course is to adhere to the simple oil-paint technique as much as possible, to use oleoresinous painting mediums with restraint, and to avoid complex jelly mediums." Although not a jelly medium, Mayer writing in his book, The Artist's Handbook, instructs artists to use a complex mixture of equal parts dammar varnish, bodied linseed oil, and turpentine in their painting.
Artists who use Maroger's mediums in their paintings claim that the litharge cooked in linseed oil 'prevents mediums from discoloring and other forms of degradation.' They also claim laboratory tests show that the paint film incorporating Maroger medium is 'virtually indestructible,' further pointing to their work and the works of 'thousands of students, amateurs, and artists that are now fifty or more years old 'show no signs of deteriorating'. Of course, fifty years is not a long time in the life of painting. Whether one accepts these claims or not, an important consideration that appears to have been overlooked by most is the solubility of the dried paint film and what happens during varnishing and cleaning paintings.
The Solubility of Resins is an Important Consideration
For centuries it has been common practice for artists or someone else to apply a coating of varnish to paintings. Before the introduction of modern synthetic materials, the traditional materials used were among the natural resins available at the time. Such varnishes became darker, yellow, and obscure within a few decades of application. It has been common practice to clean paintings at intervals, removing the darkened and obscuring varnish and possibly dirt or other substances accumulated on the painting. The cleaned painting would usually be re-varnished by the restorer, using materials available at that time, which might suffer similar changes in appearance. Cycles of cleaning and varnishing occur repeatedly during the life of a painting; reducing such cycles has been the motive behind developing stable, reversible varnishes. Even if a varnished painting requires a simple re-varnishing without the need for the varnish to be removed, a good practice generally involves surface cleaning to remove any grime and dirt accumulated on the varnish layer. The restorer must be prepared to encounter not just a single homogenous layer of natural resins or synthetic polymers or resins in the picture varnish but very complex structures in the original painting that may also include resins used in the picture varnish.
Throughout the history of oil painting, there were principally two types of picture varnishes: resin-oil and spirit varnish. The resins used in spirit varnishes can only be removed by the dissolving action of organic solvents. Removability does not depend on the complete dissolution of the varnish; the solvent need only to change the physical properties of the varnish to such a degree, by swelling or softening, that the varnish can be removed by rolling or wiping a swab on the surface. The solvents typically used to apply a spirit varnish (mineral spirits or spirits of turpentine) are largely benign to an oil painting so that the varnish can be applied without adverse effects on the paint. However, as resins age, their solubility also changes, so different solvents must be used to remove the varnish. The solvents necessary to dissolve or swell an aged varnish layer may not be friendly to the original painting and may cause the paint to swell, soften and loosen during cleaning. Their effect may be sufficient that they cannot be used to remove the varnish without harm to the painting.
Cleaning a painting provides both risks and benefits that must be carefully considered. The task in cleaning then is to use solvents to remove the varnish but not damage the surface of the painting. The primary concern is that the paint might be removed during cleaning. Another risk that has received considerable attention lately by conservation is 'leaching,' the potential for soluble compounds in the paint to be extracted during cleaning. The loss of these components has been linked to the embrittlement of the paint film. A third concern is what may be left behind during cleaning. Some cleaning materials incorporate surfactants or other ingredients that do not evaporate but may remain on the surface. These must be carefully removed; otherwise, they could have an adverse effect on the paint film.
Different types of paint film differ in their solubility and extractables*
Careful consideration during cleaning is given to the composition of the painting and the picture varnish. The solubility of these materials is investigated, and solvents are chosen based on their solubility characteristics. The task of restorers is to remove the old varnish without attacking the underlying original painting. Hansen solubility parameters have been used since the late 1960s to select solvents to remove varnishes. A special technique used frequently by those who restore paintings is to plot the relative solubility parameters of the picture varnish and the underlying paint film, in the case of many old paintings, dried linseed oil, on a two-dimensional graph, known as a Teas Graph or plot.
Hansen Solubility Parameters
|Dried Linseed Oil Paint||16.0||6.0||7.0||5.0||1.000||9/22|
|Dammar Gum, Dewaxed||18.4||4.2||7.8||8.3||0.915||30/56|
The solubility characteristics of freshly applied dammar and mastic can be visualized on a Teas plot. Because dammar and mastic resins are composed of various compounds, not all components will be dissolved by any given solvent. For this reason, their solubility is plotted as regions of varying areas on the graph.
Figure 1. Teas plot for the estimated solubility of mastic, dammar, and dried linseed oil paint.
Different batches of natural resins, such as dammar and mastic, may have different solubility parameters. Dammar and mastic are resins collected from trees so the constituent components vary. If a commercially-prepared dammar or mastic varnish is used, additives may change its solubility and complicate removal. If a dammar or mastic varnish has been stored for some period, this could also affect its solubility. Even if the varnish is freshly prepared but with turpentine that had been stored for a long time, this too could affect the solubility of the varnish. The types of paints used, the addition of mediums and the amount of time that passed before the painting was varnished—all play into the ease or difficulty of removing a varnish.
Figure 2. Teas plot for the estimated change in the solubility of mastic as a function of light aging.
As resins age, their solubility characteristics likewise change so that the original solvent used to dissolve and apply the varnish no longer dissolves or even swells or softens the varnish. More "aggressive" solvents that will likely harm the original oil paint must be used to remove the varnish. To avoid this, the restorer carefully chooses solvents that have minimal swelling effect on the oil paint. However, this becomes increasingly complex if the oil paint contains substances other than simply oil, such as resins.
The Teas plots in Figures 1 and 2 include an estimate of the solubility of old, dried linseed oil paint. Dammar and mastic have different solubility parameters than dried linseed oil. If the painting contains dammar or mastic resin in the paint film, cleaning or removing the varnish may swell and soften the resins in the paint layer, resulting in damage or, worse, the removal of thin paint layers containing these resins.
Figure 3. Teas plot for a typical painting where the varnish is to be removed or applied without strongly affecting the underlying original oil painting. The solvents indicated are cyclohexane (C), heptane (H), and ethanol (E).
A resin that could be considered for use as a varnish on an oil painting is Paraloid B72, the tradename for a copolymer of ethyl methacrylate and methyl methacrylate (acrylic resin), often used by restorers and a component of some commercially-prepared varnishes for artists. There is a region in the lower right-hand corner of the plot in Figure 3 where the varnish is soluble, but the dried linseed oil paint is not. The solvent used to remove the varnish should be in this region. Mixtures of hydrocarbon solvent and ethanol are in this region and could be considered for the removal of this varnish.
The use of resins in oil paint can result in paint film embrittlement, cracking, or wrinkling due to differences in the drying mechanism of oils and resins. Oils harden by polymerization through the mechanism of oxidation while resins by evaporation of the solvent. Even if resins can be employed in oil paint without directly causing these problems, often their application is careless or haphazard at best as the artist mixes resin-based mediums or varnishes into the paint on the palette during the process of painting. More important is ignoring the complication that can arise during cleaning and varnishing by incorporating resins in oil paint.
Many painters today use resins in their paintings because they have been influenced by well-meaning artists and influential instructors, such as Jacques Maroger, who promoted using resin-based mediums in their paintings to achieve better handling properties in oil paint. They have done so without genuinely understanding the physical properties of these substances and considering the long-term consequences of their use when it comes time to clean and varnish their paintings.
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Which Rublev Colours oil painting mediums do not contain resins?
As part of our commitment to artists to provide full disclosure of our products, the following do not contain resins, waxes, or non-drying oils:
The following mediums contain small amounts of castor wax (less than 2% by weight):
The following mediums contain black oil and wax:
Giovanni Battista Armenini (1587) De Veri Precetti Della Pittura, Ravenna, Franç. Tebaldini, 1587, p. 124: '...il fumo di pece greca, il quale perche egli non hà corpo, s'incorpora benissimo col verderame ben macinato con oglio prima, del quale vi se ne mette un terzo & due di fumo...' Armenini also recommends the addition of a little varnish, probably the 'vernice commune' (essentially a varnish made with pine resin and oil) to which he refers elsewhere (p. 126). Some recipes for 'vernice commune' include Greek pitch as an ingredient: see, for example, Leonardo Fioravanti (1564) Del Compendio Dei Secreti Rationali..., Venice, Valgrisi, 1564, p. 172.
James Ayres (2014) Art, Artisans and Apprentices: Apprentice Painters and Sculptors in the Early Modern British Tradition, Oxford and Philadelphia: Oxbow Books, 2014, p. 131.
John Bannon (2015) "The Maroger Mediums vs. Meglip", Lavendera Fine Arts and Gifts, April 24, 2015, downloaded May 15, 2015.
David Bomford (2002) "'Secret Knowledge: Rediscovering the lost techniques of the Old Masters'," Book Review, The Burlington Magazine: A Centenary Anthology, Volume 145, Michael Levey, Editor, Yale University Press, 2003, p. 225.
Ian Bristow (1996) Interior Housepainting Colours and Technology, 1615–1840, New Haven and London: Yale University Press, p. 134.
John Burke (1984) "Solubility Parameters: Theory and Application," The Book and Paper Group Annual, Volume 3, 1984, The American Institute for Conservation, downloaded May 15, 2015.
Leslie Carlyle (2001) The Artist's Assistant: Oil Painting Instruction Manuals and Handbooks in Britain, 1800-1900, with Reference to Selected Eighteenth-Century Sources, London, Archetype Publications, 2001, pp. 101–106.
Malcolm Cormack (1970) "The Ledgers of Sir Joshua Reynolds," The Walpole Society, 1968–1970, Volume XLII, p. 141, folio 52 v.
Max Doerner (1963) The Materials of the Artist and Their Use in Painting, Harcourt Brace Jovanovich, 1984, p. 108.
William Donaldson (1768) The Life and Adventures of Sir Bartholomew Sapskull, Baronet: Nearly Allied to Most of the Great Men in the Three Kingdoms, Volume 1, J. Williams, 1768, p. 116.
Frederick Fairholt (1854) A Dictionary of Terms in Art, 1854. See Gumption, note, 'In the different treatises on painting and in the colourmen's catalogues we find it thus variously named... Magelp, magelph, magilp, magylp, magylph, megilp, megelp, megylp, megylph, macgelp, macgelph, macgilp, macgilph, macgylph, macgulp, magulp, megulph, mygelp, mygelph, mygilp, mygilph, mygulp, mygulph.'
Mark Gottsegen (2005) Book Review: "The Artist’s Assistant: Oil Painting Instruction Manuals and Handbooks in Britain 1800–1900 With Reference to Selected Eighteenth-Century Sources," Caa.reviews, May 4, 2005, downloaded May 15, 2015.
Charles Hansen (2007) Hansen Solubility Parameters: A User's Handbook, Second Edition, CRC Press, 2007, pp. 142–143.
M. Constant de Massoul (1797) A Treatise on the Art of Painting, and the Composition of Colours: Containing Instructions for All the Various Processes of Painting, Published by the author, Printed by T. Baylis, 1797, pp. 24–25.
Jacques Maroger (1948) The Secret Formulas and Techniques of the Masters, New York and London: Studio Publications, pp. 100, 168.
Lance Mayer, Gay Myers (2002) "Old Master Recipes in the 1920s, 1930s, and 1940s: Curry, Marsh, Doerner and Maroger," Journal of the American Institute for Conservation, Volume 41, Number 1, Article 3, pp. 21–42.
Lance Mayer, Gay Myers (2011) American Painters on Technique: The Colonial Period to 1860, Getty Publications, 2011, pp. 11, 49–50.
Lance Mayer, Gay Myers (2013) American Painters on Technique: 1860–1945, Getty Publications, 2013, pp. 211–213.
Ralph Mayer (1949) "The Secret Formulas and Techniques of the Masters", Book Review, Magazine of Art, Volumes 42–43, American Federation of Arts, p. 73.
Ralph Mayer (1975) The Painter's Craft: An Introduction to Artists' Methods and Materials, Third Edition, Viking Press, 1975.
Ralph Mayer, Steven Sheehan (2001) The Artist's Handbook of Materials and Techniques, Fifth Edition, Viking, 1991.
Rachel Morrison (2010) "Mastic and Megilp in Reynolds’s 'Lord Heathfield of Gibraltar'", National Gallery Technical Bulletin, Volume 31, Ashok Roy, Editor, National Gallery Company, Ltd., 2010, pp. 112–128.
Alan Phenix, Richard Wolbers (2013) "Removal of Varnish: Organic Solvents as Cleaning Agents", Conservation of Easel Paintings, Joyce Hill Stoner, Rebecca Rushfield, Editors, Routledge, 2013, pp. 524–534.
Jean Teas (1968) "Graphic Analysis of Resin Solubilities," Journal of Paint Technology, Volume 40, Number 516, 1968.
Jean Teas (1971) Predicting Resin Solubilities, Columbus, Ohio: Ashland Chemical Technical Bulletin, Number 1206.
Joyce Townsend (1995) "Painting Techniques and Materials of Turner and Other British Artists 1775–1875", Historical Painting Techniques, Materials, and Studio Practice: Preprints of a Symposium, University of Leiden, the Netherlands, 26–29 June 1995, Arie Wallert, Erma Hermens, Marja Peek, Editors, Getty Publications, 1995, pp. 176–185.
Joyce Townsend (1995) "Turner's Use of Materials, and Implications for Conservation," Turner's Painting Techniques in Context, 1995, Joyce Townsend, Editor, London, 1995, pp. 7–10.
Joyce Townsend, Leslie Carlyle, A. Burnstock, M. Odlyha, Jaap Boon (1998) "Nineteenth-Century Paint Media: The Formulation and Properties of Megilps", Painting Techniques: History, Materials and Studio Practice, Contributions to the Dublin IIC Congress 7–11 September 1998, Ashok Roy, P. Smith, Editors, London, 1998, pp. 205–210.
Raymond White, Jo Kirby (1994) "Rembrandt and his Circle: Seventeenth-Century Dutch Paint Media Re-examined," National Gallery Technical Bulletin, Volume 15, Ashok Roy, Editor, National Gallery Company, Ltd., 1994, pp. 64–77, especially pp. 71–3.
Raymond White, Jennifer Pilc (1996) "Analyses of Paint Media," National Gallery Technical Bulletin, Volume 17, Ashok Roy, Editor, National Gallery Company, Ltd., 1996, pp. 91–103.
Raymond White, Jennifer Pilc, Jo Kirby (1998) "Analyses of Paint Media," National Gallery Technical Bulletin, Volume 19, Ashok Roy, Editor, National Gallery Company, Ltd., 1998, pp. 74–95.
William Whitley (1928) Artists and their Friends in England 1700–1799, Volume 2, London and Boston, 1928, p. 282.
Nathaniel Whittock (1827) The Decorative Painters' and Glaziers' Guide. pp. 21–22.