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Staying Grounded: The Importance of Priming

The thought of priming has become a distant thought for most painters today. With the broad availability of pre-primed, ready to use, and generally economical supports, it is understandable why this part of painting has fallen by the wayside. Since its advent in the 1950s, acrylic gesso has slowly become the choice primer of acrylic and oil painters. Although it may seem like simple white paint, acrylic gesso is a truly modern material that has solved centuries of technical issues faced by fraught painters. Today acrylic gesso is widely available on nearly every pre-primed support. It is success however is not without caveats. Today at Tri-Art we continue to receive reports of paintings failing due to poor quality priming layers. Today’s article explores the history of ground layers and how artists can select and prepare priming layers to ensure their work stand the test of time.

FOUNDATIONAL: A PRIMER ON GROUND LAYERS

A ground, primer, or preparatory layer is the initial surface laid down by the artists upon their support. It can consist of multiple layers of the same or different materials, built up to achieve a desired effect. When it comes to colour, white grounds have been widely exploited because of their optical effect – when applied thickly enough, they reflect light, giving vibrancy to the colours painted on top of them.[1] This effect was masterfully exploited in the 19th century by the Pre-Raphaelite Brotherhood of painters. These painters sought the brightest pure white ground to reflect light through their painstaking application of glazed oil colour. Additionally, the white ground played a critical role in not only creating their works, but also preserving them. As paintings age, ground layers generally remain white while canvas darkens with age. White grounds therefore are responsible for retaining the brilliancy of colour in painting over time.[2]

Ophelia, painted by John Everett Millais. A painting of a woman singing while she drowns in water.

Ophelia, by John Everett Millais, 1851–52. Tate Museum, London. Image Via WikiCommons. A prime example of the Pre-Raphaelite Brotherhood, Millais utilized a white ground upon which he built vibrant, translucent layers of oil colour.

Beyond their aesthetic and optical properties, it is important to note that grounds are not just initial layers of paint, but often unique materials that provide important functionality to paintings. Primers, gessoes, and grounds are used in place of paint for their ability to modify the tooth, absorbency, and texture of a support. They provide a uniform layer that will accept the paint with consistency, often preventing its sinking into absorbent supports like wood or canvas and aiding its wetting onto slippery supports like plastic and aluminum. When it comes to oil painting on canvas, grounds serve the critical function of creating a barrier between the acidic oil and canvas. If allowed to come into contact, the acids in oil accelerate the deterioration of canvas, turning it dark, brittle, and fragile.[3]

It has long been understood that the quality of a ground layer will determine both the aesthetic success and long-term survival of a painting. Throughout time artists have readily adapted their materials to achieve surface texture, absorbency, and colour, but have also been keenly aware of the risks of discoloration, flaking and cracking. It’s hard to understate the vast quantity of artists’ treatises and manuals that argue the pitfalls and virtues of using one priming over another. For instance, in the 17th century painters widely utilized a dark reddish-brown ground. For painters like Caravaggio, it gave immediacy to painting by providing a mid-tone that could be used in the final composition. However, by the 18th century it was understood that oil paint gained considerable translucency with age; paintings with dark grounds were seen to be swamped by their red-brown grounds that overtook the tonal balance of the composition with time. Grounds shifted generally to light gray or white with an aim to avoid this colour change. [4]

Cristoforo Savolini, Italian, 1639 – 1677. The Expulsion of Hagar, possibly 1670’s. Oil on canvas. 40 x 37 in. (101.6 x 94 cm). Gift of Mrs. Baylor O. Hickman, 1970.43. Speed Art Museum, Louisville. Dismissal of Hagar and Ishmael, possibly 1670’s. Pushkin Museum, Moskow. Both images via WikiCommons. These two works from the same series, one unfinished, show how 17th century artist would utilize red-brown grounds when painting. Notice the red undertones showing through, particularly evident in the stonework.

Cristoforo Savolini, Italian, 1639 – 1677. The Expulsion of Hagar, possibly 1670’s. Oil on canvas. 40 x 37 in. (101.6 x 94 cm). Gift of Mrs. Baylor O. Hickman, 1970.43. Speed Art Museum, Louisville. Dismissal of Hagar and Ishmael, possibly 1670’s. Pushkin Museum, Moskow. Both images via WikiCommons. These two works from the same series, one unfinished, show how 17th century artist would utilize red-brown grounds when painting. Notice the red undertones showing through, particularly evident in the stonework.

Today, most viewers would probably deem these changes as acceptable and understand them as part of the natural aging of a painting. Beyond colour changes though, most historical paintings, and even many 20th century modern paintings, have needed some amount of intervention to stabilize cracked, flaking paint. This is nearly always the fault of sizing and ground layers,[5] and makes clear the point – priming is critical to the success and survival of your work.

HIDING IN PLAIN SIGHT: TRADITIONAL GESSOES

Understanding the priming materials of the past and the technical problems that artists faced while using them offers us the clearest understanding of how and why to use modern materials. Today most artist use acrylic ‘gesso’. Gesso is the traditional term for priming applied to Italian panel paintings. The mixture was usually comprised of animal hide glue and white gypsum. It was coopted in the 1950s for acrylic priming, despite having little in common other than its purpose as a ground layer.[6] Many other historical formulations can be found across space and time: several choices of white pigments, bound in flour, animal glue, or drying oil with other additions to modify absorption, flexibility, and adhesion. Glue-based grounds remained a popular mainstay of easel painting since its advent because they offered critical properties for oil painting, mainly absorbency and colour permanence. By removing excess oil from the paint layers above, painters believed that water-based glue grounds could keep a painting looking as fresh as possible for as long as possible, as excess oil darkens over time. Additionally, glue-based grounds themselves did not discolour greatly over time.[7]

Historical treatises on these grounds are extensive and nebulous. What emerges as a clear trend, however, is the technical struggle that artists faced when preparing supports for painting. Glue grounds presented a high risk of flaking, especially if applied too thickly. They were also inflexible, and therefore had a high tendency to crack when rolled for transport.[8] When it comes to the long-term consequences of using a glue ground, these layers are often responsible for the cracking and flaking loss of paint layers. Animal glue grounds tend to be brittle, cracking in response to physical forces or stresses caused by changing humidity over the year. Like a bridge that expands and contracts slightly in the summer and winter, the many component parts and layers of a painting experiences similar dimensional changes as temperature and humidity fluctuates. The hygroscopic animal glue of a traditional glue ground is particularly reactive to these fluctuations in humidity, expanding or contracting enough to place significant shear stress on the bond between paint and ground. Oil paint, with little adhesive strength to begin with, has even less affinity to these water-based glue layers, and so under this stress is liable to flake off the ground under these conditions. At extremely high humidity the effects can be particularly devastating to works on animal glue grounds as animal glue simply reaches a point that it loses all adhesive strength and becomes swollen with moisture.[9] Many historical works are now preserved in carefully climate-controlled settings like museums and galleries to prevent this process from further occurring.

The absorbency of these ground layers appeared to be a double-edged sword. In an era before fast drying paints, an absorbent glue ground offered a means to expedite painting. By absorbing oil from the first layer of colour, it offered the means to rapidly lay down an initial sketch before moving onto more substantial paint layers. However, historical sources also site the challenges of dealing with the resulting tonal shifts and their paint quickly becoming stiff and unworkable upon the canvas. From the 16th century onward an initial glue ground could often be modified with an additional ground layer of oil or glue to reduce its absorbency and potentially add a wash of colour. To find a better balance between absorbency and flexibility, more flexible oil paint, or emulsions of oil and glue were also utilized on their own as ground layers.[10] Oil grounds were also less susceptible to changes in humidity but had their own caveats. Oil and emulsion grounds show more­­ discoloration over the short-term than glue and eventually become inflexible as they age. They also did not have the ability to pull a canvas taught as they dried, one of the hallmarks of animal glues and grounds. Centuries old oil priming layers undergo fascinating chemical changes that render them increasingly transparent. This can result in the appearance of wood grain in panel paintings, dark streaks, or the general darkening of paintings as the reflective ground is lost, particularly if a darker ground layer has been applied beneath the white layer. The chemical changes of the oil grounds can also result in a loss of adhesion, leading to flaking.[11]

Painting by Rembrandt, the Anatomy Lesson. A group of students in Dutch 17th century garb watch closely as a man holds the dissected arm tendons of a corpse

Rembrandt van Rijn (1606 – 1669), The Anatomy Lesson of Dr Nicolaes Tulp. 1632. Mauritshuis Museum, Amsterdam. Image via WikiCommons. An example of 17th century work effected by an oil ground slowly becoming more transparent, the work is darkening.

We can start to put together a picture of why traditional grounds are so problematic in their own way. With all the issues they had to overcome, we can understand why accounts of artists, colourmen, professional primers, restorers and the likes detailed the laboured effort it was to prevent paintings from falling apart.

PLASTIC MAKES PERFECT: MODERN ‘GESSO

The solutions attempted by artists in the past to solve their technical problems were quite nearly endless: flour paste grounds, additions of shellac, dusting dry pigments onto a wet ground, or even painting into a wet ground. By the 20th century new solution became available with advancements in chemistry and post-World War industrialization.

In the mid 1950s, acrylic gessoes were developed by Permanent Pigments under the brand Liquitex.[12] Modern acrylic gesso has little in common with historical gesso, instead this modern ground utilizes a mixture of acrylic dispersion, thickeners, white pigments (typically titanium dioxide, also an invention of the 20th century), and other additives like calcium carbonate (chalk) to increase absorbency and give tooth the final surface.

Acrylic gesso is truly more stable than any other priming to come before it. Unlike glue, oil, or natural resins that become brittle and fragile over time, acrylic remains flexible. Because of this it is not liable to ground cracking or flaking.[13] Additionally this chemical stability ensures that it does not discolor and suggests it should retain its opacity over time. Perhaps above all, for most artist today, it is acrylic’s ease of use where it truly shines. Whereas glue and oil grounds needed to be carefully and thinly applied to avoid flaking, acrylic gesso can be applied very thinly or thickly, while retaining flexibility and good adhesion to the support. Acrylic grounds can be modified with more filler like calcium carbonate to add tooth and absorbency, coloured with acrylic paint, or mixed with mediums like modeling paste to give it heavy texture.

peaked white modeling paste

Tri-Art modeling paste is an excellent tool to add texture to your ground layer.

Acrylic gesso ultimately fulfilled a technological gap in the world of artists’ materials. Major manufactures began phasing out oil primed grounds in the 1970s,[14] with acrylic now certainly the most popular choice. There is hardly any downside to selecting an acrylic ground to work with, but as with all art materials, quality does play a part.

Cheaper grades of acrylic or vinyl, often found in economical house paints, may contain unstable polymers that cause the paint film to become brittle and yellow over time – these should be avoided, particularly when working on flexible supports like canvas where cracking is more likely.[15]  Particularly primer and matte formulations, containing a great deal of filler pigment, will ultimately fail at much lower tensile strengths, likely resulting in cracked turn over edges, and potentially cracking across the picture plane.[16]

When using acrylic gesso, it is also not necessary to size a canvas or support, but it is highly advisable. Users report a phenomenon coined Support Induced Discoloration (SID), the migration of water-soluble components from canvases, panels or others supports into acrylic gesso as it dries.[17] Applying a dilute layer of acrylic medium to your support before priming will seal the surface against any discoloration and greatly help tighten a canvas.

THE PITFALLS OF PRE-PRIMED SUPPORTS

Today many artists will be tempted to reach for the most economical choice of supports, often canvas boards or pre-stretched canvases that come pre-primed in multipacks. These may cost little upfront, but do they pay off in the long run?

The notion of buying pre-primed canvas is quite old. In fact, by the 17th century most priming was undertaken by professionals outside the artist’s studio across Europe. By the 19th century pre-primed canvases were standard issues – white grounds were available in a range of materials and canvases in a range of sizes.[18] Concerns of quality in these products was already quite apparent by the mid 18th century with reports of manufacturers cutting corners to make profits and faulty workmanship leading to a less than desirable product. Poor quality canvases primed with oil grounds were said to come still wet, but also rancid, smelling terrible. An overuse of oil driers in these canvases was said to further cause the white grounds to become yellow, gritty and brittle.[19] To ensure the quality of their canvases’ artists like Turner, Renoir and Monet instead all prepared their own supports.[20]

painting by Monet, woman with a parasol. She stands in a windy field with clouds.

Claude Monet, Woman with a Parasol – Madame Monet and Her Son, 1875, National Gallery of Art, Washington, D.C. Monet was known to prime his own canvases.

Today, Tri-Art has found that commercially pre-applied acrylic gesso supports can also be of unacceptably low quality.[21] Economical pre-primed supports may be tempting options, but they also may lack exhibit a dullness in color, a high degree of brittleness, a tendency to crumble, a resistance to wetting, and a lack of adhesion between canvas, ground, and paint layers.  These issues can likely be explained by a lack of high-quality acrylic binder and a lack of titanium white pigment. In excess, extender pigments used in place of titanium white yield a greyish-white coloured primer.[22]

A lack of acrylic binder can likely explain issues with crumbling and adhesion. This lack of acrylic binder is also often betrayed by a lack of water resistance.[23] This makes these supports problematic from the outset, but also later as fingerprints and dust are not easily cleaned from these fragile surfaces.[24] In lieu of quality acrylic, particularly inexpensive pre-primed supports may utilize other less expensive resins that are brittle, yellowing, and even water soluble. Vinyl emulsions containing unstable polymers like PVC are one such cause for concern. These brittle resins require considerable amounts of plasticizer, comprising up to 40% of their weight.[25] Today phthalates and other plasticizers remain critical in PVC paint formulations.[26] These primers make a poor choice for artists for many reasons, but particularly as the heavy plasticizer content is liable to exude over time. This is likely to interfere with the adhesion of paint layers, create surface haze, and return the PVC to its naturally brittle state.

A quick litmus test for quality gesso is simply to try wiping the surface with a wet sponge or rag. If the gesso is of poor quality, white particles will readily lift away from the surface.[27] This has the added benefit of removing any water-soluble sizing layer that has been applied by the manufacturer to prevent these canvases from sticking together during transit. Most importantly though wiping your supports down will remove excess surfactant from the surface. All acrylics are made with surfactants that are generally in excess once the paint or gesso is dry. These surfactants can migrate to the surface causing issues with adhesion, gloss, and clarity of applied paint films. Particularly when left to sit in dark storage (like in warehouses or store backrooms), these surfactants will migrate to the surface. The good news is they can be readily and safely removed with water.[28]

A spray bottle and cloth.

Simple tools for effective results. A lint free cloth and spray bottle allow painters to remove any excess surface surfactants without fuss before painting. This ensures an excellent bond between paint and primer.

Here is a comparison between a very inexpensive pre-primed canvas purchased at a discount store and Tri-Art’s artists’ quality pre-primed eco-canvas. The discount canvas is unusually stiff and inelastic – simply folding the canvas over itself fractures the priming and creates a sharply held fold line. Conversely, Tri-Art’s 100% acrylic gesso retains the flexibility of canvas – it can be aggressively folded and still barely holds a crease, let alone cracking. It is also tough, with aggressive washing producing little change when tested. In comparison the discount canvas priming was water soluble, producing a milky run off when rubbed with a wet cloth. After washing pinholes can be seen in the canvas where priming has been completely lost.

two canvas samples folded for testing. The left is largely flat and slightly creased, the right, from a discount store is creased and holding its shape like a sheet of stiff paper.

Fold Test: Tri-Art Pre-Primed Eco-Canvas vs. Discount Store Pre-Primed canvas. The discount store canvas is very brittle and folds like paper.

four canvas swatches from a water washing test. the discount store swatch shows less primer and pinholes after washing, the tri-art one shows negligible change.

Wash test: Discount store pre-primed canvas ontop showed immediate lack of water resistance when wipe with a wet cloth. Aggressive washing with water removed a great deal of the primer, producing pinholes in the revealed canvas. Tri-Art’s pre-primed canvas remained practically unchanged after aggressive washing.

When it comes to the possible issues of less-than-ideal quality in pre-primed supports, it is always better to prime your own if possible or buy from reputable manufacturer. If your pre-primed canvas is of dubious quality the stability of your work will always be tenuous and will not be solved with more coats of paint or primer. Here at Tri-Art, we prime all our supports with our highest quality artists gesso without exception. We encourage our artists to primer their own supports and explore the many potential surfaces possible with acrylic gesso.

brushing white paint onto a pre-primed canvas

Don’t be afraid to modify an existing surface to suit your needs. Tri-Art Eco-Canvas with a thin coat of Tri-Art High Viscosity Titanium White.

OIL AND WATER: MIXED MEDIA APPLICATIONS

Some oil painters have a deep connection to the material history of their medium and an even deeper distrust of the modern. As explored before historical options for primings consisting of animal glues, drying oils, and natural resins all have limitations and issues when it comes to application, use and aging. Acrylic solved these issues, but is it compatible with oil paint?

First, animal glue grounds are simply not available commercially and must be prepared by oneself if you wish to explore using them. When considering their sensitivity to changes in humidity and their tendency to crack and flake these grounds are no longer advisable for practicing artists.  Anyone who has worked with traditional animal glues or gesso will know that the smell alone is enough to switch to acrylic gesso. Unpleasant to say the least, animal glues are also susceptible to bacterial and mold overgrowth that ruin them. They must also be applied warm, also making them liable to overheating and breakdown (think of when your Jell-O® recipe fails). Furthermore, artists might just feel uncomfortable using animal derived products in their work. Today’s oil painters largely have the choice between alkyd modified oil priming or acrylic gesso.

Unfortunately for the traditionalists, acrylics outperform alkyds on nearly every front. By far acrylic grounds greatest advantage over oil is their adhesion to water-based sizing layers applied to the canvas. Oil and alkyd have little adhesive strength, particularly to water-based materials and may delaminate over time.[29] These sizing layers are necessary when applying oil and alkyd grounds to isolate the support from the acidic content of the oil. Their lack of adhesion immediately poses a long-term risk to the security of oil and alkyd grounds. Despite this, oils and alkyds still adhere very well to acrylic gesso, likely due to its absorbency. This research comes not just from the short term, or controlled lab experiments. An extensive survey of the Tate’s collection found half of oil paintings post 1963 were painted on acrylic grounds. None of these works were found to exhibit adhesion issues.[30]

Acrylics also outperform alkyds when it comes to flexibility. Even when aged, acrylic emulsion grounds should survive some degree of bending and straining. Alkyd grounds on the other hand are not very flexible, making them vulnerable to cracking on the folder over edge and across the surface. [31] This effect is exacerbated in the cold Canadian climate, as alkyd primers show little plasticity below 30-40 °C.  Acrylic grounds are much more suited to the cold, remaining somewhat flexible to as cold as 0 °C. [32] Acrylics are in fact so flexible they can impart some of this quality to oil and alkyd layers painted on them. By increasing the flexibility of oil paintings, acrylic gesso can prevent cracking over time.[33]

Lastly acrylics will certainly outperform alkyd grounds when it comes to colour retention. Alkyds and oils have a natural tendency to slightly yellow, even in the short-term. White acrylic gesso will retain its white colour for much longer, functioning as a brilliant optical reflector for light through your painting.

As with any choice of material, there are caveats to painting in oil over acrylic. When it comes to using solvents, mediums and varnishes, acrylic grounds must also be considered. Acrylic is often soluble in solvents like xylenes and turpentine. While most artists no longer use these in their painting practice, these are still commonly found in acrylic and dammar varnishes formulated for oil paintings. A better alternative for paintings on acrylic gesso would be varnishes and mediums containing only odorless mineral spirits, especially if you have left areas of the ground exposed. Make sure to always test your varnish in discrete areas before applying it to whole surface.

Additionally, with oil on acrylic, support reuse is particularly limited. Some online tutorials suggest that oils can be scraped down and sanded before reapplying more acrylic gesso. This may well work in the short-term, but the adhesion of the acrylic to oily layers (including acrylic gesso that has absorbed oil from the applied paint layers) will always be tenuous. When it comes to reusing supports, it is best to either remove all paint and ground layers, by sanding back down to the wood of a panel for instance, or just using these supports for process work that is not intended to be finished or permanent work.

PRIMING: PRACTICAL TIPS FOR ARTISTS

  •  The current research – both from collections surveys of early acrylic use, and lab work – shows acrylic grounds are a very stable, sound choice for any paint medium. It is likely the ideal choice for your work.
  • Whenever possible apply your own sizing and/or acrylic priming layers to ensure that you are using a quality product, like Tri-Art artists’ gesso. Always refer to product labels. Look for products labeled as 100% acrylic polymer emulsion. Do not use wall primer which is meant for a rigid support and not formulated to be archival – its lack of flexibility can ultimately cause cracking and flaking from a flexible support like canvas.
  • When in doubt about a gesso, or if trying your own modified acrylic ground formula, you can easily test your gesso by pouring out a small puddle on a piece of paper or scrap of canvas – once dry, try flexing it. If it cracks. Do not use it on a flexible support like canvas.[34]
  • Sizing and priming are much more economical than paint – if economy is important to you, then ensure that your support is well prepared and that no pigment goes to waste
  • It is always best to size your support to prevent discoloration from migrating into your ground and paint layers – this is particularly true for wood panels, canvases and any atypical supports that may have water soluble colourants. Use a high-quality acrylic product to ensure the best results.
  • All acrylic paint contains surfactants, generally that are in excess once the paint is dry. To ensure an excellent bond between paint and priming, use a damp sponge or cloth to wash away any excess surfactant, particularly from all pre-primed supports. This will also wash away any sizing left by the manufacturer. Be careful not to use so much water as to warp wood or canvas panels.
  • When using atypical supports always test the adhesion of your intended size, ground, or paint layers. Adhesion may take up to two weeks to develop as the acrylic fully dries.
  • Due to its porous nature, acrylic gesso is more fragile and difficult to clean than acrylic paint.[35] If you plan to keep a significant part of the ground exposed in your composition consider laying down a thin layer of acrylic paint across the whole support before painting your design.

[1] Stephen Hackney, On Canvas : Preserving the Structure of Paintings (Los Angeles: The Getty Conservation Institute, 2020).

[2] M D Gottsegen, ‘Sizes and Grounds’, in The Painter’s Handbook: A Complete Reference (Watson-Guptill Publications, 2006), pp. 51–72 <https://books.google.ca/books?id=o23u0SuRLxsC>.

[3] Gottsegen.

[4] Maartje Stols-Witlox, A Perfect Ground : Preparatory Layers for Oil Paintings, 1550-1900  (London: Archetype Publications, 2017).

[5] Hackney.

[6] ‘Sizes and Grounds’, Gamblin Artists’ Colors <https://gamblincolors.com/oil-painting/sizes-and-grounds/> [accessed 26 April 2021].

[7] Stols-Witlox.

[8] Stols-Witlox.

[9] Hackney.

[10] Stols-Witlox.

[11] Petria Noble, Annelies van Loon, and Jaap J Boon, ‘Selective Darkening of Ground and Paint Layers Associated with the Wood Structure in Seventeenth-Century Panel Paintings’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend and others (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.68-78, 7 figs. (6 color), 1 table, 12 notes, re.

[12] Maartje Stols, Bronwyn Ormsby, and Mark Gottsegen, ‘Grounds, 1400-1900 – Including: Grounds in the Twentieth Century and Beyond’, in The Conservation of Easel Paintings, ed. by Joyce Hill Stoner and Rebecca Rushfield, Second (Abingdon: Routledge, 2021), pp. 163–91.

[13] Hackney.

[14] Stols, Ormsby, and Gottsegen.

[15] Hackney.

[16] Eric Hagan and others, ‘Factors Affecting the Mechanical Properties of Modern Paints’, in Modern Paints Uncovered: Proceedings from the Modern Paints Uncovered Symposium, ed. by Thomas J S Learner and others (Los Angeles: Getty Conservation Institute, Los Angeles, United States, 2007), p. pp.227-235, 8 figs., 4 tables, refs.

[17] Gottsegen.

[18] Stols, Ormsby, and Gottsegen.

[19] Stols-Witlox.

[20] Stols, Ormsby, and Gottsegen.

[21] ‘Why We Recommend Unprimed Canvas’, Art Noise <https://shop.artnoise.ca/blogs/art-noise-handbook/why-we-recommend-unprimed-canvas> [accessed 26 April 2021].

[22] Hackney.

[23] D G Kelly, ‘The Effect of Water Resistance on the Durability of Waterborne Coatings’, Paint & Coatings Industry, 19 (2003), 38.

[24] Stols, Ormsby, and Gottsegen.

[25] A Jayakrishnan, M C Sunny, and Mini N Rajan, ‘Photocrosslinking of Azidated Poly(Vinyl Chloride) Coated onto Plasticized PVC Surface: Route to Containing Plasticizer Migration’, Journal of Applied Polymer Science, 56.10 (1995), 1187–95 <https://doi.org/https://doi.org/10.1002/app.1995.070561001>.

[26] Richard Pearce, ‘Dispersing Pigment/Filler Concentrates in Plasticizer Dispersions’, Plastics, Additives and Compounding, 6.4 (2004), 36–39 <https://doi.org/https://doi.org/10.1016/S1464-391X(04)00238-7>.

[27] Rheni Tauchid, New Acrylics Essential Sourcebook : Materials, Techniques, and Contemporary Applications for Today’s Artist  (New York: Watson-Guptill Publications, 2009).

[28] Bronwyn A Ormsby and others, ‘Comparing Contemporary Titanium White-Based Acrylic Emulsion Grounds and Paints: Characterisation, Properties and Conservation’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend and others (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.163-171, 5 figs., 5 tables, 5 notes, refs.

[29] Hackney.

[30] Ormsby and others.

[31] Christina Young, ‘Interfacial Interactions of Modern Paint Layers’, in Modern Paints Uncovered: Proceedings from the Modern Paints Uncovered Symposium, ed. by Thomas J S Learner and others (Los Angeles: Getty Conservation Institute, Los Angeles, United States, 2007), p. pp.247-256, 7 figs. (5 color), 3 tables, refs.5.

[32] Christina Young and Eric Hagan, ‘Cold Temperature Effects of Modern Paints Used for Priming Flexible Supports’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend and others (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.172-179, 7 color figs., 2 tables, 4 notes, refs.

[33] Young.

[34] Rheni Tauchid, Acrylic Painting Mediums & Methods : A Contemporary Guide to Materials, Techniques, and Applications Acrylic Painting Mediums and Methods, First edit (New York, New York: Monacelli Studio, 2018).

[35] Ormsby and others.

BIBLIOGRAPHY

Gottsegen, M D, ‘Sizes and Grounds’, in The Painter’s Handbook: A Complete Reference (Watson-Guptill Publications, 2006), pp. 51–72 <https://books.google.ca/books?id=o23u0SuRLxsC>

Hackney, Stephen, On Canvas: Preserving the Structure of Paintings (Los Angeles: The Getty Conservation Institute, 2020)

Hagan, Eric, Maria Charalambides, Thomas J S Learner, Alison Murray, and Christina Young, ‘Factors Affecting the Mechanical Properties of Modern Paints’, in Modern Paints Uncovered: Proceedings from the Modern Paints Uncovered Symposium, ed. by Thomas J S Learner, Patricia Smithen, Jay W Krueger, and Michael R Schilling (Los Angeles: Getty Conservation Institute, Los Angeles, United States, 2007), p. pp.227-235, 8 figs., 4 tables, refs.

Jayakrishnan, A, M C Sunny, and Mini N Rajan, ‘Photocrosslinking of Azidated Poly(Vinyl Chloride) Coated onto Plasticized PVC Surface: Route to Containing Plasticizer Migration’, Journal of Applied Polymer Science, 56.10 (1995), 1187–95 <https://doi.org/https://doi.org/10.1002/app.1995.070561001>

Kelly, D G, ‘The Effect of Water Resistance on the Durability of Waterborne Coatings’, Paint & Coatings Industry, 19 (2003), 38

Noble, Petria, Annelies van Loon, and Jaap J Boon, ‘Selective Darkening of Ground and Paint Layers Associated with the Wood Structure in Seventeenth-Century Panel Paintings’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend, Tiarna Doherty, Gunnar Heydenreich, and Jacqueline Ridge (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.68-78, 7 figs. (6 color), 1 table, 12 notes, re

Ormsby, Bronwyn A, Eric Hagan, Patricia Smithen, and Thomas J S Learner, ‘Comparing Contemporary Titanium White-Based Acrylic Emulsion Grounds and Paints: Characterisation, Properties and Conservation’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend, Tiarna Doherty, Gunnar Heydenreich, and Jacqueline Ridge (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.163-171, 5 figs., 5 tables, 5 notes, refs.

Pearce, Richard, ‘Dispersing Pigment/Filler Concentrates in Plasticizer Dispersions’, Plastics, Additives and Compounding, 6.4 (2004), 36–39 <https://doi.org/https://doi.org/10.1016/S1464-391X(04)00238-7>

‘Sizes and Grounds’, Gamblin Artists’ Colors <https://gamblincolors.com/oil-painting/sizes-and-grounds/> [accessed 26 April 2021]

Stols-Witlox, Maartje, A Perfect Ground: Preparatory Layers for Oil Paintings, 1550-1900  (London: Archetype Publications, 2017)

Stols, Maartje, Bronwyn Ormsby, and Mark Gottsegen, ‘Grounds, 1400-1900 – Including: Grounds in the Twentieth Century and Beyond’, in The Conservation of Easel Paintings, ed. by Joyce Hill Stoner and Rebecca Rushfield, Second (Abingdon: Routledge, 2021), pp. 163–91

Tauchid, Rheni, Acrylic Painting Mediums & Methods: A Contemporary Guide to Materials, Techniques, and Applications Acrylic Painting Mediums and Methods, First edit (New York, New York: Monacelli Studio, 2018)

———, New Acrylics Essential Sourcebook: Materials, Techniques, and Contemporary Applications for Today’s Artist  (New York: Watson-Guptill Publications, 2009)

‘Why We Recommend Unprimed Canvas’, Art Noise <https://shop.artnoise.ca/blogs/art-noise-handbook/why-we-recommend-unprimed-canvas> [accessed 26 April 2021]

Young, Christina, ‘Interfacial Interactions of Modern Paint Layers’, in Modern Paints Uncovered: Proceedings from the Modern Paints Uncovered Symposium, ed. by Thomas J S Learner, Patricia Smithen, Jay W Krueger, and Michael R Schilling (Los Angeles: Getty Conservation Institute, Los Angeles, United States, 2007), p. pp.247-256, 7 figs. (5 color), 3 tables, refs.5

Young, Christina, and Eric Hagan, ‘Cold Temperature Effects of Modern Paints Used for Priming Flexible Supports’, in Preparation for Painting: The Artist’s Choice and Its Consequences, ed. by Joyce H Townsend, Tiarna Doherty, Gunnar Heydenreich, and Jacqueline Ridge (London: Archetype Publications Ltd., London, United Kingdom, 2008), p. pp.172-179, 7 color figs., 2 tables, 4 notes, refs

Categories
Creative Zone Blog

Cracked Glaze Effect House

Cracked Glaze Effect on Tiny House

House painted and displaying cracked effects

MATERIALS:
Art Noise Permanent Acrylic Gouache paints
Tri-Art’s Crackle Ground Acrylic Medium

Tri-Art’s Liquid Iridescent Copper
Nylon brush (1/2 or 1”)
Wooden 3D puzzle house

INSTRUCTIONS
STEP 1
Prime and paint house surface with gesso or  Art Noise paint. This will be the colour revealed between the cracks once the Crackle Ground dries.

Allow to dry before adding Crackle Ground Medium.

STEP 2 
Apply Crackle Ground onto one side (surface) at a time. Surfaces must be horizontal or the medium will run off the surface. Apply a generous amount by pouring and then tilt the surface to spread or pour and spread with a brush. Using a small cup to pour gives more control. If using brush, very light pressured strokes must be used or the cracks will not happen. Let each side dry before adding the medium to other sides. 

STEP 3
Once dry the primed house colour will be revealed in the cracks. Paint may be applied over the white Crackle Ground. This should be done in light coats with either a brush or rag to avoid filling in the cracks with paint.

Applying paint in mutiple thin layers, glazing, dry brushing and blending techniques will accentuate the cracks and enhance the glazed effects. 

Categories
Education Notes from the Lab

Beyond Colour: The Rheology and Viscosity of Acrylic Paints

In the post-modern era of social media sharing and digital art, the physical, material properties of paints often take a back seat to the immediacy of their colour. Today’s acrylic paint comes formulated in a range of mediums from free flowing, ink-like forms to highly bodied, gel types. Each has their purposes, that can either aid, or work against the artist in bringing to life their vision. Rheology and viscosity are the key properties that form the real structure and working properties of acrylic while pigment is essentially decorative, a metaphoric coat of paint over the architectural acrylic armature.

While perhaps too technical sounding for some painters, learning these concepts will pay dividends to those who wish to truly understand their medium and how to build a painted surface. In addition to creating new work, these concepts offer a window of understanding to the works of the past – both to the grand tradition of painting in oil, and to the modern experimentations of 20th century artists. Today’s contemporary formulations of acrylic paint have come a long way to find the best from both of these domains, encompassed by Tri-Art’s philosophy for artist’s finest quality acrylic paint.

The Basics: The Long and Short of Rheology

Viscosity is the measure of a fluid’s resistance to flow under applied force. It’s an intuitive measure of simply how thick or thin a liquid is. Viscosity, however, is the greyscale of paint properties in a colourful world of other paint behaviours. Rheology is one of the true superstars. Analytically, it describes a fluid’s deformation and flow under applied stress.

Paints with long rheology are flowing and stringy, like honey and glue. The force of gravity alone is enough to make long rheology paints flow after they dry, resulting in softened edges and smooth surfaces devoid of brush marks. This is often utilized in self-leveling formulas for wall paint, primers, or artist’s gesso. Traditional painting techniques like Indian Rogan for textiles also utilize this stringy rheology to great effect in complex designs.

Fluids with short rheology, in contrast, are unable stretch or flow. They are often better described as ‘soft solids’ – meaning the physical action of a brush or palette knife results less in flow, and more in the paint being deformed around the artist’s tool, recording the act of mark making.[i] When a tool is lifted from the surface of these paints, the paint reaches a quick breakpoint, resulting in stiff peaks and veining. This behaviour was long the coveted purview of oil paint.

The Writing is in the Rheology: Reading Historical Brushwork in Oil Painting

Since its advent, painters have been exploring the rheological properties of oil paints. In its purest form, high-quality oil paints have a very short rheology. It preserves an incredibly high-fidelity record of an artist’s marks on a canvas. Think of Jean-Paul Riopelle’s sculptural taches, Rembrandt’s thickly piled white highlights, and Van Gogh iconic brushwork. The three-dimensional quality of a painting truly brings the object to life. Perhaps the most obvious case for this is when encountering modern canvas prints, or even studio copies of famous paintings – their flatness can land them somewhere in the uncanny valley, if not immediately signifying their less-than status.

Van Gogh's 1889 Sunflowers and detail showing the thick brush strokes of paint.

Vincent Van Gogh. Sunflowers. Oil on Canvas. August 1889. Van Gogh Museum, Amsterdam.  Right, Detail of heavily textured oil paint.
Rembrandt van Rijn Portrait of a Man with Arms Akimbo, an example of thickly piled lead white paint. Rembrandt van Rijn. Portrait of a Man with Arms Akimbo. Oil on Canvas. 1658. Agnes Etherington Art Gallery, Kingston, ontario. A local treasure and example of how lead white paint was used to create textured paint surfaces.

Unlike acrylic, the rheology of oil paint is heavily, if not exclusively determined by the pigment choice and its concentration in the paint. Lead white is probably the most famous colour for its unique properties in oil paint. The resulting paint is high viscous but also thixotropic. Another rheological superstar term, thixotropy is often used to describe a thick paint that becomes more fluid with agitation, but quickly regains any of its gel-like structure when at rest again. Although this too may sound esoteric, the thixotropic quality of lead white paint was deeply coveted – it gave artists a thickly bodied paint that need not be thinned by oil or solvent to make fluid, instead it responded effortlessly to the touch of a brush, while retaining form and brushwork.

Throughout the 18th and 19th century thixotropic paint mediums were also highly prized. Under the influence of experimental painters like Joshua Reynolds and J.M.W. Turner, thixotropic mixtures of lead dryers, oil and resin called megilps were popular. [ii] These gelled mediums gave an immediately bodied texture, flow and transparency to brushwork in oil paints. They found extensive use in creating thickly bodied glaze layers that previous could only have been thin veils of colour.

Dort or Dordrecht: The Dort packet-boat from Rotterdam becalmed

JMW Turner. Dort or Dordrecht: The Dort packet-boat from Rotterdam Becalmed. Oil on Canvas. 1818. Yale Center for British Art. Artists like JMW Turner and Joshua Reynolds are well known to have modified their oil paint rheology with mediums like megilps.

Oil paints unfortunately have a complex chemistry of drying, aging and degradation that is readily disrupted by the inclusion of additional media in the quest for modified rheology. The consequence of megilps were quickly apparent with many works deteriorating within years of their completion. Paint layers darkened, cracked and fell off canvases. Adding further insult to injury, heat treatments intended stabilize flaking paint squashed any traces of the brushwork the artist intended to build. The effects were so disastrous for artists like Reynolds that an exhibition of his deteriorated works was staged with the sole goal of dissuading contemporary artists from further using megilps and the likes of.[iii] By the end of the 19th century, however, painting would take on a new direction that meant a fall from popularity for these problematic mediums.

“…cold and often without feeling.” The History of Early Acrylic Paints

After the late 19th century Impressionists further explored the representation of reality through light, colour and texture, artists of the 20th century began exploring more overt abstraction, colour, composition, and flatness in painting.

In the 1940s, painters like Morris Louis were looking for colourful and liquid paint to create their design focused composition and abstract works. Experimental artists like Picasso had pioneered the use of commercial house paints, like Ripolin, in the previous decade. Commercial house paints offered an economical, pre-formulated source for liquid paint, but with several caveats – they offered a limited range of colour and were greatly lacking quality when compared to artist’s oils. Commercial house paints are made with a mixture of opaque pigments and fillers engineered to give coverage and mass tone as the paint is supplied. The pigments are often poorly dispersed and historically of less than archival quality. The resulting paint would be difficult to mix with, creating a tendency toward a muddy palette. This perhaps informed Picasso’s own colour choices for much of his Cubist period.

Picasso's girl with a mandolin, an example of early use of house paint in fine art painting

Pablo Picasso, Girl with a Mandolin (Fanny Tellier). Oil on canvas. 1910. Museum of Modern Art, New York. Picasso is credited as first fine artist to adopt fluid, flat-dryng house paints

In attempts to make their own colourful, liquid paint, artists like Louis would heavily thin artist’s oil paints. The results were mixed – the excessive amount of solvent necessary to liquify artist’s oils meant the resulting solution was weak in pigment and prone to separation. In works by Helen Frankenthaler, we can see the deleterious effects of overly thinned oil poured onto raw, unprimed canvas: a halo of discoloured oil has separated from the paint where it was applied. Additionally, oil is well known to accelerate the deterioration of canvas due to high acid content, making these works likely unstable for the long term.[iv]

The first acrylic paint for artists was developed in the late 1940s, in part to address the lack of fluid alternatives to artist’s oil paint. Magna® was invented by Leonard Bocour and Samuel Golden in conjunction with Rohm and Haas, the principle manufacturer of acrylic resins then, and to this day. Leonard Boccour “wanted something with viscosity, something that could simulate oil and they thought in terms of house paint, something that was very loose and liquidy and very, very flat.” Magna® was advertised as a fast drying, flexible alternative to oils. Its very high pigment concentration allowed the paint to be thinned while keep intense saturation for staining and pouring. Magna® was hugely influential on the artists of North America and later the UK. For Louis, Magna® was critical for achieving his thin veils of colour and intense stains. These effects could not be produced by traditional oil paint or wall paint. [v]

magna solvent acrylic paints

Magna® Solvent Acrylic paints. Image by Seventex via Wikipedia. CC 3.0. Magna® was the first artists’ solvent acrylic paint available.

Despite its breakthrough technology, Magna® was not without problems. The paint required users to work with large amounts of solvent (Louis was known to use four gallons for a painting), the paint could be resolubilized and disturbed by the application of further layers, and over thinning of the paint resulted in cracking and separation on the canvas. [vi]

Henry Levinson, founder of Permanent Pigments was one of the first to see the advantages of using water-based acrylic emulsion for artist’s paints – it could be thinned with just water, and could be layered with the same paint once it was dry. In 1955 he developed one of the first artist’s acrylic emulsion paints, Liquitex®. Other manufacturers quickly followed suit. Accounts of these early acrylic paints note it was thin, runny, and not generally commercially successful. Frankenthaler described it as “often very cold and often without feeling.” However, for many painters of the mid-20th century, the rheology of this paint became intrinsically linked to their expression as an artist. Modern painters felt that a flat surface, devoid of brush marks was impersonal, but also critical to their practices. A lack of texture highlighted their contemporary use of colour and composition – rather than referencing the grand tradition of oil painting, optical effects, and representation.  Andy Warhol felt very strongly about this surface quality, seeking uniformity, devoid of artistic intention in his repetitious pop-art works like the now famous Marilyn Diptych (made with layers of oil-based silkscreen and hand paint acrylic emulsion paint). A quote from Patrick Caufield summarizes the feelings of the era, “I’m not asking for brushstrokes. I haven’t got any brushstrokes, you know; I’m not Rembrandt.” [vii]

Instead of thixotropy, the terminology of these paints revolves around utilitarian properties like sag resistance.[viii] Wall paint is designed to become fluid as it is stirred and shaken, but gel upon rest, creating drip-free formulations for brushing and rolling vertical surfaces. This was balanced with self-leveling properties to given flat, even coatings – those with long rheology that are able to slightly flow under the force of gravity alone, but not completely flow off the wall.[ix] The same technology was used to formulate the earliest artists’ acrylic paint, resulting in similar properties – flat, even surfaces.

Acrylic paint with oil-like viscosity and gel mediums were eventually introduced in the 1960s by several manufactures, but were of similar quality to earlier liquid acrylics. Despite being thick, these paints had long, stringy rheology that slumped and flowed as they dried. Additionally, painters still trying to heavily thin their paints, now with water, still encountered the same issues as overly thinned Magna®, with cracking and pigment separation. [x] Acrylic as we know it today was still in its infancy.

Contemporary Chemistry: Formulating Modern Acrylic Rheology

Water-based acrylics have come a long way since their advent in the 1950s. Once dismissed as too thin or glue-like paint, acrylic is now versatile enough to replace nearly every other artist’s medium. Tri-Art considers acrylic paint to be the great imitator of everything – it has an amazing capacity to replace artists’ materials historically made from a range of oils, resin and solvents. It is largely by modifying acrylic’s viscosity and rheology that this medium is able to shape shift into such a wide range of artists materials. Manufacturers like Tri-Art produce not only acrylic paints, but also a range of inks, screen printing media and pouring fluids.

inks on a brush and a nibimage of acrylic based screen printing ink being poured onto printing screen

Acrylic is the great imitator of all things. More than just paint,  Tri-Art produces inks and screen printing mediums. Creating the proper viscosity and rheology allows acrylic to morph into this spectrum of possible materials.

Because of their watery, primal state, all acrylic products are created with the aid of rheological modifiers. The three main types are celluloses, polyacrylates, and associative thickeners. Cellulose thickeners are the oldest thickeners available. These are chemically modified cellulose polymers that gel the water component of paint to give it body, but also thin with mixing and brushing. This property, called shear-thinning, gives paint good brushing qualities and cuts down on splattering while rolling. Cellulose thickened paints have long, stringy rheology that result in self-leveling properties that are often exploited in wall paints and gessoes. Polyacrylates thickeners, in contrast, form firm gels with short rheology. Many of us will be familiar with these gelling agents as Carbopol, the agent used to give body to hand sanitizer and many other personal care products. The last category, associative thickeners, consist of a wide range of small molecules that create bridges between the paint components. Rather than greatly thicken the acrylic paint, associative thickeners can be utilized to stabilize the pigment content, while still allowing for flow and leveling properties. Often these thickeners are thixotropic in nature, keeping pigment suspended in a thickened matrix, but readily thinning out upon shaking and brushing.[xi] By selecting amongst these rheological agents and other components, modern acrylic paint and mediums can be engineered to encompass a wide range of properties that solve the issues faced by artists of the past.

Fine Art Philosophy for the Mass Market Medium: Tri-Art Acrylics

At Tri-Art, our acrylics were developed with a deep appreciation for the hand of the artist. When developing Tri-Art’s acrylic, it was imperative that the paint had excellent handling, with a short rheology that could match that of oil paint. Unlike existing acrylics, Tri-Art didn’t want to develop an artist paint using the principles of house paint formulation. Tri-Art wanted to make something that was like oil paint, but with endless possibilities of acrylic. Many other acrylic brands still utilize thickeners that result in paint that is heavily bodied and viscous, but also stringy and glue-like paint that loses resolution as it dries. With Tri-Art acrylics, the short rheology yields a paint that effortlessly moves but also holds a crisp record of your brushwork after drying. This includes not only our Finest Quality High Viscosity line, but virtually all our acrylic paints.

sharp peaks of high viscosity red acrylic paint illustrating the very short rheology

The sharp, high-fidelity peaks of Tri-Art’s Finest High Viscosity acrylic paint hold a record of your mark making, even after drying. Our commitment to quality means that you can sculpt tall peaks of paint onto the canvas without worrying it will fall off.

Unlike the disastrous experiments medium use in oil painting, or the early experiments of overly thinned acrylics, todays contemporary acrylic paints offer artist the ability to explore further with confidence. Beyond mere colour, understanding the rheology of acrylic paint can truly help you to achieve the paint surfaces you envision. For those who wish to paint with body, Tri-Art offers high viscosity paints and mediums. For those who wish to paint with fluidity, Tri-Art offers low viscosity paints, along with liquid glass pouring mediums, self-leveling gels and more. With a selection of these paints and mediums you can create, or recreate, a nearly infinite range of surface textures and effects.

For a masterclass in acrylic painting and mediums consider reading Rheni Tauchid’s Acrylic Painting Mediums and Methods[xii], or New Acrylics Essential Sourcebook[xiii].

gel medium in jar.

Notes:

[i] Daniel Blair, ‘Viscoelastic Properties: The Rheology of Soft Solids’, in Molecular Gels: Structure and Dynamics (Cambridge: Royal Society of Chemistry, 2018), pp. 28–56 <https://doi.org/10.1039/9781788013147-00028>.

[ii] Leslie Carlyle, ‘Building Visual Evidence of Past Practices in the Creation of Oil Paintings’, in A Changing Art: Nineteenth-Century Painting Practice and Conservation, ed. by Nicola Costaras and others (London: Archetype Publications Ltd., London, United Kingdom, 2017), p. pp.23-36, 11 figs. (9 color), 8 notes, refs.

[iii] Carlyle.

[iv] Jo. Crook and Tom. Learner, ‘The Impact of Modern Paints’ (New York: Watson-Guptill, 2000), p. 192 p. <file://catalog.hathitrust.org/Record/004084627>.

[v] Crook and Learner.

[vi] Crook and Learner.

[vii] Crook and Learner.

[viii] ‘Rheology and Interfacial Measurements for Coatings, Paints and Inks’, Center for Industrial Rheology <https://www.rheologylab.com/articles/coatings-paints-inks/> [accessed 8 March 2021].

[ix] Adrian Hill, ‘Rheology for Coatings’, Paint and Coatings Industry, 22.3 (2006), 52–57.

[x] Crook and Learner.

[xi] ‘Rheology Modifiers Selection for Paints & Coatings’, SpecialChem <https://coatings.specialchem.com/selection-guide/rheology-modifiers-selection-for-waterborne-and-solventborne-coatings> [accessed 9 March 2021].

[xii] Rheni Tauchid, Acrylic Painting Mediums & Methods : A Contemporary Guide to Materials, Techniques, and Applications Acrylic Painting Mediums and Methods, First edit (New York, New York: Monacelli Studio, 2018).

[xiii] Rheni Tauchid, New Acrylics Essential Sourcebook : Materials, Techniques, and Contemporary Applications for Today’s Artist  (New York: Watson-Guptill Publications, 2009).

Bibliography

Blair, Daniel, ‘Viscoelastic Properties: The Rheology of Soft Solids’, in Molecular Gels: Structure and Dynamics (Cambridge: Royal Society of Chemistry, 2018), pp. 28–56 <https://doi.org/10.1039/9781788013147-00028>

Carlyle, Leslie, ‘Building Visual Evidence of Past Practices in the Creation of Oil Paintings’, in A Changing Art: Nineteenth-Century Painting Practice and Conservation, ed. by Nicola Costaras, Kate Lowry, Helen Glanville, Pippa Balch, Victoria Sutcliffe, and Polly Saltmarsh (London: Archetype Publications Ltd., London, United Kingdom, 2017), p. pp.23-36, 11 figs. (9 color), 8 notes, refs.

Crook, Jo., and Tom. Learner, ‘The Impact of Modern Paints’ (New York: Watson-Guptill, 2000), p. 192 p. <file://catalog.hathitrust.org/Record/004084627>

Hill, Adrian, ‘Rheology for Coatings’, Paint and Coatings Industry, 22.3 (2006), 52–57

‘Rheology and Interfacial Measurements for Coatings, Paints and Inks’, Center for Industrial Rheology <https://www.rheologylab.com/articles/coatings-paints-inks/> [accessed 8 March 2021]

‘Rheology Modifiers Selection for Paints & Coatings’, SpecialChem <https://coatings.specialchem.com/selection-guide/rheology-modifiers-selection-for-waterborne-and-solventborne-coatings> [accessed 9 March 2021]

Tauchid, Rheni, Acrylic Painting Mediums & Methods: A Contemporary Guide to Materials, Techniques, and Applications Acrylic Painting Mediums and Methods, First edit (New York, New York: Monacelli Studio, 2018)

———, New Acrylics Essential Sourcebook: Materials, Techniques, and Contemporary Applications for Today’s Artist  (New York: Watson-Guptill Publications, 2009)