Technical Explanation of a Painting

This article references the website I worked on from 2002-2022 about painting and painting materials, now available as a mirror thanks to Philippe Masson. The context of the painting is a series in a similar style that is documented in chronological order on this page of the website. More information about the medium process of these paintings is here. Finally, an overview of what I learned about the materials and process by comparing modern technique with the results of contemporary technical art history and conservation science is available in the book Living Craft, available as a free PDF here.

Taking the website down in 2022 took a while to come to terms with. For two decades, I had posted paintings, information about handmade painting materials based on research into older practice, and news about the developing materials process. This had been fun for a long time, but after twenty years I felt I had done what I could do, and that the work needed to stop being on the increasingly fast, yet decreasingly coherent, stage of the internet. A few years before, I’d switched from realism back to abstraction, (which, at that point, felt, if did not appear, to be more real) and this was a good step, but not enough. Stopping was good for me because the exposure, minimal though it was, had become distracting and occasionally invasive. In answering email questions, I often felt like the prisoner of expectations that had little to do with handmade materials, more with the perennial search for technical shortcuts. I was also inevitably involved in a complex relationship with the mainstream art supply cabal, since the technical tack I had taken went another direction, and had been documented so extensively in Living Craft, and I had somewhat accidentally exposed a pervasive fraud regarding various chemical concoctions being sold as natural spike lavender essential oil. (This fraud, of course, goes on, it is quite a fat cash cow. Only spike lavender sold by reputable essential oil dealers is real.) Finally putting all of this behind me was a great relief. In this context, stopping was good for the work in that I no longer compelled to make an acceptable product, or follow the rules, including my own.

The painting above (23x25.5 cm, tempera grass on gessoed paper) occurred later in October, 2022, a few weeks after I took the website down. This was the third painting in a series that began using a combination of two materials I was interested in that used resins. The use of resin in oil paint tends to be a short term plus in terms of the paint’s gloss and internal glow, and for this reason various resins were the most popular ’lost secret’ of the 19th century writers. Yet, technical art history and conservation have now established that resins introduce long term darkening to at least some extent, and, more importantly, that resins dissolved in solvent (spirit varnishes) also produce a much weaker paint film over time because the resin remains a separate component, with different reactions to heat and humidity, than the increasingly brittle polymerized oil film. With hard resin varnishes (resin dissolved in oil using heat) the issue is the darkening potential, so it is a question of using a small amount, an issue which is also involved with the colour scheme of the painting. The abstract work was involved with relatively bright colour. I found the brightest colour in oil to be in a lean emulsion medium that used egg yolk, but over time this actually felt too bright and too related to the many forms of yolk-based tempera grassa that have been made over the centuries. While I had made the hard resin varnishes (amber, copal, sandarac) in 2006-08, the only resin I was using regularly in the work at this point was about 5% fused damar, damar resin dissolved at a low temperature in oil, not solvent.

The craft had taught me that there was far more to all the materials than the way they were typically used in modern practice. It was a question of investigating further, which usually meant expanding the frame of reference to include working with the raw materials themselves. So, while experience had made me very cautious about resins, my feeling was that there was far more to explore with the resin situation. The first material was based on something I’d used off and on since noticing in 2006 that a hard resin (in the original case, amber) releases its thixotropic component long before it goes into solution in oil. Specifically, at the point in the heating process when the ground resin rises to the top of the oil. This ’amber oil’, especially as it thickened over time, could be used in small amounts to make a given medium quite thixotropic. It seemed reasonable that Manila copal resin, being quite thixotropic in oil and melting at a far lower temperature than amber, would make a similar oil but in a simpler way, thus giving the working quality of a hard resin varnish to the medium or paint with less potential for darkening. I first tried 10 g ground Manila copal resin heated in 50 ml preheated walnut oil until the resin floated, a little more than an hour at 150C.

This material, called protocopal, was at first mid-orange but became straw-coloured quickly as it thickened. (At the time of this painting, it was not quite the thixotropic taffy pictured here, but still introduced thixotropy.) So this was a way to create a thixotropic material in the studio. I had made Manila copal varnish earlier, and really enjoyed working with it, but this must be done outdoors, and inevitably involves lots of smoke at the end.

It is probably a good idea to discuss copal varnish itself. There are many types of copal resin with different degrees of age and hardness worldwide, so copal varnish is capable of being many things. This material was used a great deal in the 19th century and some copal varnish production continued into the early 20th century. Copal varnish has accumulated lots of conservation caution due to darkening and difficulty of removal as a final varnish. But the copal varnish used in painting in the 19th century was the very specific type made for horse-drawn carriage trade. This varnish was convenient for painters, but not ideal for painting because its manufacture involved cooking relatively low quality linseed oil at high temperature for many hours, as well as the use of the period driers lead and manganese. In this approach there are three factors that create strong long term darkening: low quality linseed oil, very high heat for many hours to first polymerize the oil, then fuse very hard copals, and the driers themselves.

The only copal ever manufactured specifically for painters was made by Permanent Pigments from the early 1940s through the mid 1970s according to the formula of painter, teacher, and technical writer Frederic Taubes. This varnish became well-known enough to be noted in Dali’s book ’Fifty secrets of Magical Craftsmanship’ published in 1948.

Details of the composition of the Taubes copal remains unknown, although a technical description by Permanent Pigments suggests it was made with resin and oil only, the colour and thixotropy in Taubes own work suggest the resins were Manila copal or Pontianac copal. A recent image search suggests that copal varnish made with a relatively simple recipe is experiencing a slow if expensive resurgence, though is still not marketed for painting. (Note that dental copal varnish is made from Manila copal and ethanol. Manila copal dissolved in alcohol is useful as a shellac replacement, but not in the painting process itself.) In any case, resin and oil only was the approach I took in making the varnish in 2006, and it has darkened minimally in two decades since then. Note that the example shown was made with very cool colour and a great deal of this varnish in the paint to establish early on how much it would yellow.)

The second material was varnish made from the resin of Hymenaea Courbaril, a quite amazing tree that is native to Brazil, and called Jatopa there. This resin was imported to Europe by the Portuguese, who first settled in Brazil in 1532. The fresh resin could be dissolved in turpentine, and may have found use as a spirit varnish for furniture or musical instruments. The aged resin was dissolved in oil using heat, and is mentioned positively by Merimee as Gum Anime in his early 19th century book on methods and materials. After this it disappears in literature, and the varnish has not been made commercially for painting to my knowledge, although it was made into a commercial varnish in Brazil later in the 1940s. This resin was interesting it had a low melting point, but not as low as damar, and because it was a species of locust, not a species of pine, such as damar, Canada Balsam, etcetera, all of whose resins yellow over time. I’d stopped using any form of balsam or spirit varnish, but had worked with fused damar in the putty medium for about a decade, and found it worked well in small amounts to sequester the paint film from lowering in tone due to humidity. For more on fused damar, see Living Craft sections 6.7.1.1 and 6.10.1.1.

Hymenaea courbaril is also sold as an incense, smelling somewhat like a toasted cinnamon bun when burned. However, this a commercial track featuring much sharp practice, and the resin I got first turned out to be the Shorea species of damar. I could not find the fresh resin, but the aged resin from Apothecary’s Garden on Etsy was genuine. It was hard, orange, and covered with white oxidation. I washed this off, which may or may not have been a good idea. The resin dissolved in walnut oil at about 150C, meaning it could be made in the studio without creating smoke.

It was very different than copal, in that, even making the varnish at one part resin to one part oil, it was only moderately thick and, when added to the paint, cancelled, rather than enhanced, thixotropy. Also, since the aged resin is used as an incense, this varnish had an engaging smell. I wanted at least some thixotropy for this style, so ended up mixing this varnish one to one with protocopal for the medium.

This produced a balance of their properties: thixotropy from the protocopal, but within the fine working quality of the hymenaea varnish. These materials were added in small amounts to the basic medium I was working with at the time, a putty of marble dust and lean oil mixed one to one with a material I called o-starch: a water-phase mixture of thick wheat starch gel, egg white, and a little walnut oil that was heated first to help the materials interact, then kept in the refrigerator to produce more ductile working qualities over time.

The raison d’etre of this medium is the ternary reaction between starch, protein, and oil that is much studied in food chemistry, but also happens to create a material that is more stable and water resistant than these materials would be if simply mixed and used the same day.

(My thanks to Dr. Roland Greimers for this, and many other explanations and illustrations from the scientific perspective over the years.) I’m still working with o-starch, which keeps indefinitely in the fridge, just adjusting proportions of small amounts of various other ingredients in and out of it for different paintings. I don’t see it as ’better’ than egg yolk as a sequestering tempera grassa ingredient, just one whose gestalt of final appearances is more appealing.

The first two small paintings made with this combination were very different because the hymenaea varnish trumped the broader working qualities of the starch and putty. I thought it was a small amount, but, looking back through the notes, it really wasn’t given the strength of any resin-in-oil varnish. These paintings featured a very fine relief structure and a gentle but deep saturation. It was an intriguing change, and while I liked both the protocopal and the hymenaea varnish as materials, the results weren’t quite what I wanted to see, the paint was too facile or ingratiating. As is often the case when changing a formula, the change went too far. So, for the painting pictured here, I kept the protocopal, but went back to a smaller amount of a fused damar medium instead of the stronger hymenaea varnish. (The work can of course be made without these materials, just using the basic medium of the lean putty 1:1 with o-starch, and either dry pigments in water, or tubed oil paint. These paintings dry matte, and very brightly, with a noticeable internal texture using dry pigment, but are also quite unsaturated until they are given a thin final coat of a non-yellowing oil about a year after they’re made. At first I wanted to know which was better: saturation in the paint, or saturation after the paint, but now it seems they are different but equally valid approaches.)

The painting here began with an underlayer sketch in Trans Mars Yellow Oxide, a very traditional way to start, then went further into several variations on a somewhat muted orange. The paint set well enough that translucent layers of the other colours were then added, with the shapes using white added when it had set further the second day. (A feature of the medium is that the water-phase component sets quickly, allowing carving or removal for at least for another day, while the oil itself takes a few more days to fully dry.) As a result, the emphasis on the difference of the various components of many paintings in this series, often resulting in an inherent energy or jumpiness, is diminished by an overall unity. I remember being fascinated by this for days afterwards because it was so different that the others in the series. It was like finding out the person I thought of as me was only part of the story. This painting seemed like the beginning of something new in a way that was a surprise. And it was, but not in the way I imagined. For some reason, this was not the beginning of a new set of paintings based on this more unified approach, but the last painting to be completed in this series to date. Before this time, paintings in this series reached completion sporadically, but regularly, typically through an alla prima approach. After this time, none have so far. Interesting things have happened, graphically, with colour, and with the materials, but nothing feels finished. This may be a natural consequence of the work leaving the internet after having been on public display for so long, or of something even newer wanting to happen next. So, this one was the capstone of that pyramid, and after that, nothing further could be added without beginning over.

This has happened before, so doing so again is familiar. It is even a relief to be a beginner again, exploring what wants to be explored simply for its own sake. Although the last eighteen months have been a long winter for the work, they’ve expanded frame of reference about it a great deal. This has helped appreciate this work as a group more, rather than seeing the paintings as stepping stones to what might happen next. While in this process from 2019 to 2022, I became so fascinated by how much it offered in terms of learning about the endless interactions of the creative triad of colour, form, and handmade materials, that I didn’t appreciate the process, or its results, as much as is possible now. As with winter itself, there is a kind of peace or redemption in a prolonged pause, a more accurate assessment of what actually happened and why. Still, being human, I cannot help but wonder what is going to happen next.