Oil Paint Chemistry
Getting ready to make oil paint. A range of oils will be used to bind the raw pigment to make paints.
“The chemistry of the drying of the linseed oil is so complex as to be unintelligible
to anyone who is not a student of chemistry.”
A World of Complexity
Oil Paint Chemistry. Three simple words that have worlds upon worlds of complexity contained within them— and to my surprise the door to that world seemed to be mysteriously locked, meaning that it was not at all obvious where to find a book on the subject or a class.
About two years ago, I began to search in earnest for a chemical understanding of oil paint. After exhausting the usual channels I turned to forums and received a few interesting replies from technical specialists.
What I found was a great surprise: linseed oil, the ingredient most commonly used to make oil paint, is an exceedingly complex substance— so much so, that it still holds mystery for those scientists who specialize in its study.
In the last month or so, I took an specialized course on painting materials called the Painting Best Practices Workshop by George O’Hanlon and his team at Natural Pigments. The course shed more light on the chemistry of oil paint materials than anything I’d been able to find so far, and greatly enriched my understanding of archival painting materials. The course was a six-session class taught by the technical director of Natural Pigments, George O’Hanlon.
Why Is This Information So Hard to Find?
Feuds, Legends and Lore
As painters, there is a lot of lore to sift through when it comes to how our materials work, and even the books on the subject quickly become dated and many resources are full of misinformation. For example, many books on materials will go through six editions through an author’s lifetime, and then, when the author passes away, no further updates are made to reflect the current state of the field. Famous names in this field that come to mind are Ralph Mayer and Mark Gottsegen. There are also rumors of author feuds, where books written in the same era contradict each other. It is exceedingly difficult for an artist to weigh all of this information and sort out truth from dated truth, or truth from dreams.
Lost Histories
Even the books on the use of artists’ materials do not often delve into a broader discussion of their material properties. The best book I have found on this subject so far is Kurt Wehlte’s The Materials and Techniques of Painting, with a supplement on Color Theory. While dated, this book contains some broad-level information on how to think about solvents, oils, waxes and resins.
While not strictly related to chemistry, Wehlte describes details about the growing of linseed oil, which has parallels to wine in that the exact conditions of its cultivation affect its qualities. He also describes the shortages that occurred in Europe after World War II, specifically surrounding the unavailability of walnuts. He waxes eloquent about a mysterious cultivar of sunflower whose oil made the most fabulous paints— but the knowledge of the sunflower variety, its oil, and the paints that were made from it were all lost to history.
Technical Experts Weigh In
My search lead me to a post on a message board, where I heard from Sarah Sands, senior Technical Expert for Golden Artist Colors and Williamsburg Oils. Sarah recommended a handful of resources. For those interested I’ll include links to them here:
Organic Chemistry of Museum Objects, 2nd ed. by Mills and White
Science for Conservators Series, Vol. 1 on Materials, and
Analytical Chemical Studies on Linseed Oil Paints, by J.D.J. Van den Berg
The latest step in this journey has been the class with the Technical Director of Natural Pigments, George O’Hanlon, called Painting Best Practices. I knew I had wanted to learn about how to make my work more archival. What I was not expecting is that more than any other single resource it was the most informative when it came to developing and understanding of the chemistry of oil painting.
The class covers grounds and sizes, pigments and binders, optics, how to make oil paint, and studio safety. Regarding chemistry, we did not get into chemical equations, but a thorough analysis was offered for each of the various elements that comprise a painting and the way the age together as a system. Their chemical and physical interactions were explored in-depth from the perspective of conservation science. It is a body of knowledge that would benefit every professional painter.
More on this, and the highlights from the class, to come!