Choosing the Right Solvent

Just when or maybe because oil painting has lost its cache as “primary media,”  young painters are intrigued by the myths and tall tales of bygone days. Simultaneously they seem under educated about studio practices before the Industrial Revolution.  

For decades, artists have not been trained how to use oil painting materials and techniques in 80% of America’s art schools and colleges. I remember when the EPA issued citations and fines to art schools for mishandling of toxic waste like turpentine about 30 years ago. The Rhode Island School of Design improved their oil painting program when most schools simply banned the use of solvent.  

Oils, acrylics, pastels, watercolor and other art media are made from the same basic pigments.  Managing artists’ colors using multiple media is not as difficult as managing binders.  Previously artists did not have so many ways to bind pigments.  Until the invention of European style oil painting about the 14th century, master painters could choose tempera, fresco or mosaic.  

ACMIHedpaschke Amber man 99.jpeg

What is revolutionary about adding linseed oil as a binder is transparency added to the painting process.  Historically, raw linseed oil had been prepared for industrial varnishes by boiling it with various natural resins like copal and mastic.  Refined linseed oil was used for medicine and in cooking. The quality used in medicine was probably more aromatic but similar to the cold pressed linseed oil you can buy from health food stores today, probably just as expensive. 

It would not take long for the experimental painters of the era to see film failure if their paint layers were too fat. Adding the correct measure of solvent increases cohesion because solvent defats the oil just so a layer of color can “bite” into the layer beneath. As history has demonstrated these materials when combined correctly make strong paint films. And the process captures light deep inside multiple paint layers.  As the light struggles to be released, the painting surfaces glow.    

Since the 14th century mixtures of solvent/oil were common mediums. The oil to solvent ratio can be adjusted between layers (fat over lean). If there are any secret recipes from the Old Masters, these must be the ratios between oil/solvent + pigments used to create unusual surface effects!  Very tricky to find the balance.  

Unlike contemporary media, oil painting materials are very simple, very raw materials.  Because colorants + oils + solvent can be combined any way at the will of the artist, mastering this media is technical.  If your plan is to go the art store and buy a bunch of stuff and make an oil painting, rethink your plan. It would be so much easier to buy acrylics painting materials.  Painting in acrylics is true 20th century media.  Art materials manufacturers, especially Golden Artist Colors, have scientific research and technical data to satisfy any painter. 

If you insist on buying a bunch of stuff and painting in oils, start by choosing the right solvent.  

To thin oil binders, the solvent has to be hot enough to reduce the viscosity of oil to make, for example, a glaze layer.  Gamsol and Turpenoid are two brands of ODORLESS MINERAL SPIRITS (OMS) commonly available to painters. Gamsol is just hot enough to dissolve vegetable oils like linseed oil, poppy and safflower oils. OMS is not enough strong to dissolve natural resins like damar and copal.  

To know the solvent power, look at the Permissible Exposure Level (PEL), the higher the PEL, the weaker the solvent. Turpentine is “hot” - PEL of 100.  OMS is less strong - PEL of 300.

Despite the historical, mystical allure of “traditional” oil painting and the siren’s aroma of turpentine, OMS is the only solvent that should be used in oil painting today  

Had painters of the past had access to safer solvents, they would have used them. Throughout art history, innovations were embraced by artists like water-based media has been embraced by artists today. For those intrigued by oil painting, get use to working with OMS rather than a stronger solvent. At Gamblin Artists Colors we use to say:  painters can respect the traditions of the past while facing the future, which is in studios with no or low exposure to solvent.