One of the most frequently asked questions about encaustic painting is “What is the right surface to paint on?” The mechanics of adhesion in oil and acrylic are well established but there is no equally standard body of knowledge about the adhesion of encaustic to various surfaces.
In 2008, when we worked with the chemists who helped us develop our Encaustic Gesso, it was necessary to test its performance. We needed to know how well the gesso adhered to a panel and how well encaustic paint would adhere to the gesso. This became all the more crucial when we partnered with Ampersand Art Supply to create a machine-made panel based on our Encaustic Gesso. Encausticbord™ had to be both durable and seductively inviting to work on. It was also important that it would be suitable for multi-media use since encaustic is so often used in conjunction with other mediums and materials.
Once it was clear that the Encausticbord™ worked well with oil, water, and wax based mediums, we applied a series of systematic tests for durability that we had used when we released our brushable Encaustic Gesso.
The first and simplest test, of course, is to freeze a painted panel and then slam it to see if the paint will break off. We have been using “The Freezer Test” since the early nineties when we needed a simple way to help artists determine compatibility of their substrate with encaustic. This mainly tells you how well the painting should hold up under acute impact when shipped in cold weather.
The longevity of a painting however, depends on many variables, the most important of which are the gradual fluctuations in temperature and humidity that take place over long periods of time in normal conditions for exhibiting or storing artwork.
To simulate this, we have developed a procedure of cycling painted panels through freezing and thawing periods to exaggerate those fluctuations in temperature. We follow this with quantifiable stress tests designed to detach any areas of paint that became vulnerable from the repeated contraction and expansion of the freezer test.
We repeat these tests using a range of colors, because, as most of you who work in encaustic know, every pigment has a characteristic effect on the wax (as it does on other mediums). Umbers, for example make the wax very hard and brittle. Cadmiums make it soft. Titanium white can make it gummy. Each family of colors has to pass the test for a ground to be considered suitable for encaustic.
How dependable are these tests? It’s fairly easy to say if you’re talking about a couple of decades. Most of us have experienced how materials behave in that amount of time. We know from the Fayum portraits that beeswax will last 2 millennia and longer. Yet our modern pigments differ from the ancient ones. The supports and grounds we work on are also different. This is why it is important to continue developing tests to simulate fluctuations in the environment over time. It is important to test the effects of temperature, humidity, light, vibrations, pollution, and phases of aging in the medium that over time can break down the structure of the paint and cause the separation of one material from another.
The methods used in these tests do not result in predictions, only educated guesses. What they can do is separate materials with short-term durability from those that promise to survive much longer.
One last word about shipping in cold weather: Most artwork is fragile in extreme cold, even work that is made with materials that easily withstand normal temperature fluctuation. The best precaution in any instance is careful packaging and, when feasible, expedited shipping time.