Page 7 - Mediums
Painting mediums are used to modify the rate of drying, increase gloss, improve flow or add texture, mediums as an additive to color. Working with oils, solvents, mediums, and varnishes for painting requires an in-depth understanding of paint. The wide range of oils, mediums, and solvents to control color makes choices difficult.
Many vegetable drying oils have been available to the coatings industry for nearly a century. Still, they have not been made available to artists working on oil painting or, in many cases, are mainly unknown to artists today. This may be due to the lack of information published about these oils in artists' manuals and not taught in art schools. This article introduces the many different drying oils (in this case, these are all derived from flaxseed) available to the industry and now to artists through Natural Pigments.
An interesting reference in a manual regarding the drying properties of oil paint has some application to oil painters. Some of the information is outdated and inaccurate, yet it does provide an easy-to-understand explanation of drying properties. I have edited some of the content to make it more applicable to artists.
Black oil is the classic drying oil made with lead. It improves the handling and drying of oils and can be used in recipes to make megilp, Maroger, and Roberson's mediums and traditional oil varnishes, such as copal. This is the classic drying oil made with litharge (lead oxide). Since the earliest times, litharge was cooked with vegetable oil, such as linseed or walnut oil, to clarify it while removing impurities and imparting faster drying characteristics. Cooking the oil for long periods and at high temperatures allows more significant amounts of litharge to be dissolved in the oil while at the same time darkening the oil.
Did watercolorists of the 18th and 19th centuries use mediums to brush and manipulate their watercolors? The evidence shows that they handled their colors differently from contemporary artists today. Here are some historical references on the use of watercolor mediums by British watercolorists of the 18th and 19th centuries.
No paint is known to keep its original color indefinitely. From the moment it is applied, it starts changing color. The only issue is, therefore, the degree to which this color change will take place. The oils and resins used by artists tend to yellow or discolor upon drying and aging. Since oxidation and polymerization are the main actions during this process, we can more or less assume that the oxidized and polymerized molecules are darker in color than the original molecules, and these give yellowing or poor color retention.
There’s a bewildering array of drying oils for oil painting. Where do all the different drying oils come from? How are they different? And how do you choose the right one for your painting?
