Page 8 - 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.
The term balsam has been used to designate the resinous exudate from trees of the order Coniferae, which have also been called resin or turpentine. Balsam is a soft, semi-liquid consisting of terpenes associated with bodies of resinous properties. The balsams most used in varnishes or as paint mediums are Larch balsam (a component of Venice turpentine), Strasbourg turpentine, Canada balsam, and copaiba balsam. Balsams flow easily on a surface and give a lustrous, pleasing quality when applied. However, unless a harder resin is mixed with them, they deteriorate quickly. Here are several formulas incorporating balsams...
Congo copal is no longer available commercially (at least as it was available in commerce formerly), because the suppliers have long stopped trading due to strife in Africa since the last quarter of the 20th century. Trade of Congo copal was once controlled by the Belgian government, but as this region of Africa gained independence and the demand for copal resins diminished during the last half of the 20th century, the commerce of Congo copal has all but ceased...
Glycerin (also spelled glycerine and also called glycerol) is a humectant and plasticizer ingredient in commercial watercolors today, but it is not always an ingredient in commercial watercolors. An examination of watercolor paints from the late 18th and early 19th century reveals that glycerin was not a plasticizer and humectant in pan watercolors (called 'cake' colors in that period). For example, Rudolph Ackermann used crystal sugar melted in water as the plasticizer and humectant for many colors. In some cases, the recipes called for vinegar...
What are your thoughts on best practices for oiling out between layers and when the painting is finished? What oil do you suggest? What about varnishing instead...
George O'Hanlon
I find it interesting that anyone today who understands even a fraction about making oil paint would recommend cold-pressed linseed oil for making oil colors. I know it is recommended in some of the artist's manuals, but it seems to me these authors never really understood the reasons why or simply copied what others had told them.
Why do we suppose the Old Masters went through such great lengths to "clean" or process their oils before using it in paint? Simply because they wanted to rid their cold-pressed drying oil of foots and other impurities, which cause problems in the dried paint film, such as yellowing.
Refined oils made by industry today are excellent products, and they do not have the faults of cold-pressed products. For example, I have samples of every type of drying oil (linseed, tung, walnut, sunflower, hempseed, poppy, high linoleic safflower oil, etc.) available in North America (and some from Asia and Europe). I can tell you that there...