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.
Gel painting mediums come in a variety of thicknesses and properties, but their primary purpose is to change the consistency or appearance of paint. Think of gel medium as transparent paint so that when added to oil colors, it diminishes the opacity of the color while helping to maintain its consistency. Gel mediums increase the transparency of oil colors without making the paint more fluid, such as when adding drying oil to increase the transparency of a color. This is advantageous when you want a transparent layer of color without making the paint runny.
Formulas for varnishes and mediums call for measurements that are often confusing for artists. For example, in his formula for a glazing medium, Ralph Mayer calls for a “5-pound cut” of dammar (or damar) varnish. How do you know what is a 5-pound cut?
Formulas for varnishes and mediums call for measurements that are often confusing for artists. For example, in his formula for a glazing medium, Ralph Mayer calls for a “5-pound cut” of dammar (or damar) varnish. This measurement refers to the amount of dry dammar resin with spirits of gum turpentine in a ratio called a “cut,” which refers to the amount of resin in pounds dissolved in a gallon of turpentine. This measurement is simple enough to use when preparing your own varnish, but what if you want to use a commercially-prepared dammar varnish, such as Rublev Colours Dammar Varnish or Neil’s Best Dammar Varnish? How do you know if it is a 5-pound cut?
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?
