SOLVENTS, DRYING OILS, RESINS AND MEDIUM

SOLVENTS
Solvents are added to oil paints for temporary change; they are designed to work in a way such that they evaporate consistently and completely as the oil paint dries. (The correct technical term is diluents, as not all are solvents, but it's not a commonly used term.) Solvents are also used to soften resins, to make mediums, for cleaning up, and for cleaning brushes. Solvents are flammable and their fumes can be noxious. Hence, it is very important to use solvents in a well-ventilated room.

Turpentine is the traditional solvent used in the oil painting. It a tree resin and has a very fast evaporation rate; it also releases harmful vapors and can absorbed through healthy skin. Try using only artist quality turpentine, which is colorless, like water. The industrial variety found in hardware stores is usually tinted and probably contains impurities. Artist quality turpentine is also known as spirit of turpentine, oil of turpentine, genuine turpentine, English turpentine, distilled turpentine, double rectified turpentine, or even simply turps. For any recipes containing damar, turpentine is the most appropriate solvent. The gummy residue of turpentine left after evaporation is harmless, though turpentine is best when its fresh. See chart below for toxicity rating and warning.

Mineral spirits is made from pure petroleum and has a moderate evaporation rat; it does release harmful vapors, but is not absorbed through healthy skin like turpentine. Mineral spirits is less expensive than turpentine; it is a stronger solvent than odorless mineral spirits (which is sometimes called white spirits). Some artist prefer mineral spirits to turpentine because it leaves no gummy residue, does not deteriorate with age, is cheaper and causes no apparent reaction in people sensitive to turpentine. Mineral spirits can used as an oil painting medium in place of turpentine, but not in recipes containing damar, as damar is not completely soluble in it. Mineral spirits can also be used to clean brushes and other tools. See chart below for toxicity rating and warning.

Odorless mineral spirits is made from petroleum, has a reasonable evaporation rate, and cannot be absorbed through healthy skin. It is more expensive than normal mineral spirits due to the added extraction process to remove the fumes. It has the same applications and qualities of the non-odorless mineral spirits. Good brands of mineral spirits include Turpenoid, Thin-ex, and Gamsol. Turpenoid®. See chart below for toxicity rating and warning.

• Mineral spirit is a petroleum distillate that leaves no gummy residue; it is cheaper than turpentine and seems to be less abrasive to those who have reactions to turpentine; it cannot completely dissolve Damar.
• Turpentine is made from pine tree resin; use only pure gum spirit painting mediums as others contain impurities; use this solvent in mediums calling for Damar.
• Citrus Thinner is a by-product of citrus peel liqueur; it can be used as a substitute for mineral spirits; it speeds up drying time.
• Odorless Mineral spirits is a petroleum hydrocarbon; it can be used as substitue for mineral spirits, but cannot be used with damar; it is virtually odorless.
• Turpenoid is an odorless mineral spirit.

Tip: Test the quality of a solvent by putting a little on a drop of paper and to let it evaporate. If it doesn't leave any residue, stain, or smell, it is good enough to use with oil paints.

DRYING OILS: use for gloss and transparency; also used for increasing the flow of paint.
• Linseed Oil adds gloss and transparency to paints; can turn yellow and become brittle with age; only use the refined cold-pressed type only as medium.
• Poppyseed Oil is more transparent and less likely to yellow than linseed oil; it is often used as the vehicle for whites and light colors; it dries slowly and is proned to cracking.
• Safflower oil is a good substitute for linseed oil; though it is less likely to yellow than linseed, it does become brittle over time.
• Stand Oil is a "cooked" version of linseed oil; it cannot be used by itself; it creates an excellent glazing compound when mixed with damar and turpentine.
• Sunflower Oil similar to poppyseed oil; it can be substituted for linseed oil.

RESINS
Resins are used to increase glossiness, reduce color intensity, reduce drying time, and add body to drying oils. The most popular is a natural resin called Damar. When used as a medium, it should be diluted with turpentine as it would not dissolve thoroughly with mineral spirits. It can also be used as a varnish.
• Damar is the natural resin of a tropical fir tree; it dissolves readily in turpentine; it adds gloss and brilliance to the surface of paintings; it can be dissolved by subsequent layers of paint containing turpentine.
• Venice Turpentine is an oleoresin from the larch tree; it adds to the stability of the paint surface and yellows very little over time; it is an excellent resin for painting mediums and has been used for hundreds of years.
• Oleopasto is an alkyd-based synthetic resin intended for impasto use; it adds strength to thick paints.
• Win-Gel is an alkyd-based synthetic which can be used for light impasto; it must be thoroughly mixed into the paint before application.
• Liquin & Daniel Smith are alkyd-based synthetic resins used to increase transparency and brilliance in the paint surface; they reduce drying time; they are not recommended for impasto use.

MEDIUM
Medium is a made up of drying oil, solvent and resin. A good standard medium is a mixture of the three in equal parts, but you can adjust the amount of each depending on your painting needs. If you are allergic to solvents, it is also possible to use only Linseed oil as a medium; clean up with Baby oil, then soap and water.