Most solvents have common characteristics. They are liquids at room temperature. They are very volatile and produce vapors that can be inhaled or circulated by a ventilation system. Most solvents are flammable liquids, and because of the wide range of potential ingredients in solvents, you should always check the label and/or material safety data sheet for a description of hazards.
But, most importantly to us as oil painters, solvents dissolve oil, grease, and fats effectively. It is this property alone that propels oil painters to use solvents despite the other crude characteristics that we can certainly do without. In fact, solvents created specifically for oil painting are made to zone in on compatibility with oil colors as the good quality of solvents, and reduce the less desirable and hazardous ones.
More specifically, solvents can produce local or systemic (central nervous system) effects in people when vapors are inhaled or when liquids penetrate the skin. They are irritating to the skin, eyes and respiratory tract, and they may cause dizziness, nausea, drowsiness, or light-headedness. Furthermore, in very high concentrations, inhalation of solvents can cause unconsciousness, convulsions and death. Obviously, it is in the artist’s best interest to try to eliminate all of these adverse reactions in order to use solvents in oil painting.
Although all solvents are basically harmful, there are certain solvents that do provide more of a service than a health hazard, and for this reason oil painters tend to use only a small variety of these oil soluble chemicals available. The following is a list of solvents commonly used in oil painting, along with their own individual characteristics. Each has its own benefits in regards to compatibility with oil paint, but each has its own drawbacks.
#1. Gum Turpentine
Turpentine, commonly found in hardware stores, is the most abrasive solvent used for artistic use. It has also been the most traditional material for diluting oil paints. Turpentine is available in different forms, so only artist grade distilled gum turpentine is singled out for oil painting. Turpentine is generally not a good solvent to use for cleaning brushes as it tends to be harsh on the bristles. It also tends to leave a gummy residue when used in oil painting because it contains impurities. However, when working with damar resins found in some mediums and varnishes, turpentine is most effective. Another drawback is that turpentine is caustic on the skin, causing irritation, and emits harmful vapors.
#2. Mineral Spirits (Petroleum Distillates)
A less abrasive solvent that is a better option for cleaning brushes and thinning paint is mineral spirits, otherwise known as paint thinner. Although mineral spirits do not dilute damar resins well, they are less likely to cause allergic reactions. They are also less likely to deteriorate with age. Unless made to be odorless (see below), mineral spirits do emit harmful vapors despite being gentler on the skin.
#3. Odorless Mineral Spirits
Invented because mineral spirits is such a versatile solvent in being more delicate to the skin, odorless mineral spirits allows for the effective qualities of plain mineral spirits, but eliminates some of the vapor hazards. As such, odorless spirits are a great choice for cleaning brushes as well as diluting oil color in painting.
#4. Paint Thinner
Paint thinners are simply synthetic variations of natural based solvents such as turpentine or mineral spirits. They are more useful for cleanup and not recommended for working with oil paints as a medium.
#5. Citrus Thinner
A by-product of citrus peel liquer, citrus thinner is used as a substitute for mineral spirits as it effectively cleans brushes and dilutes oil paint well. However, it is not effective in breaking down damar resins. It has a yellowish color and a slight citrus odor. It is free of petroleum distillates, mineral spirits and other synthetics, and is classified as an extra mild thinner. The benefit over mineral spirits is that it tends to speed up the drying time of the oil paint when blended with it. Citrus Thinner is also more environmentally friendly than pure turpentine.
A very popular synthetic solvent classified as a petroleum hydrocarbon, Turpenoid was created as an alternative to mineral spirits and is odor free. It can be substituted for
turpentine or mineral spirits in all painting functions, but also is not effective in diluting damar. It is also a practical clean up solvent.
In conclusion, it has been my experience that Turpenoid is the most effective all around solvent for my own personal needs. It cleans my brushes well, I like the way it integrates with my oil colour, and I feel safe around it. Moreover, damar resins (the only material insoluble in Turpenoid) are often avoided in oil painting today because of the yellowing tendency and brittle qualities. So, I find that I usually do not need to have turpentine on hand.