Thinners and Solvents
Turpentine

Wood turpentine is extracted, not from the living tree, but from logs and stumps which are ground up. It has a heavy strong odor, and it is generally considered inferior to gum spirits as an artist's material.

Turpentine that is to be combined with varnish or resin should be kept free of water. Varnish containing water moisture may dry with a cloudy effect known as bloom.

Even if it is of the best quality, turpentine may age badly, becoming thick and yellow, especially if it is exposed to light in a clear glass container. The spoilage is accelerated when the container is partially empty, allowing more air to react with the turpentine. For this reason the bottles containing turpentine should be made of dark glass or fitted with an opaque sleeve of black paper to keep out the light. When a container becomes partially empty, the remaining turpentine can be transferred to a smaller bottle so that it is less exposed to air. If turpentine is stored so long that it becomes gummy and discolored, the artist should discard it as it will interfere with the drying of the varnish or paint with which it may be mixed.

Turpentine is generally considered a safe material, provided it is used with caution. Its flash point is about 96° F.

Some painters may find that they become highly sensitive to turpentine. Such individuals may develop blistering skin irritations on their hands after contact with even small amounts of turpentine. The inflammation usually subsides after turpentine is excluded from the painter's working procedures, but the condition may return with even stronger effect over a larger area if the painter comes in contact with turpentine again. Although most artists do not develop such allergic responses, the daily use of turpentine to remove oil paint and varnish from the painter's hands promotes undesirable dryness and makes the hands more susceptible to irritation from such granular dust as charcoal, pastel, and pigments. Prepared hand cleaners and soap compounded especially to remove grease would seem a preferable cleanup material. Mineral spirits, described later, seems to dry the skin less than turpentine does and might be preferred in cases where soap is not adequate.

Although turpentine vapors are not considered especially poisonous, in class situations where ten or more people may be working in one studio, each with an open container half full of turpentine for a brush cleaner, and where the room temperature may reach 75° to 80° F. with very little ventilation, the atmosphere may become unhealthy. Solvents used for brush cleaning should be in brush-washing containers that have hinged lids so they can be closed when not in use. Thereby unnecessary evaporation of solvents into the studio atmosphere can be avoided. Such brush washers can be obtained at art supply stores, and aside from being convenient aids for brush cleaning, they reduce considerably the concentration of undesirable solvent fumes in the studio. [p. 38-39]