[Richard Bingham]

Although this thread hasn't been re-visited in five years, confusion and mis-information on the subject of solvents persists. Perhaps some of this information is new since '03?

1. "Turpentine" by definition, is the gum exude extracted from living trees. This includes gum turpentine extracted from Georgia pines, {used in naval stores since pre-colonial times) as well as gum extracted from the European larch, known as "Venice Turpentine" (used in oil painting since Renaissance times) and also Canada Balsam, widely used in the lab to prepare microscope slides, and also of use in certain oil-painting mediums.

2. "Spirits of Turpentine" refers to the clear, water-thin distillate that is collected when turpentine is heated, and is what's commonly known as "turpentine". The solids left behind are rosin (upon which violinists depend), tar, and colophony. A certain amount of these resins and solids is retained in the spirit distillate, and the finest grades of "pure spirits of gum turpentine" are processed three times: hence, "triple distilled".

With the phasing out of linseed oil and natural resins in the paint and coatings industry for commercial and utility purposes, production of top quality pure spirits of gum turpentine has been in decline for sometime, and has been largely replaced by "turpentine" products which are the camp-followers of deforestation in third-world countries. What is commonly available in hardware and paint stores nowadays is a vile liquid, reeking of creosote, which is steam-distilled from slash, stumps, limbs, and other forest wastes. It bears no resemblance to "good" turpentine (what we should be using at the easel) which smells like pine forests after rain.

Pure spirits of gum turpentine is a necessary component to "cut" natural resins for varnishes. Mineral spirits will not effectively dissolve some, while others, such as damar, yield a cloudy, turbid mixture if dissolved in mineral spirits.

The chemistry of pure spirits of gum turpentine is conducive to the drying of oil paint films by introducing oxygen, allowing paint to dry "through" rather than on the surface.

A petroleum distillate, mineral spirits, odorless mineral spirits, and the array of "branded" trade name solvents such as "Grumtine", "Gamsol", "Turpenoid", etc., etc. are all mineral spirits, derived from kerosene, and further refined. As a solvent for cleaning brushes and tools, K-1 kerosene is no more odorous than "regular" mineral spirits, but is more penetrating, and hence a better cleaner. It has a lower vapor pressure than mineral spirits, which means lower emission of hydrocarbons.

"Natural Orange" type solvents contain the oily terpenes extracted from citrus peel waste. Compared to either mineral spirits or pure spirits of gum turpentine, they are extremely active, harsh, volatile, and deleterious to the polymerization of paint films. They can easily remove dry oil paint, and while the citrus odor may be appealing, in a confined space, the volatile hydrocarbons they emit are no safer than those released by either turpentine or mineral spirits. The "cutting", solvent action of these solvents is so extreme, they should not be mixed into oil paints, or any mediums used with them.