You may have noticed that acetone is becoming more widely available. This is primarily because it’s the only commonly available solvent (not counting water) that isn’t classified as a VOC or HAP.
VOC is the acronym for volatile organic compound—that is, an environmental (smog) pollutant. HAP is the acronym for hazardous air pollutant—that is, something that is bad for us to breathe. Though acetone has a strong odor, making it seem to be toxic, it’s actually a fairly benign solvent in vapor form, limited at low exposure to causing only mild irritation to the central nervous system.
Not being a VOC or HAP means there are no regulatory restrictions on how much of this solvent we, or the manufacturers we buy from, use. No other commonly available solvent is so free of restrictions.
Acetone is also very useful because it is miscible (that is, mixable) with all common solvents and water, and thus most common paints, finishes and coloring products. So acetone can be added in significant percentages to most of the coating materials we use. (Water-based products tend to coagulate, however; you should test on a small sample.)
Also important, acetone is the fastest evaporating (“hottest”) and one of the strongest of all commonly available solvents, and it is very “dry” (that is, non-oily). So it makes an excellent cleaner and degreaser and this is how it is used in most other industries.
The fast evaporation corresponds, however, to high flammability. A flame or spark can set off an explosion or flash fire if vapors build up enough. You should always work with good ventilation if you are using the solvent in large quantities.
The strength means that acetone can damage or remove most paints and finishes, so you should avoid using it as a cleaner on all but the most solvent-resistant finishes. These would include conversion varnish, two-part polyurethane, UV-cured finish and epoxy resin.
When acetone is added to stains and finishes, it changes the application characteristics significantly. Any finishing product that contains a large amount of acetone dries very rapidly.
Fast drying can cause dry spray and blushing in finishes and toners. It can also cause an NGR dye stain to dry so fast that it doesn’t wet out the wood enough to bring out the expected color.
You need to be aware of acetone and the effects it is having on the finishing products we use.