Michael Dresdner

straight talk about wood finishing

Acetone and the VOC question

Q: I found some conflicting information on thinning nitrocellulose lacquer. Some very good finishers use straight acetone while others write of using lacquer thinner. I realize lacquer thinner is a soup so there are many possible formulations, but generally I was wondering how acetone might behave differently from thinner.
A: Acetone, a ketone, is one component of lacquer thinner. Others include esters, glycol ethers, alcohols and possibly aliphatic hydrocarbons. Each component has a particular task, and in some cases, a mixture or variety will be a more effective solvent. A lot depends on the resins in the lacquer itself. The manufacturer of the lacquer will know what the best thinner mix will be, which is why some lacquers come with specific thinners likely to work better than the wide spectrum ones available in home and paint stores.
One trend in the industry is to reduce VOCs, either for green reasons or to placate EPA inspectors. Acetone is an exempt solvent, thus it is not, legally, a VOC. For shops trying to reduce their VOC output, using acetone instead of lacquer thinner is a useful strategy.
Generally speaking, acetone is a faster solvent than most lacquer thinner mixtures. It’s rarely as effective as a wide spectrum solvent. Thus, adding acetone alone will most likely change the way the finish behaves. Whether it is better or worse for your style of spraying and finishing needs is a very subjective question. Try it and see if you like it better. I should warn you, though, that some lacquers, such as those that require high levels of glycol ethers as their primary solvent, will not behave as well with an overabundance of acetone in the mix.