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The three types of green solvents that Bob Flexner discusses in his article – paint thinner, lacquer thinner and denatured alcohol.
After a 20-minute drive through Boston-area traffic and a 20-minute walk around the periphery of the home center in search of someone who could direct me to the finishing supplies aisle, I recently found myself staring at a surprisingly limited selection. I had walked right past it a couple times in my little hike. There were maybe six rows of shelves, mostly devoted to stains that I didn’t need.
But there were two options for paint thinner (mineral spirits), which is one more than I expected to find. In addition to the brightly painted metal canister that you see everywhere, there was a white and green plastic bottle with a round sticker that said “non-flammable.” There was also a statement on the label claiming that the product was safer for your lungs and easier on the environment. I was skeptical, but the price was right and I decided to give it a shot.
The “green” mineral spirits have been working really well for me, especially in an apartment living/working space where ventilation and fire safety are of highest importance. When I took the plunge, I had not yet read Bob Flexner’s article on these products. Bob seems to agree that some of the green solvents are very comparable to their other-than-green counterparts.
What follows are the key facts from Bob’s 2012 article on this topic. If you need some of the best advice on finishing, don’t delay in buying a copy of “Flexner on Finishing” from our store during the big Fall Sale. This book is my current pick for your collection!
–Dan Farnbach
Excerpt from “Green” Solvents
by Bob Flexner
On the left, green mineral spirits poured from the bottle and allowed to settle. On the right, two mixtures of oil-varnish finishes that include settled green mineral spirits.
1. Paint thinner (mineral spirits). The green paint thinners are the most unique of the green solvents category. They are emulsions, which means that the oily petroleum distillate is combined with water so that only 30 to 40 percent of the product is actually petroleum distillate. And it is even “greener” than regular paint thinner because some of the bad stuff, such as sulfur and aromatic hydrocarbons, has been removed.
As with all emulsions, green paint thinners are white in liquid form, but the whiteness disappears from the thinner as it dries. Unlike many other emulsions, however, green paint thinners separate if left standing, so you have to shake or stir them before each use.
Another difference to be aware of is the water content. It will cause the first coat of any product you thin with green spirits to raise the grain of the wood. You have to sand off the raised grain, and this risks sanding through to the wood and maybe removing some color if it’s been stained.
On the positive side, cleaning brushes is actually easier with the green paint thinners because of the emulsion.
2. Green lacquer thinners. These lacquer thinners contain mostly acetone and a little very slow-evaporating solvent to allow the lacquer to level and resist dry spray and blushing.
It may take a few trials to get used to the evaporation rate of a green lacquer thinner so you avoid orange peel, but this isn’t different than just switching brands, because all brands of lacquer thinner evaporate a little differently.
3. Green denatured alcohol. To make a denatured alcohol that is free of hazardous air pollutants (HAPs), manufacturers use only ethanol (the alcohol in beer and wine) with a little of something else to make the product poisonous so it isn’t taxed like liquor. Therefore, green denatured alcohols vary little from regular denatured alcohols. They may take a little longer to dissolve shellac flakes, but they are no different for thinning already dissolved shellac.
