(I copied the text hereafter from my latest journal entry http://www.brianhavens.com/tab/shop-journal so that my buds at Lumberjocks would not miss this safety issue.)
It is hard to read an article about finishing wood, these days, without some mention of “low VOC’s”. These articles vaguely characterise these low VOC finishes as somehow good for humans. It reminds me of those Life cereal commercials that I grew up with:
“Some low VOC finish; supposed to be good for ya”
“You gonna try it?” “I’m not gonna try it! you try it” “I’m not gonna try it.” “Lets get Mikey” “Yeah!”
Anyone who has read such an article gets the gist: that a low VOC formula contains lower quantities of harmful stuff that evaporates into the air. The key thing to remember here is “into the air”, but I will get back to that in a moment. The burning question that I had is: “What are they putting into these formulas instead?
A little time spent Googling, and I discovered something called “exempt solvents”. There are certain solvents that can be added to solvent based finishes, solvents that evaporate just as well as the solvents in standard lacquer thinner, but that do not count as part of the VOC emissions of the finish. The most popular “exempt” solvent seems to be acetone. Huh? That’s right, a manufacturer can load up solvent based finishes with acetone without adding to its VOC rating.
So why is acetone exempt? After all, it evaporates quite readily. The answer is simple: because acetone vapor does not “go up” into the air. Acetone vapor is twice as heavy as air, which means that it collects along surfaces. This adds an additional danger when using such low VOC finishes. If acetone vapors have no place to escape, they can collect and build up on the floor, posing a risk of explosion. (Consider that most home-made finishing booths are constructed with the exhaust fan off the ground.)
I could go on and on about all the different exempt solvents, and their particular safety caveats, but I am no chemist and that is not the point of writing this article. The point is: Do not assume that low VOC finishes are any safer than their high VOC sisters. (One could even argue that, due to exempt solvents, low VOC formulas simply move the pollution from the air to the soil and water, but that is another article.)
Although I have been primarily talking about solvent based finishes, I cannot exclude water base finishes. Do not automatically assume these are “safe”. They contain, for instance, glycol ether, which I have read varying opinions about its toxicity.
One last note, a disclaimer, before I run. I want to make clear that I am not a chemist, and as such, I am partly speaking outside of my field of expertise here. I culled the information for this article from the research that I have been doing for the purpose of keeping myself safe, and want to share what I have learned with other’s so that they may stay safe as well. If you are a chemist, and want to add something, please, by all means, I invite you to add a comment.
-- Brian Havens, Woodworker http://brianhavens.com