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11/04/2010 |
A lot of the chemicals we use in woodworking, especially in finishing, are toxic. Now there is toxic and TOXIC. There is long term exposure toxicity and one-whiff-drop-dead toxicity. If you want to work safely, you need to know. Not only do woodworkers need to know, everyone needs to know. So We the People, in the guise of "the Federal government," passed a law that requires that for any substance you sell, you must also make available a Materials Safety Data Sheet or MSDS Sheets for short. (Yes, I know the extra word "Sheet" is redundant.) With the introduction of another intrusive government-sponsored initiative known as "The Internet," it's now possible for companies to make MSDS sheets readily available through downloads.
MSDS sheets have information on the chemical makeup of the substance; the long term and short term dangers the materials pose; what safety precautions should be used when handling or storing the substance; and what to do in case of accident. This is phenomenally usefully information for anyone handing any chemical, especially if you are working in your house with suboptimal ventilation or protection or if other members of your family can get exposed.
For example: With all the writing I have done on shellac and alcohol I also took a look at the safety aspect of the various alcohols on the market. If you look at the MSDS sheet for Klean-Strip S-L-X Denatured Alcohol which is inexpensive and commonly available at local hardware stores (FWW used it in their article on shellac in Dec. 2010), you will discover that it contains 45-50% methanol. The MSDS sheet for the product says, "Vapor harmful. May cause dizziness, headache, watering of eyes, irritation of respiratory tract, irritation to the eyes, drowsiness, nausea, other central nervous system effects, spotted vision, dilation of pupils, and convulsions." There's also water in the alcohol, which makes the shellac harder to use - but water is the least of my issues. I just don't want the methanol fumes invading my house and shop. Incidentally the author of the FWW article isn't wearing any protection (gloves, mask, etc.), which I think is an error.
The two most common alcohols used with shellac are Bekhol, a premium shellac sold by Behlen and available from lots of higher end woodworking suppliers and BT&C 200 proof Ethanol alcohol (unavailable and no longer )sold by us and available through us or from Woodcraft. They are both safer and better than the hardware store stuff. If you read the MSDS for Bekhol or for our stuff you find Behol only has traces of methanol in it, and ours has none. Neither has significant amounts of water. Ethanol is what's in liquor, so the exposure limit is pretty high, but one message that comes out loud and clear is that if you use it a lot you should wear lung and hand protection - and of course eye protection just in case. (The stuff is a lot stronger and dangerous to splash in your eye than than your typical mixed drink, although there is no danger from ice bruising.)
The big difference between Bekhol and our stuff is that Bekhol is 30% non-ethanol, of which some is isopropal alcohol, which raises the flash point. That means that the stuff will take a little longer to evaporate, and when you are spraying shellac, this might be an advantage. (You don't want to have the spray to dry before it hits your wood). BT&C alcohol is 99.5% ethyl alcohol (ethanol) denatured with a rubber solvent, so you would get sick if you drank it. With the lower flash point it is perfect for brushing or rubbing on shellac.
Neither product has water in it (the S-L-X stuff does), although if you leave a bottle open it will absorb it from the air. Less water in the alcohol will make dissolving shellac go faster, and produce a harder, clearer finish.
Read the MSDS sheets of the products you use. Don't ignore the safety recommendations just because they come from "The Man." There is a certain air of over-caution in these documents, but they are important. Most of the toxicity of chemicals we use around the shop is cumulative, which means when you find out you have a problem it's too late to fix it.
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Larry
Marquette, MI
All the best,
Brad
So I'm going to assume using this solvent will still mean the Shellac is no longer FDA approved as food safe, but I thought I would ask.
The only question on solvents is how much toxic residue is left after it all evaporates? Methanol is of course very toxic to breath but after it all evaporates is the remaining shellac safe? Same goes for ethanol, which is safer and the various small percentages of denaturants that are used. I have no idea.
Certainly I would rather chomp on a dried shellac finish than a dried lacquer finish but I don't really know if either are harmful in their dried state or not.