Follow-Ups to Answer from Expert Labman

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petrovich wrote at 2007-05-24 16:10:46
1.) There is a huge difference between Linseed Oil and Boiled Linseed Oil. Technically linseed oil is the same as Flax Oil which you pay for in your healthfood store. The problem is it can be extracted with solvents, just like cheap white vinegar or other such things can be extracted with solvents instead of pressing. I imagine these solvents might release VOCs but, the linseed oil itself, is no worse than olive oil as far as health. Boiled Linseed Oil is a modified linseed oil that drives much, much faster. If you're using linseed oil for wood finishing (or someone else has) changes are it is boiled linseed oil. It used to be, a long time ago, that this meant normal linseed oil which had been processed through heating to make it polymerize quickly. But these days, it consists of chemically modified linseed oil with petroleum based solvent and metallic dryers. The later two of these might pose health problems. Dangerous vapors come from solvent, which is going to be in any oil or alkyd paint, boiled inseed oil, shellac, etc, etc, etc, The difference is, some things have worse solvents than others. o some of your own research before trusting a person who says "shellac is made of tree sap."



2.) SHELLAC IS NOT MADE FROM TREE SAP. It is made from the excretions of the Lac bug. It is not made from Lac bugs themselves (some people will tell you so) and it is completely dependent on processing method as to whether any Lac bugs are killed during the process. Tree rosin has absolutely no relation to shellac. Shellac is a hardened resin from the bug secretions that is left on trees. It is then removed from the tree and dissolved in alcohol for use. There is nothing in pure shellac but this bug secretion and denatured alcohol. You can even make your own by buying "shellac flakes" in pure dry form and adding the solvent yourself. Shellac is highly non-toxic in dry form (once cured) but naturally denatured alcohol has some dangerous fumes. On a scale of solvents, though, it's one of the least toxic ones. In fact, shellac can even be cut with regular drug store isopropal alcohol (91% preferably) but can sometimes go white because of the higher water content in that alcohol.



Do some of your own research. One good book on wood finishing is Bob Flexner's Understanding Wood Finishing, it covers all finishes in terms of toxicity and durability. Also check wikipedia (as a secondary source, and follow all the links to external sites if there are any)

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