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Posted by Sherman in Idaho [72.47.9.37] on Monday, October 22, 2012 at 21:09:49 :
In Reply to: Re: Outside wood preservation? posted by Paul(in NY) [12.64.102.24] on Monday, October 22, 2012 at 19:13:59 :
30 years ago "Woodlife" was basically pentachlorophenol (sometimes called "penta") in mineral solvent. It killed bugs and fungus very well and lasted a long time, but is carcinogenic and generally bad for you. I got some on my arm when I was a kid and it broke out in a rash. I'm pretty sure the EPA banned it a long time ago, along with good old coal tar creosote. The main wood preservatives they sell these days are copper and zinc napthenate. They're fairly non-toxic but not nearly as effective either, and they leach out after a while. The green stuff you see is the copper. The pressure treaters used to use CCA (chromated copper arsenate) but of course that's been banned too. Some "treated" wood these days has nothing more toxic than borax in it. They still make a product called "Woodlife" but it doesn't have any real poison in it like it used to.
Personally, I'd go with the used motor oil myself -- the more used the better because the more used it is, the more it's like creosote -- full of a variety of toxic stuff, tar, sludge, and acids that will poison the wood for a long time and also help waterproof it. I knew a guy who finished the inside floor of his house with used oil and it actually turned out really nice looking, and after it had soaked in and been walked on a little bit, it wasn't even messy or slippery. Of course you have to put it on when the wood is bone dry so it will really soak in, which probably means next summer at this point.