Woodworking Asked on January 10, 2021
New lumber that is pressure treated will have tags that identify the chemical used. More noticeably is the green or brown colors from the treating process. So newer wood is easier to identify as treated. As the treated wood ages it can turn a grey colour. This might not be a good comparison but some cedars turn a similar grey colour over time as well.
Assuming I do not see tags and the (treated) colour has disappeared is there a way to tell if the wood was treated or not?
Sure I suppose I could cut into it but I have seen some wood where the colour was not obvious in a cross section. Another thought would be to do a test for arsenic but I don’t know how good of a test that will be.
I don’t want to take this wood if it can be avoided. For those that don’t know I am a big upcycler and use reclaimed wood frequently. I have misidentified pressure treated in the past as was wondering about tips.
Any wood left untreated and allowed to weather will eventually turn gray. In the days before pressure treated lumber was prominent, people stained or painted their decks and other outdoor projects to protect them from rot and graying. With the advent of pressure treating, the advice and common practice became to "let it weather naturally".
Determine the history of the wood
Assume the wood has been treated with CCA if you think the wood could have been processed prior to 2003 (the year that EPA said to stop this silliness). Or if you have found an out-building from prior to about 1970, you can proceed to up-cycle with confidence.
Look closely at the wood
Surely there are places where part of the wood that was protected from the effects of weather by a lap joint or a piece of trim. If you see any green in the overlap, it's CCA.
Cut into the wood
Don't plan on seeing tell tale green by cutting off an end; it will be too hard to see. Instead, make a very low angle cut as though you are making a scarf joint. You should might see a transition from gray (weathering) to green (CCD) to yellow (wood). The inability to see green is not a sure sign that there is no CCD, but he presence is a positive indicator.
Forget it if you really want "clean" wood
Short of chemical or spectral analysis (expensive and I suspect a violation of up-cycler credo) , you cannot be certain that the wood is not tainted, but you might be able to confirm your suspicions that it is. It looks like there is a chemical analysis kit (thanks to @Austinian) that will give you five tests for under $30 US.
Correct answer by Ast Pace on January 10, 2021
Well they quit using arsenic a while ago now, So that would only be partially effective test. Granted the more important one, since the new stuff is supposed to be much safer.
However, if you have a small hand plane, you can do a few quick passes to see if you get down to the 'green' color popping out. doing this on the 'least' aged side would be the fastest.
The next best requires keeping a hand saw handy, and cutting off the end of the board to see the pressure treated pattern.
Answered by bowlturner on January 10, 2021
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