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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.

Jasper
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Matt
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  • Hmm, interesting question, short of chemical testing or leftover stamps markings I am not sure there are any other ways to be sure. – James Jul 10 '15 at 15:36
  • I am curious about chemical testing but I don't know what I would be testing for. Arsenic would be obvious but I don't know enough about chemistry and if the surface would contain enough trace for a positive result. – Matt Jul 10 '15 at 15:53
  • Theoretically, combustion spectrometry might do it...There are labs that specialize in testing for lead and asbestos and such; you might want to call one of them and ask what they'd charge. – keshlam Jul 10 '15 at 16:35
  • Most unprotected woods turn grey as they weather, due to UV bleaching among other things. – keshlam Jul 10 '15 at 16:36
  • All the arsenic test kits I'm seeing are for testing water... – bowlturner Jul 10 '15 at 16:54
  • @bowlturner That is what google told me as well. – Matt Jul 10 '15 at 16:58
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    For what it's worth: when i rebuild the frame of my basement "bulkhead" door, I used PT since it was going to have to withstand moisture and possibly bugs --- but used a marker to label every piece as PT lumber, with the year of installation. For this application I didn't care about it being pretty, and this way there is no possibility of later confusion. – keshlam Jul 15 '15 at 22:51

2 Answers2

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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.

Ast Pace
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  • So what you are saying that there is no way to be sure if the green is not present short of chemical analysis. – Matt Jul 14 '15 at 15:07
  • There are field kits that can be used for the chemical analysis. For instance, this one requires a simple 1/4" diameter 1/2" deep drill sample. – austinian Jul 24 '15 at 20:21
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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.

bowlturner
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  • Matt asked in his question how to identify pressure-treated wood if it isn't possible to see the coloring by cutting into the wood. Are you suggesting that it should always be possible to find the coloring produced by the pressure-treating process, either by planing away enough of the surface or by cutting a cross-section? – rob Jul 10 '15 at 16:55
  • I was worried the only way to be sure was to remove some wood but it seems the most likely response. Not all wood is treating with the same process ( I don't mean this a quality issue but manufactured that it was done on purpose as a degree of saturation.) so I would guess that is is possible that the green might not be visually present? – Matt Jul 10 '15 at 16:55
  • It is a valid point that pressure treating using arsenic ( as the case of CCA) is banned that wood still exists out there. In most cases it is obvious like if I was to take deck wood. But smaller projects might not be so. – Matt Jul 10 '15 at 17:00
  • @rob I reread his question and saw that. Oops. However, any wood I've seen that might not be identifiable that way either has questionable useful wood content. It's concentration also is reduced over time. and the center of boards are not treated, – bowlturner Jul 10 '15 at 17:00