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.