I have used the M3 lead test kits to test the blue pain in our living room and I am confused about the result and its interpretation.

The first image was a test I did 2 days ago. in the first 30 seconds didn't turn red from what I could see but after that started to turn this off purple colour which is very difficult to interpret.

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second image same wall about a meter across. (image taken 10-15 mins post test, brown/purple colour didn't start till after the initial 30 second test swab around the 1 minuet mark but deeper colour developed 5-10 mins post)

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3rd image another wall in the room. (similar situation/progression to 2nd image)

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4th image on a wall with paint known to not have lead in it (picture taken 10-15 mins post test).

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final image, another wall in the living room, seemingly same paint as first images but on a different wall in the room (image taken 15-20 mins post test)

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so, as you can see some varying results. my main difficulty is i cant tell if the purple/pink/brown is positive or not. and its dried a different more reassuring yellow colour on the known lead free paint and one of the other walls. the paint is flecking from half the wall down and fine above this. the final image (which is still suspect paint that we are testing) is intact over that entire wall.

I have read (from no where official) that it can change colour to browns/ purple if some other elements/additive/minerals are present. I have also heard it theorised that is is just the way the test dries and 'oxidises' but the test on the lead free didn't yield the same result if that was the case you would imagine it would.

any advice/guidance/suggestions?

Thanks again, really want to get on with the room as we have little space and this was only meant to be a quick redecorating project while isolated (had all materials at home already didn't travel out for it, essential travel and all).

any suggestions / help guidance?

  • 1
    The test kits I have used have a time limit for the test if they do not identify lead in that time line the surface is below the threshold. Over time the chemicals will oxidize and change this is why there is a time limit.
    – Ed Beal
    Mar 31, 2020 at 21:31

1 Answer 1


Welcome and nice first post

You look good. Occurring to 3M a positive will have a distinct red color right away. The test also is not colorless, I personally think for the user to tell where it has been applied and that something is indeed being put on the paint surface

Here is a video about it from 3M

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