Do positive results of a lead paint testing kit imply that a dipped door is now toxic?

Question

(Cross-posted from https://chemistry.stackexchange.com/questions/155681/do-positive-results-of-a-lead-paint-testing-kit-imply-that-a-dipped-door-is-now due to a helpful comment.)

We have had some 1930's doors dipped in a caustic solution to remove the paint.

Before dipping, we found that a layer of yellow paint contained lead. It tested positive with: https://www.amazon.com/Testing-Results-Seconds-Suitable-Surfaces/dp/B07NBH7KJJ/

(The testing kit requires the swabs to be dipped in vinegar, where they change color from white to yellow. Rubbing for 30 seconds against safe paint results in no change from the yellow color, while lead paint causes the swab to turn red.)

What appears to be the bare wood of the dipped doors now tests positive when we use the paint-testing kit. (We were testing a small patch of unremoved paint, and initially tested the bare wood by accident.)

Not only does the bare wood test positive, but it turns a much brighter purple than the red color-change produced by the original lead paint.

Is the door now impregnated with lead as a result of dipping?

Or is this just a reaction between the caustic substance in which the door was dipped and the testing chemical?

Answer 1

The danger from lead-based paint is not the paint surface itself but paint chips that may come loose and get ingested by people in the home especially children who are very vulnerable to its effects.

It sounds as though you have removed all the paint at this point so there is no "detachable" lead on the doors. You're not planning on using these doors for food preparation surfaces but rather going to paint them again, using non-lead paint, and re-hang them. So once you have done that there will be no further exposed lead and nothing to peel or chip off and pose a threat.

If, however, you remain concerned, you should dispose of the doors using a licensed lead-disposal service and replace them. If you plan to keep them and re-finish, you may want to exercise caution if you sand them as that may liberate lead containing dust.

Answer 2

Most likely, the doors were already impregnated with lead before they we dipped. If the first coat of primer that was ever applied was leaded paint, then that will have soaked into the wood.

If you aren't that worried about a bit of lead inside the wood, you can give the doors a few coats of lead-free paint, and the lead will be well sealed in.