Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I've heard anecdotally that mold will glow green under a black light (UV light). Is this true?

There's a room in my house with a musty odor, and I'm trying to determine the source of the smell. There's a substantial amount of unpainted wood - here is a sample of what it looks like under an ultraviolet light:

Possible mold in wood

(Photo specs: 1s f/4.5 exposure under 2 48" 36W T8 UV lamps.)

Does this indicate mold growth in the wood? (Freshly cut wood exposed to the same UV light does not reflect the same green-yellow color.) I have tried cleaning the surface of the wood with mold/mildew cleaner, to no effect. My understanding of mold growth is limited and I'm having a hard time coming up with reliable information about it.

share|improve this question

What's the humidity level in the room? I'd go get a $12 humidity sensor and see what you got. My understanding that mold can grow >= 60% RH, though there are other factors (e.g. moisture will condense on a cold wall with a lower relative humidity). You may need a dehumidifier if you're too high. Of course that won't kill the mold but will keep it from growing.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.