I had some mold on the ceiling of my bathroom. I scraped it off with a sponge. The thick black mold has gone, but there are still fainter grey stains all over the ceiling which won't come off, even with bleach. I sprayed on PolyCell mould killer (UK product).

How do I know whether or not that has worked? I was told the area would have to be completely dry for it to work. There is obviously a lot of moisture around there every day when we have a shower.

If I now paint over the ceiling with anti-mold paint, how can I be sure the mold is not festering underneath it? Does anti-mold paint prevent existing mold from growing underneath, as well as preventing any new mold from coming on top?

2 Answers 2


To be sure you can buy a mold test kit at your local home improvement store or even on amazon. It's probably not perfect, but might set your mind at ease if you're unsure.


Mold needs 3 things to grow, food (organic materials), moderate temperatures (> 40F <100F) and moisture.

Remove any one and it can't grow or 'fester'.

Vent fans on timers (10-15 after shower) really help reduce moisture. Your anti mold paint will work at the surface.

Occasional surface washings (Monthly (spray and wipe off, really)) will eliminate the spores somewhat. The problem is that they are everywhere.

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