Bleach will not kill mold. It can actually feed it.

In simplistic terms, think of bleach as being "bleach" and "water". The "bleach" part, because of it's chemical make-up, will not penetrate into many materials. It doesn't soak in. It simply sits on the surface. The "water" that carries the bleach? It does sink in and penetrate many materials. And what helps create an environment for mold and mildew to thrive? Moisture!

When people use bleach, sure the discoloration of the mold goes away because the mold that sits on the surface is indeed killed by the bleach, and the discoloration is "bleached" away. But the water penetrates, feeds the roots of the mold, and the mold will usually return.

Try this product to actually kill the mold: Concrobium Mold Control. It's available at the box stores. Kill the mold, then prime with a primer/sealer from the Kilz line. Or with any other good primer/sealer that you can find.

Then paint with any decent bathroom paint.

The Concrobium will kill the mold and mildew.

The Kilz primer/sealer will prevent any stains from the mold/mildew from being activated by the primer or paint and bleeding eventually bleeding through the final coat of paint. You can do more than one coat if you choose. Just read the directions for recoat times.

My recommendations at least. Just an opinion.

Thanks. What about questions 1 and 2? What kind of primer to put on the existing paint?

Your questions all were answered. Mongoct named the products to use. I'd like to suggest a more powerful fan too, with a timer so you can run it long enough to get the moisture out.

-Babka

Babka

Does Kilz only make one type of primer? I thought they had oil and latex versions. That is why I asked. Also I didn't see anything about sanding the ceiling in the original response.

Perhaps someone else can help with those questions.

I went with Zinsser Bulls Eye primer. Two coats. Followed by Zinsser Perma White matched to my ceiling color. Not sure how many coats I will do of that.

Hmmm. Part of my primer reply didn't get posted. So here's the inadvertently deleted part plus a bit more:

1) I'd use either Zinnser BIN primer/sealer, the shellac-based one...

Or KILZ original.

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2) Follow the instructions for using the Concorbium. I wouldn't sand after using it. If you did want to sand due to required surface preparation, ie, the ceiling simply needs to be sanded, then I'd first use Concorbium as an initial treatment. Then clean or wipe down. Then sand. Then another treatment of concorbium. Then a wipe down, then prime. Prime following the primer instruction. Then paint according to the paint instructions.