What caused my paint to alligator and how to fix it?

Question

I did a drywall patch over my shower, using quick dry joint compound, a few coats with sanding in between. Walls were washed with dish soap and dried prior. A few days later I primed with zissner BIN shellac. Few days after that, I could see a crack around the drywall patch, so I did more joint compound, sanded, primed again with the BIN, then painted with a latex paint. Now the paint is alligatoring everywhere on walls and ceiling all the way down to the original paint, which is latex. I only used one coat of paint and waited 2 days to shower, but it is pretty humid in there typically. I did the exact same thing on the other side of the room with no issues, so I’m wondering if the humidity is to blame? How did this happen? How do I fix it and prevent it from happening again?

Answer 1

Pattern cracking (alligatoring) can be caused by:

1) applying a hard coat (oil base) over a softer coat of paint.

2) applying too much paint per coat.

3) applying one coat over another coat before the first coat can dry...often because the first coat is too thick.

4) inability of top coat by to bond smoothly to glossy finish.

Repair is by:

A) scrape and sand down to original finish.

B) apply primer.

C) apply finish coat of SAME manufacturer as primer.

Answer 2

That could be an indication of moisture behind the wall trying to escape. When you put on the BIN shellac, you basically sealed the moisture in, so it's blistering the shellac.

Similar things can happen if you paint over latex paint with oil, IIRC.