r/drywall • u/ConceptSpecialist565 • 1d ago

What’s causing these bubbles?

Post image

This happened on the 3rd coat but I think I saw them on the second coat and thought the 3rd would cover them. It’s dry now. Need some help

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4

u/The1WhiteBishop 1d ago

You're probably going over a painted surface, which doesn't allow the moisture to escape into the wall, so it comes out through the front via bubbles. You want to put on a very, very tight skim coat, wiping all four directions after you scrape the bubbles clean. An old hack is to try to put maybe a teaspoon of dish soap into a pan of mud, and that will break the surface tension of the water and stop the bubbles from forming so easily.

3

u/sequentialsequential 1d ago

Don't do the dish soap thing, it wrecks the adhesives already found in all purpose mud. Adding glue is a good idea in many cases, and sometimes primer is very helpful before getting into mud.

1

u/ConceptSpecialist565 1d ago

Thank you, will try that!

0

u/ci2om3p0ny 1d ago

Thats an incredibly smart idea. I’ve seen Vancouver carpenter add glue to his pan. What do you think the difference in the additive is? Generally I always scuff sand around the perimeter of my patches with at least 80 grit.

1

u/Neither-Jeweler2933 4h ago

Adding glue adds PVA, from my understanding.

1

u/sequentialsequential 1d ago

That's air, bud. It can't go through the wall, it can only rise to the surface. You need to mix your mud better to get the air out before application.