Epoxy Floor Bubbles and Blisters: Causes and Prevention
Updated
Small bubbles while curing
These usually come from outgassing, which is air escaping from porous concrete, often when the slab is warming up during application. A primer coat and applying while the slab temperature is stable or falling both help.
Blisters after curing
Raised blisters, especially ones that contain liquid, often point to moisture or vapour pressure from below. Testing before coating, and using a moisture-tolerant primer where needed, prevents most of them.
Fixing it
Isolated bubbles can be sanded and recoated. Widespread blistering usually means removing the coating, dealing with the moisture, and recoating.