Took me 3 hours to figure out why my mud was bubbling

Last Tuesday I was finishing a ceiling job in an old house near Cleveland. I mixed my all-purpose mud just like always, but when I started taping, the compound was bubbling up like pancake batter. I thought maybe the mud was too thin, so I added more powder. Kept bubbling. Then I checked the temperature and humidity, both fine. Finally after 3 hours of fighting it I called a guy I used to work with. He asked if I had cleaned my mud pan. I had not. Turns out there was old joint compound residue in the pan that had turned and was releasing gas. Cleaned the pan, mixed fresh mud, problem gone. Has anyone else had this happen with a dirty pan or am I just the only one who forgets to rinse?

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2 Comments

lilyb275mo ago

Hate to be that guy, but the gas theory is a little off. That bubbling is usually from moisture trapped under the tape or from the mud drying too fast, not from old compound releasing gas. Old mud can get chunky and break down the bond, but it's not gonna create air pockets like that. More likely the residue in the pan was letting the water separate from the mix, making the compound not stick right. You probably had thin spots that let air push through as the mud set. Ever try scrubbing the pan with a stiff brush instead of just rinsing it?

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kim_smith5mo ago

Yeah that tracks. I've had old compound get kind of stringy and weird but it never made bubbles. The bubbles always came from me being lazy and not mixing good enough or working it too fast. Scrubbing the pan makes a huge difference too, especially if you let it crust up between jobs.

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