Patching and Plastering - Drywall bubble

First attempt to finish drywall and I have a quick question about bubbles underneath the paper tape. Ho soon do they form ? Is it a matter of hours after applying the tape ? Or maybe days ?

Thanks much

Frank

Bubbles or loose tape occur for 2 reasons - either not enough mud under the tape [failure to glue it to the wall] or too much mud applied over the tape [before it has dried, pulling it loose]

If you are going to have tape turn loose in spots it will happen before the mud dries. The way to fix this is to cut out the loose and redo. This may be as drastic as retaping or may be as simple as just cutting out the bubble and forcing mud under the tape.

Adding more mud over top of a bubble seldom ever makes it disappear so it needs to be fixed before proceeding.