Fixing drywall joints - bubbles came up when I primed

Hi,
I just had some work done in my kitchen which included some wall repair. The contractors fixed the drywall and laid a couple of coats of mud (the contractors are gone and are not returning). I put on what I hoped was a final coat of mud and sanded. I didn't notice any bubbles at this time. I then put on a water-based primer and I saw some bubbles arise. I realize this is bad, so I sanded down as much of the mud as I could (the paper started to shred). The tape appears flat, but I can press in some of the paper in areas of the repaired wall joints. From some posts I have read in this group, I guess the water in the primer soaked into the tape and caused the bubbles. So what do I need to do? I think if I continue sanding I will start to rip the paper. Can I use an oil-based primer to lock down the paper and tape? Then lay some more mud, sand and prime (oil-based this time!)? Will this work? Any advice would be appreciated.
thanks,
Brendan
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In article
snipped-for-privacy@hotmail.com says...

The mud hasn't been ut on thick enough. Back up a step or two and put at least two more layers of mud on (using a six, then 12 inch tool), sanding between coats, then restart your painting process.
--
Mark

The truth as I perceive it to be.
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If you get a bubble, it means that the paper tape is not stuck to the drywall face paper. No amount of sanding can fix it, you will just tear it up. When you see the bubble(s) cut them open with a utility knife. Use wetter rather than dryer taping mud. Force the mud into the cut, you need a full wet coat under the tape. You may need to open some of the joint up to win.
You will get the same bubbles when you apply the top coat of taping mud. This is when to watch for them, find then, and fix them. Really miserable to find them under coat 1 or 2 of paint.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing. . . . DanG

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DanG wrote:

I'd go with Brendan. When the mud and tape was installed there was not enough mud to bond the tape. The tape has tiny hole in it that when pressed against the mud on the joint will ooze out joint compound insuring a good bond then when you apply the second coat it gets knocked down and becomes smooth. The best thing is to open the tape at the bubble with a sharp utility knife and get mud behind the tape. Then once dried apply another coat of joint compound over the fix and feather it in. This should fix your problem.
Rich
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but you can't make them THINK"
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Thanks for the suggestions.
I'm not positive but I think there is a gap (approx 1/4 inch) between the two pieces of drywall where the bubbles are forming. If this is true, then there is no paper for the tape to stick to. Do I just fill this gap with mud? Also I was concerned that once I cut the tape, the tape would lose its strength and I would get cracks. Also, I had a friend just tell me I should cut open the tape, fill the gaps with mud, then retape the area. Is this overkill?
thanks again, and sorry for the newbie questions. Trying to learn the right way instead of doing things twice!
Brendan

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I really do not know how to advise you.
If it were brand new work, you would fill the joint with well blended compound, place the paper tape over the joint, and wipe in with your knife. As you wipe the tape in, the excess mud will ooze out from under the tape; you continue wiping and squeezing the joint until the tape lays flat and the edges of the taping mud are feathered tight to the wall (you do not want to squeeze all the compound out from under the tape, you are trying to bed the tape in compound). Experience helps here, but now is the time to study the edges of the tape to see that they are well stuck to the drywall with a full wet coat of compound under the tape. Now is the time to fix any portions that are not.
It sound like you may have a slightly starved joint between two sheets. The bubble happens because there was not enough mud to coat the underside of the tape. If it is a limited area, I would try some spot repair. If it is generalized, you would probably be ahead to just pull off anything that is loose and start over. A few holes in the tape are no different than similar holes in the face paper of the rock. Slit 'em and fill 'em.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing. . . . DanG

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