Bubbles When Taping Over Paint

raven2006

This is a huge problem for me. I go into a house being renovated and for whatever reason have to tape over a previously painted wall. The mud gets little bubbles. So I put another coat over, more bubbles and so on. Try to sand and there are little holes everywhere. Right now I am fixing a previous bad taping job and the room has been painted. The first coat of mud no bubbles, wow was I happy! Second coat of mud (same batch of mud) bubbles everywhere. I have tried 20 min easy sand, sanding the wall a bit first, thick and thin coats of mud, let it dry a little and then try to smooth them out, but no luck, they just come right back. I've also had one area of a wall with no bubbles, and another area of the same wall get bubbles, it's driving me crazy. I would love some tips on this!

taper71

I have run into this problem lots . What I do is tape ,coat, coat, sand as normal. After it is primed I would come back and find every flaw,and fill those bubbles It has always worked out for me. I also always let the home owner know that this happens when taping over painted walls and unless they want to demo and redo that this will happen.

1KingOfDrywall

Anytime you are going over a painted surface use 20 minute easy sand. A joint compound or plus 3 will not adhere to a painted surface and down the road you can bet the seam will crack.....it's like the idea of bedding mesh tape with Plus 3.....it just doesn't work. It'll hold up when you sand and stuff, but trust me......I seen many a paint roller start flaking apart those surfaces. I always do my tape coat and than first coat over a painted surface with easy sand, than finish as normal. Just like texturing an old smooth painted ceiling. If you roll joint compound, stomp it that knock it down over a semi gloss paint---it'll be chipping off first season. Now.....if you roll out what I call a "tac coat" which is just a thin rolled on application of wet 20 minute easy sand......the joint compound will certanly stick to that. Want an example. Here's how I tested it. I did an area in my garage. I paper taped a surface that had semi gloss paint on it with regular joint compound--4 days later I pulled the tape off with not a single piece of torn paper tape. I did the other with 20 minute easy sand......the paper tape tore non stop It was impossible to get a piece longer than 1/2'' off--it was stuck-Good luck

Norrrrrrrrrrrrm

I have never done this before, but I have read that putting a little dish soap in your mud will cure your bubble blues.

1KingOfDrywall

That soap trick does work. It makes the mud a little fluffier and it runs off your knife quicker......I think it works like a lubricant. It reduces those nasty little pock wholes in the mud, but the bubbles raven was referring too are caused by moisture. But give that soap trick a try on your next job....I am a fan of it.

Frankawitz

Well I used easy sand for the first time since they put this SH#T on the market. we were finishing up a kitchen yesterday and we had used easysand 20 to do some filling of low spots and so we let it dry then sand it out nice and smooth, so then we go and prime, well as we roll out the room everywhere we had used easysand the primer starts falling off the ceiling and walls in sheets, it's like what the F%$K!!! so we scrape it off, turn the heat up wait, then we do it again, going along everything is fine and I bump the ceiling with the roller and sure as sh*t puts a piece off the ceiling, Muther F*&^ER. I tell my brother yeah now I remember why this EASYSAND is SH*T and I wouldn't use it again if they paid me, I'll stick to good old Durabond in the brown bags, we ended up wasting about 6 hours cause of the EASYSAND SH*T, I think we have half a bag left and I'm dumping it in the trash where it belongs. I didn't like this stuff when it first came out back in the 1980's cause it was to soft of a finish, you can take your finger nail and scrape a hole in it, with the brown bag you have to use a knife.
As for the problem you are having with the bubbles take and sand the painted wall or ceiling down you have to knock down the finish of the paint so that your mud can bond to the surface, I would only use DURABOND 20,45,90 in the brown bags, the EASYSAND throw it in the trash.

boman47k

I agree. Sounds like first coat was not completely dry.

sidejobs

What I have heard why air bubble show up on painted walls is because there is no were for the wet mud to dry other than out. The mud on the surface dries first and then the mud behind that starts to dry and in doing so air pockets are created to let that moister out. On an unpainted wall the moister from the mud is absorbed from both sides the sheetrock side and the air side. When you are going over a painted surface the wall can’t absorb any moisture through the sealed side (painted side) causing air bubbles. As in how to stop it, good question??? Hope this made sense.

boman47k

I think it has something to do with moisture and working the mud too much or not enough before or after application. Not sure about your reasoning here though about the moisture not being able to penetrate the wall. Wouldn't that mean oil primer/sealer and mud would not go together very well? I have had air pocks myself. I have also patched over flat paint with no problems that I am aware of. Have not had problems with the pock holes in a while. I do usually thin my mud a little and if I have it, I will put dish detergine in it for smoother flow and workability. Come to think of it, I don't think I have had this problem since I started thinning my mud these past few years. Having said that, I will now prop be plaqued with this problem.

boman47k

Actually, I think it has to do with working the mud to a consistant creamy like texture before application.
P.S. And sufficient dry time between coats!

1KingOfDrywall

when you apply compound over a New drywall surface it's absorption is normal. It can breathe during the drying process and the surface it is attached to is porous. Now, when you go over a painted surface......it is not porous at all......and nothing gets absorbed inwards-by the surface and the drying process is changed. So the air ((which causes the bubbles)) can only move away from the wall to facilitate the drying process. It's just a simple issue of the water evaporating that causes those bubbles. ........easy sand works better in that situation as it dries too fast to get the bubbles unless you made a wet mix or are using 210.

raven2006

Moisture isn't a problem in my case I don't think as these bubbles show up the second I put mud on. I smooth the mud out and they reappear in the same spot. Second coat of mud they reappear instantly in the same spot. As the mud dries there is no change in the original bubbles. It seems to me to be a chemical reaction of some sort between the mud and paint. The only thing that seems to work is repeated layers of mud until they finally somewhat disapear but then again I've put five coats on before and it still bubbled. I've tried the easy sand and it seems to work sometimes.

sidejobs

Thanks, 1KingOfDrywall.

boman47k

i think that is pretty much a given.

drys faster, seems the air would make the bubbles faster. Still has to evaporate. I guess I will continue to add a little water/detergent and mixing to a smooth consistancy until I have problems with the holes again. Been years, but it could happen anytime, I guess. Seriously, I feel stirring and adding water and or detergent helps get rid of some air in the mud straight out of the bucket.

taper71

[quote=boman47k;222076]i think that is pretty much a given.



drys faster, seems the air would make the bubbles faster. Still has to evaporate. I guess I will continue to add a little water/detergent and mixing to a smooth consistancy until I have problems with the holes again. Been years, but it could happen anytime, I guess. Seriously, I feel stirring and adding water and or detergent helps get rid of some air in the mud straight out of the bucket.[/quote

I agree I even went out and bought one of those 6 1/2 " jiffler mixers a couple of years ago. It really keeps air out while mixing.

boman47k

What little drywall work I have done I usually mix and stir with small mud knife in my box. I did burn one small drill up trying to stir some old mud a fella had once. I usuallyuse a 1 1/2" mud paddle or something similiar to pull it back and forth and stir the premix until creamy like and not foamy, almost porous, like it seems to be from the pail. I really like to prework it until I get a slight shine to it. I then try to work it enough on the board to work out as much ramaining air if any out. I look at it kind of like working air out from a car tag. I do not claim to be a pro by a long shot, but I can finish. Need a lot more practice to be efficient as far as speed is concerned.

Drywall1

It's air just as said above. Wall and Ceilings (an industry magazine) did a article on it. Durabond is the only way to keep from it. Or sand the hell out of the paint till you see some drywall paper. Old patches are the worst, when there is a butt load of paint on the walls.

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boman47k

Hmm, someone care to explain this??

Could someone explain why I haven't had this problem in years? I have never used Durabond.

If the pinholes did not sand out, when you remud, you are still trying to cover many smal cavities with air in them. You might fill them if you work the mud over them enough.
I would try cleaning that spot off even if I had to remove the paper and start over. . Mix and stir my mud to a creamy consistancy. Lay my bedding, run my paper through water, lay paper in bedding, cover with mud like you normally would, and let dry overnight. Keep mud worked in the pan occassionally. Next day, final coat (light weight/blue top). All I have worked with is premixed and it slow, but it does work. I intend to try the other setting types though to speed things up and make things like this a one day affair.

Couple of notes: (1) Running paper under water keeps the paper from drawing moisture from the mud, and seems to allow me to use a thinner coat of mud.

(2) Even with adding water to the paper/tape, I still haven't had the pinholes in a very long time

(3) I very, very seldom put leftover mud back in the bucket. I might if mud on top is still smooth and wet looking. Actually, I would advise not doing this. Hmm, just contradicted myself .

Be interesting to see what others say about the way I do this.

boman47k

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That should be decal for the car tag/plates.

1KingOfDrywall

Bro...bottom line is that if you use pan by pan of 5 minute to tape, than do a bed coat with 20 THIS WILL NOT HAPPEN. YES it still has to evaporate to dry....but the longer it takes to set up adds to the number of small air pocks and bubbles. Durabond easy sand dries-or should I say sets up too fast to get the same amount of bubbles. This is really a no brainer....lol. Not really a debate here on this one. It will happen in 100% of situations when going over a gloss or semi gloss paint- it Will not usually happen on a primed surface. The ONLY solution would be is too remove the paint (as Drywall1 mentioned) or use a compound that dries fast. Other than that.....are you from a geographical area low in humidity? Dry air eliminates the bubbles also.?