# Bubbles when taping over paint



## boman47k (Oct 13, 2006)

> are you from a geographical area low in humidity? Dry air eliminates the bubbles also.?:thumbsup:


Alabama, but we do have ac, gas and electric heat. So, not sure about the humidity for interiors. This subject makes me want to experiment. I may take some of the rock i have in the shop hit an area with one or two swipes, work another area like I normally do. Let them both dry and compare. I may have to wear goggles in case I have any exploding mud.:jester: Heheh, bottom line is we all try to find a way that works for us. :thumbsup:


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## Mater (Feb 21, 2007)

C'mon with the 10 grit:laughing: :laughing: !


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## boman47k (Oct 13, 2006)

boman47k said:


> 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.


  I'll just sit here and make very little noise now  . Dang bubbles and holes!


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## Tmrrptr (Mar 22, 2007)

Bo,
We only use 5min.
no bubbles, but we mix it well in the pan and use it pretty wet.
20min &40min fast set give us probs w flaking off.
r


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## boman47k (Oct 13, 2006)

Trying 45 "Easy Sand" here for the first time. Got to get over the learning curve with it, I guess. I tried going a little dryer sfter having it take two days to dry. I then learned not to wait for it to dry to recoat. Going way dryer made it start to set up in the pan. Heheh, first I thought I had picked up some trash. I the realized it was setting up on me! Hurried outside to clean the tools. Had to use 5 in 1 to scrape. It also seems much harder to sand than the regular premix.


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## Ted W (Jan 7, 2007)

Nobody here seems to get it so let me clue you guys in. 

A - The first coat dries. It has air in it, cuz it's dry. 

B - You put a second coat on. The moisture from the second coat soaks into the first coat, which is dry and full of air. The moisture displaces the air, so the air has to go somewhere. On a sealed surface the air has only one way out. Ergo, the bubbles appear. 

C - Third coat, ditto all the above.

So why then does setting type mud not do this? It DOES, when it's dry. But if it's set but still wet, it doesn't have air in it. 5, 20, 45, 90, 300... Easy Sand, Brown Bag... doesn't matter. If it is going on top of a coat that's dry, which is on a sealed surface, it's gonna bubble.

Soaping your mud does not help bubbling. Thicker mud helps some, as it has less moisture to be absorbed by the priviously dried coat, but it's still bubbles. Also, the thicker areas bubble more. Ya know why? More moisture to be absorbed by the dried coat, thus more air forced out. 

The solution? Try to get that first coat as full as you can. The less you have to fill with the following coats, the less bubbling you will have. And finally, one previous poster mentioned going around and fixing the bubbles after priming. Correctamundo! With a little understanding of why they occure, and a little practice, you can minimize the bubbling. Then, after priming, fis the ones that slipped by.

True, if you can mix and apply hot mud fast enough you will have NO bubbling at all. But for most of us it's easier to minimize the bubbling and fix the rest.


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## boman47k (Oct 13, 2006)

I don't know about all that, Ted. I have done some mudding in the past. Makes me wonder why I had bubbles on this last house and not several others as I usually wait for the coats to dry completely. I tend to think I used to much detergent and water to thin my mud this time. Detergent + water = bubbles. Bubbles pop and leave the tiny holes maybe?


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## Ted W (Jan 7, 2007)

boman47k said:


> I don't know about all that, Ted. I have done some mudding in the past. Makes me wonder why I had bubbles on this last house and not several others as I usually wait for the coats to dry completely. I tend to think I used to much detergent and water to thin my mud this time. Detergent + water = bubbles. Bubbles pop and leave the tiny holes maybe?


I'm speaking from 25+ years of working on old apartments and houses. Walls that have seen nothing but flat paint in their existence don't tend to bubble nearly as much, sometimes not at all. But semigloss surfaces are pretty much guaranteed to bubble. This tells me that the porousity of the surface has everything to do with it. I usually soap my mud, about 1/4 cup dish soap per 5 gal. pail, and the results are still consistent with when I don't have any soap on hand.


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## boman47k (Oct 13, 2006)

Ted? When you use soap, do you also add water? I don't mix a whole bucket, just what I intend to use at the time. I might do a little experimenting with some rock I have to see if I can get a grip on this thing out of curiosity. I usually do not have this problem for the most part. Mightmix some up and let it set for a short while before using it. One particular mix I almost knew I had to wet/thin. I had soap *and* water in it. Sure enough I got holes with it. Made me think it was soap bubbles from too much water and soap. Maybe it is just displacement of the water I had in it. Interesting situation.


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## Ted W (Jan 7, 2007)

boman47k said:


> Ted? When you use soap, do you also add water? I don't mix a whole bucket, just what I intend to use at the time. I might do a little experimenting with some rock I have to see if I can get a grip on this thing out of curiosity. I usually do not have this problem for the most part. Mightmix some up and let it set for a short while before using it. One particular mix I almost knew I had to wet/thin. I had soap *and* water in it. Sure enough I got holes with it. Made me think it was soap bubbles from too much water and soap. Maybe it is just displacement of the water I had in it. Interesting situation.


I should have clarified, I only use soap in the finish coat. 

I always thin with water, how much depends on which coat I doing. For the first and second coats I add about 1 quart per 5 gal. of compound. I add more for the finish coat, make it soupy thin.


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## mseneker (Dec 22, 2007)

We have the same issue. One finisher says add a heavier fill coat and do not depend on the finish coat as much. We all have noticed the pen holes when finishing metal corner bead (don't use metal corners anymore). I found it worse when using quick set. However, we used 210 easy sand for the metal fill coat and never thought 20 minute would work best. Have to try that on painted surfaces!

I've always been of the opinion that quick set is also a cause of pen holes in that the later fill/finish coat can not dry back through it.

One sure fire way to avoid the call-back for pen holes is to sand with a vacuum machine or blow on the small patch areas to find the holes that would have otherwise gone unnoticed due to the pen hole being full of sanding dust. Then pull them tight with mud.

I have no answers of my own for this problem other than to include it on the check list for the final job site check. If it's been painted before you mud then check it after sanding. Pull a tight skim coat with a stiff knife and sand in 10 minutes.

PS - durabond is very hard to sand so I'll go with the 20 minute easy sand example used earlier for a possible fix. We are also going to try another suggestion which is to put paint primer on the wall before taping, however, I hate the idea of adding another step in the process.


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