# Paint blistering and/or bubbling issues



## slickshift (Aug 25, 2005)

As bubbling is often a moisture issue, this is a little odd
You are correct that it does kind of sound like calcimine at this point
That would be unusual...it really wasn't used in the '70s

I suppose it could also be contamination of some sort, or improperly prepped (not dusted after wash and sand) walls

As it's going down to the first coats now, conceivably, it could also be real old builder's paint as the first coat(s)
-no primer or perhaps no dusting...or maybe then it really chalked up...and the subsequent layers were barely hanging on

A subsequent layer of oil paint could also create havoc later, but that would tend to penetrate and seal in any poor paint originally on the walls
...unless they were really ill-prepared...again possible
(A subsequent layer of calcimine wouldn't)

If it's calcimine, normally a coat of flat oil and a sacrifice to the paint gods should "fix" it

In this case I'd try a test area with a penetrating specialty sealer such as Zinsser's Gardz
It should penetrate any chalky paint and harden it, so it can be patched (and primed) and coated

Gardz would tend not to work on calcimine, but again, that would be pretty unusual

Gardz does have it's limits...I can't tell from here if it's too far gone w/o some tests
But if this is really a case of failing, chalky, paint somewhere in that mix, it's the best bet


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## Nestor_Kelebay (Jun 17, 2008)

Slickshift:

I'm wondering if this could be one of those cases where the original primer or paint was sprayed on without being backrolled so that it was never really forced into the porous surface of the drywall or drywall joint compound to achieve proper adhesion.

Stro77:
How big were the bubbles that formed. If they were very small, like 1/16 of an inch in diameter at the most, then you'll find it helps a lot to wash out the roller sleeve, and then shake or wring as much water as you can out of it before loading it in the roller frame and starting to paint. When you do start painting, your paint will be pretty runny cuz of the water in the roller sleeve thinning the paint. (PS: only use water if you're painting with a latex paint. If you encounter that problem with oil based paint, (which I never have) wash out the roller in paint thinner and wring it out as best you can.) Do the same with your brush to prevent paint from drying out inside the brush and causing the bristles in the brush to flare out.

If the bubbles were much larger than 1/16th of an inch, then I think it's a problem of very weak plaster or joint compound under that painted area. Read on...

You said: "Now, paint is coming off in sheets, and I see this gritty, slightly shiny dust underneath the layers of paint (probably 1/16th to 1/8th of an inch thick)."
I'm wondering if someone has "skim coated" this wall with drywall joint compound after removing wallpaper or scraping off texture from the wall.
What I'm thinking is that if someone thinned that joint compound a lot to make it easier to spread, or misted it with a spray bottle so that it would be easier to spread smooth, then what you may have is paint sticking well to the surface grains of the skim coat, but those surface grains not sticking well to the ones behind them. So, the failure isn't occuring at the skim coat surface, but within the skim coat cuz there's not enough cohesion between the grains of gypsum dust to hold the skim coat together.
I'd take a pail of water and damp sponge and clean that "gritty, slightly shiny dust" to see if it comes off easily with water, and see what's underneath it. See if it looks like drywall badly damaged after removing wallpaper, or some texture that's been skim coated over to make a smooth wall. I think that the problem is that whomever did the work thinned the joint compound so much as to wash all the glue out of it so that the grains of gypsum aren't sticking well enough to each other. The paint is sticking well to the grains of gypsum at the surface, but if they aren't sticking equally well or better to those behind them, then that would explain why the paint is coming off in sheets as the skim coat joint compound breaks just under the surface.


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## slickshift (Aug 25, 2005)

Nestor_Kelebay said:


> Slickshift:
> 
> I'm wondering if this could be one of those cases where the original primer or paint was sprayed on without being backrolled so that it was never really forced into the porous surface of the drywall or drywall joint compound to achieve proper adhesion.


Absolutely
If the original primer was sprayed and never back-brushed/rolled, and/or if they (as is often the case) "let the sprayer" clean off the drywall dust (which it doesn't really), and/or they skipped the prime and went right to flat paint, any/all could lead to a massive failure such as this many years and a few repaints later


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## Matthewt1970 (Sep 16, 2008)

Agreed. This is SOOOO why we prime bare walls and backroll if it is sprayed. I am sure some will chime in and say they have sprayed hundreds of houses with no problems, but the problems don't show up till years later and in your case decades. Paint shrinks when it dries. Every time you put a coat of paint on old paint, it will pull on all the layers below. If the first coat is not properly adheared, it absolutely will bubble.



> Now, paint is coming off in sheets, and I see this gritty, slightly shiny dust underneath the layers of paint (probably 1/16th to 1/8th of an inch thick).


That sounds like one of a few things in your case. Either someone put a skim coat of plaster on the walls that was not properly mixed or like Nestor mention some heavily thinned out joint compound could do that. Or as Slickshift metioned a paint chalking in one of the layers below. 

This is what Slickshift recommended:


> In this case I'd try a test area with a penetrating specialty sealer such as Zinsser's Gardz
> It should penetrate any chalky paint and harden it, so it can be patched (and primed) and coated


I would take that even on step further and get one of those rollers with spikes on it for wallpaper removal and run it all over the walls to help the primer penetrate. Once you do that put the primer on nice and thick so it will stay as wet as possible as long as possible to ensure maximum penetration and soaking of the bottom layers.


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## Nestor_Kelebay (Jun 17, 2008)

Matthew:



> Paint shrinks when it dries. Every time you put a coat of paint on old paint, it will pull on all the layers below. If the first coat is not properly adheared, it absolutely will bubble.


Just to make sure than no one reading this thread dets the wrong information, what you said is only true of latex paints. They develop a tension in the paint film as the resins coalesce and pull on one another. That tension between resins results in there being a tension throughout the entire paint film, and it can be a fairly strong tension.

Oil based or epoxy paints don't develop any tension whatsoever. This is why it's recommended to stick with oil based primers and paints when painting over chaulking paint. Because the surface the paint is applied to may not have any strength, a latex paint can pull right off a chaulking old paint, whereas an oil based primer or paint is more likely to remain in place because it doesn't develop any tension in the paint film as it dries.


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## stro77 (Nov 14, 2008)

Nestor_Kelebay said:


> How big were the bubbles that formed.


The bubbles vary in size from too tiny to scrape off up to about a silver dollar. I'm definitely thinking now (after having stripped most of one wall) that the wall was skimmed with (like you said) joint compound that is thinned out too much or a wall that wasn't properly cleaned to remove dust before painting. I'm thinking I will try to prime the walls I haven't stripped to see if a good oil based primer will keep the bubbles from forming. The places where I spot primed with a spraycan of oil based primer (though it went on much thinner than if I didn't spray it on) did not bubble. I will then re-skim the wall that I did strip. Should I sand and prime the wall I did strip before I skim it? Or should I just prime the skimmed wall after it is skimmed? 

Thanks for all of the replies...this weekend paint job somehow turned into a two-week paint job.


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## Nestor_Kelebay (Jun 17, 2008)

Stro77:

Sanding the soft surface layer of joint compound off would work. 

However, I believe you could solve the problem by diluting some white wood glue with water to make a dilute glue solution and painting that on the wall with a roller. The dilute glue will be absorbed into the joint compound by capillary pressure and glue all the gypsum grains together as it dries.

Or, that's what I'd try first.

If you notice a darkening of the joint compound as you paint the dilute glue on, that means the liquid is being absorbed. If it wuz me, I'd probably apply the dilute glue until I saw no further darkening of the wall as a result of painting the dilute glue on. (Stick around this web site and you'll be able to explain why that happens.)

I'd be scared to use a latex primer over that because the moisture would re-emulsify the glue and you'd just make a big mess.

I'd prolly then put an interior oil based primer over a small area of that, allow to dry, stick some masking tape to the primer and pull it off. If the joint compound holds, then do that everywhere you scrape the paint off to reveal the weak joint compound underneath.

What do others think of this gameplan. Where can it be improved?

One suggestion might be:

You could go to any construction materials supplier and buy a gallon of "concrete bonding agent" instead of white wood glue. The difference is that white wood glue is much thicker and will re-emulsify if it gets wet and stays wet even years after it first dried. However, concrete bonding agent has a time window where the moisture of wet cement will re-emulsify the bonding agent so that the wet cement sticks to the old concrete. After that time window closes, a chemical change takes place in the concrete bonding agent so that it's unaffected by water. So, ideally it would be optimal to use a concrete bonding agent instead of white wood glue, wait for the time window to close, and then prime the walls with an interior latex primer. (then do the tape test before proceeding with paint)

Also, concrete bonding agent comes diluted to a paintable consistancy because it's meant to be painted onto concrete.


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## ohman (Jun 23, 2009)

I have a related question. Our master bedroom interior wall has minor paint blistering and/or bubbling issues. After we talked to a contractor and a professional painter, they both mentioned that it could be moisture or steam got trapped in the wall (plaster) that caused the issue. I then inspected the exterior of that particular wall, and found that the DirectTV guy might have drilled or nailed some holes on the exterior wall, which then allowed moisture to permeate into the wall. Because this particular wall is always facing strong sunlight, so moisture might have became steam and thus the inside wall bubbling...

Here is a picture of the exterior wall:


Here is a picture of the inside wall (water stain and bubbling):


My question is, what's the best way to caulk (and what type of caulk should I use) to make sure that the moisture won't penetrate again?? Thoughts or comments? Thanks!


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