# Skim Coat over Primer



## oh'mike (Sep 18, 2009)

You waited long enough---for some reason the primer didn't bond well enough---

Drywall primer may have been the wrong primer---it is designed to seal raw paper and mud--not a painted surface---

A painter will be along with the right primer---I like water based Zinser 123---Mike---


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## Brushjockey (Mar 8, 2011)

Mike touched on it- if you used something that was made for porous sheetrock and mud over sealed paint- it wasn't a bonding primer- so it didn't. 
describe the walls you primed over.


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## chrisn (Dec 23, 2007)

Too much dust on the wall?


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## cougar01 (Jan 22, 2009)

I used SW Drywall Primer. It was over an area where I had done some joint compound work. After primering, I noticed a few imperfections that I wanted to skim coat. When I did, it peeled off of the area with the joint compound. I did wipe the walls down with a damp towel before primering so I don't think that dust was an issue. On another area with the joint compound that needed a touch up, I had no issues.

The walls are part existing drywall that I sanded the paint before starting any work. Previous owners had dust, lint, paint blobs, runs all through the paint that we wanted to sand out. I have joint compound everywhere due to nail pops, dents, skim coats, etc. A few sections have new drywall pieced in because the old was just too damaged to repair.......so the walls are a combo of previously painted surface (sanded), joint compound skim coats, and new wallboard. That's why I chose the SW Drywall Primer.


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## Gymschu (Dec 12, 2010)

Skimming over drywall primer does that sometimes. The mud is wet and wicks its' way into the primer film and reactivates the dried mud underneath. A sealer/bonding primer would work much better although there are no guarantees. Let the bonding primer dry for 24 hours to be safe.


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## Brushjockey (Mar 8, 2011)

I would think a quick coat of Gardz would make a vapor barrier and you'd be good to go in no time.


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## chrisn (Dec 23, 2007)

Brushjockey said:


> I would think a quick coat of Gardz would make a vapor barrier and you'd be good to go in no time.


 
Yes indeed :yes:


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## cougar01 (Jan 22, 2009)

Update----Well, I took my sanding sponge, and lightly sanded the area where the primer peeled off. Applied another light coat of joint compound to this area, and all is fine. The joint compound overlapped the peeled primer area and onto a primered surface. No peeling. It was just this 1 section that it happened to, so maybe the primer just didn't bond well in that spot. The other areas that I skim coated over some imperfections came out fine. Didn't bother the primer. Live and learn I guess. Thanks for all of the suggestions!


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## cougar01 (Jan 22, 2009)

NEXT FIASCO!

Ready to give up. Primered the walls with latex drywall primer and saw some imperfections in my joint compound work. Allowed primer to dry for 24-48 hours, and skim coated the imperfections. After 24 hours, sanded jc and spot primered the areas. Most came out fine, but I had a few spots where the primer blistered over the joint compound. Small blisters like the size of pinheads, although 1 or 2 are slightly larger. It was only light skim coated joint compound, and I let it dry 24 hours before sanding flush and then primering. Prior to primer, I wiped the patch with a very lightly damp rag....hardly wet at all --- to get any dust off. Then dried it with a dry towel. Trust me, the damp rag was barely damp and the patch was dry before painting. 

My guess is that some sort of moisture got sucked into the joint compound? Anyways, I sanded the blisters back down after another 24 hours letting the primer to dry, and reapplied another coat of primer over the area. Blisters reappeared in the same spots. :furious:

So now what? I was planning on leaving everything sit until next weekend (1 week), sand the blisters back down, spray on white pigment shellac over the area, sand it smooth, and either (a) spot prime the area if it looks OK or (b) skim coat if blisters left noticeable imperfections and then re-primer. Or----do I need to do something else?


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## jsheridan (Jan 30, 2011)

Leave the damp rag in the sink where it belongs. After sanding, dust it off with a dust brush. In all my years of painting, if I ever wiped walls with a damp rag, I can't remember it. A towel will not dry damp joint compound, it must air dry. If you sand the blisters out, then apply shellac, why would you need to prime? Shellac is a primer. Sometimes you can get into trouble with very fine skim coats over a sealed surface, which may be happening to you. Sand the blisters out, spackle them, then apply the bin (skip the drywall primer step), then finish. You should be fine.


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## chrisn (Dec 23, 2007)

jsheridan said:


> Leave the damp rag in the sink where it belongs. After sanding, dust it off with a dust brush. In all my years of painting, if I ever wiped walls with a damp rag, I can't remember it. A towel will not dry damp joint compound, it must air dry. If you sand the blisters out, then apply shellac, why would you need to prime? Shellac is a primer. Sometimes you can get into trouble with very fine skim coats over a sealed surface, which may be happening to you. Sand the blisters out, spackle them, then apply the bin (skip the drywall primer step), then finish. You should be fine.


 
Will this not flash? I think so. He will have mostly a surface with his SW drywall primer then his patched areas with Bin, sounds like flashing to me, although,I guess it depends on the finish coats.:whistling2:


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## jsheridan (Jan 30, 2011)

chrisn said:


> Will this not flash? I think so. He will have mostly a surface with his SW drywall primer then his patched areas with Bin, sounds like flashing to me, although,I guess it depends on the finish coats.:whistling2:


There's a possibility of having a shiner if the finish is flat, but I've been finding them more and more rare these days, to the point where I don't really consider it anymore. I guess to avoid taking the chance, the bin could be hit with the drywall primer. Good point.


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## cougar01 (Jan 22, 2009)

THANKS! When I sanded the blisters out the 1st time, I really couldn't see any marks left behind, but I skim coated to be safe. They are so small ---- literally pinhead size. When I first saw them after primer, I thought they were small pieces of dust or whatever that got caught in the roller or paint. They sanded out easily with a sanding sponge which led me to believe they were pieces of lint or dust. Then I realized they were small blisters. Anyways, per your recommendations, I will sand them out with the sanding spong, shellac the area, then primer. Think I will skip the joint compound and/or spackle step unless 1 of them really needs it. I think that the several skim coats over the sealed surface is also an issue, because that's what I've been doing trying to get everything just perfect. I need to learn that plain wallboard is never perfect. Am planning on topcoating with a satin finish. 

Thanks for all of your help. This bedroom has been one thing after another. We've stripped and remodeled other rooms in the house without too many issues. This room, which we really thought was going to be the easiest of them all, must have a curse on it.


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## jsheridan (Jan 30, 2011)

Since you are applying satin, and you already have satin first coat on, don't prime over the shellac. You may cause the opposite of the concern that Chrisn mentioned and I concurred. The primer is flat and may draw some sheen out of the only coat of satin you will have over the patch, and will vary from the rest of the wall which has two coats of satin. The shellac is a sealer and closely mirrors the sheen of the satin.

Practice progress, not perfection, which cannot be attained.


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## chrisn (Dec 23, 2007)

cougar01 said:


> THANKS! When I sanded the blisters out the 1st time, I really couldn't see any marks left behind, but I skim coated to be safe. They are so small ---- literally pinhead size. When I first saw them after primer, I thought they were small pieces of dust or whatever that got caught in the roller or paint. They sanded out easily with a sanding sponge which led me to believe they were pieces of lint or dust. Then I realized they were small blisters. Anyways, per your recommendations, I will sand them out with the sanding spong, shellac the area, then primer. Think I will skip the joint compound and/or spackle step unless 1 of them really needs it. I think that the several skim coats over the sealed surface is also an issue, because that's what I've been doing trying to get everything just perfect. I need to learn that plain wallboard is never perfect. Am planning on topcoating with a satin finish.
> 
> Thanks for all of your help. This bedroom has been one thing after another. We've stripped and remodeled other rooms in the house without too many issues. This room, which we really thought was going to be the easiest of them all, must have a curse on it.


 
Never going to happen. If you are that close to the wall to pick out PINHEAD blemishes, then you are getting way too picky. That's my opinion for what it's worth.


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## cougar01 (Jan 22, 2009)

> If you are that close to the wall to pick out PINHEAD blemishes, then you are getting way too picky.


:jester: Yes, I'm finding that out the hard way. 

As a correction, I only have primer on the walls, I haven't applied the topcoat (satin finish) yet to any part of the walls.


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## jsheridan (Jan 30, 2011)

If you only have primer on the walls now, I would spot prime the shellac with drywall primer to create a fully uniform flat surface on the walls. 
If you're close enough to see pinhead holes, you're too close. I usually hit small missed nail holes with caulk as I'm rolling, spackle for them at the point you're at is overkill. A typical sheetrock wall is riddled with minor imperfections that will drive you nuts if you let it, don't. You can't chase every little thing that most people, other than you, won't even notice.


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## chrisn (Dec 23, 2007)

[quote=jsheridan;899709]If you only have primer on the walls now, I would spot prime the shellac with drywall primer to create a fully uniform flat surface on the walls. 
If you're close enough to see pinhead holes, you're too close. I usually hit small missed nail holes with caulk as I'm rolling, spackle for them at the point you're at is overkill. A typical sheetrock wall is riddled with minor imperfections that will drive you nuts if you let it, don't. You can't chase every little thing that most people, other than you, won't even notice.[/quote]



THAT"S what I was getting at earlier:yes:


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## jsheridan (Jan 30, 2011)

chrisn said:


> [quote=jsheridan;899709]If you only have primer on the walls now, I would spot prime the shellac with drywall primer to create a fully uniform flat surface on the walls.
> If you're close enough to see pinhead holes, you're too close. I usually hit small missed nail holes with caulk as I'm rolling, spackle for them at the point you're at is overkill. A typical sheetrock wall is riddled with minor imperfections that will drive you nuts if you let it, don't. You can't chase every little thing that most people, other than you, won't even notice.


 

THAT"S what I was getting at earlier:yes:[/quote]

I know, I fully understood your point.:yes:


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## chrisn (Dec 23, 2007)

Just wanted to be clear on that.:wink:


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## jsheridan (Jan 30, 2011)

Roger that.


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## cougar01 (Jan 22, 2009)

OK. Last question. I promise!:yes:

I was out of town for a week on business, and still haven't gone back to do much with the walls. Question is, I have all of the walls primered with drywall primer. I am going to spot spray the white pigmented shellac over the few spots where the primer blistered/bubbled. Of course, will sand the bubbles down first.

I will be topcoating with a satin finish ---- a paint and primer in one (if there is such a thing). From past experience, I will probably end up putting on 2 coats of topcoat since the first coat always looks spotty and like it gets half sucked into the wall to begin with. With the paint and primer in one, is it necessary to still put drywall primer on top of the shellac or can I skip that step and just topcoat over everything? With the "paint and primer in one" ---- and 2 coats of it-----will flashing be a concern at all?


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## jsheridan (Jan 30, 2011)

I would like to say no, but. Your concern would be a shiner. The areas where you spot shellac will be oversealed, less absorptive, relative to the rest of the wall with regular drywall primer. It's possible that after two coats of finish that those spotted areas will have a higher sheen development than the rest of the wall and standout. It's hard to say. I would make uniform the whole wall to be on the safe side. Spot prime, allow the 1-4 four hours dry time and finish. Your here now, there's no going back once the satin is on the wall. Good luck, and when it's done, put the microscope away, lol.


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## cougar01 (Jan 22, 2009)

I GIVE UP! 

No matter where I spot primer with the SW Drywall Primer, the paint is blistering. Some small blisters and some larger ones. I am wondering if I just have way too many coats of primer on, not to mention joint compound skim coats and shellac undercoats, and now the various layers of primer just aren't cured and grabbing hold. 

Should I sand everything back down to as close to the original finish as when I started out, or just sit back and wait about 30 days to allow everything to cure, fix the blistered areas, and cross my fingers and hope that I have seen the last of it. 

The other problem is that I have no idea what type of paint the previous owner had used, and whether they even used a primer. When I took the brackets out of the closets, they had painted AROUND the brackets........meaning they hung the brackets up, then painted the drywall around it when the house was first built. Where the brackets were was still unpainted/bare drywall. I do know that every room had some sort of hideous yellow paint underneath the finish coats.

Other options I am considering is to tear down the drywall and start with new. Or maybe something easier.......permanently lock the bedroom, put up a skull and crossbones, and never go into that part of the house again. :whistling2:


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## tyns (Jul 3, 2012)

*Same Boat*

I just read this thread and I am having the exact same issue except mine escalated to the ceiling even. I tried for weeks to paint a pre-existing painted wall. It is a newer home with latex painted walls. I had several screw pops and a lot of bad clumpy drywalled corners and paint chunks left on the ceiling and walls from the builder. 

I patched all the screw pops with synko joint compound and ran a thin spot prime of behr interior drywall primer over the spots. Several days later I then did a one over priming of the entire room to give a nice "base" to start painting on. On this final coat of priming I started to notice the primer was pin sized blistering around the feathered out edges of the joint compound. I let it dry and cut out the blisters to re patch and re prime those spots. After re-priming the areas, I noticed more blisters around the edges of those spots I just touched up. I am very thorough and I clean and brushed off all surfaces after sanding.

I left the walls and started working on the ceiling. I began painting the ceiling with Behr Ceiling paint and the texture that came off the ceiling paint was atrocious. It caused me to have to skim coat the entire ceiling. Having so many problems with the behr primer on the walls I decided to go out to a paint store and ask their advice. They sent me home with Pratt and Lambert pro hide gold latex primer/sealer and pratt and lambert pro hide gold flat paint for the ceiling. I primed the ceiling with this new primer and it came out beautifully. I then gave the ceiling a coat of the pratt and lambert paint. The first coat had tiny blisters in one spot so I corrected these blisters as I did the wall blisters. I then put on a second coat. My wife was helping watch to make sure no lint or paint chunks were getting left on my roll-outs. Half way through the room, She and I started to panic as we started seeing tons of dime sized blisters forming through out the ceiling. All these blisters are from the primer lifting from the joint compound. 

I let the ceiling dry and began to patch these spots. I have officially given up on trying to do this myself. I have been researching and asking people their thoughts on the situation. From what I am gathering.. Latex Primer is very porous. Any type of new paint or moisture you add on top of the surface will pass through the primer to the subsurface. 

In my case, I suspect that, to solve my problems I need put a base of Oil Primer down to prevent and moisture from getting through to the joint compound layers. Oil primer dries and seals porous surfaces and should completely prevent any blistering from occurring due to the joint compound letting loose from moisture passing through to it. 

On new drywall the joint compound has room to breath behind it. On a previously painted surface, the joint compound just acts as a sponge to hold the moisture from whatever porous surface above it is allowing through.

This is what I gather at least. I am having a painter come and quote the job now though.. I wasted too much time on this. It just bugs me because it is all about using the right product. If the big guns are needed to begin with to do the job right the first time, I would have preferred to have spent a few extra dollars instead of wasting all my time.


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## NicoleA (Dec 13, 2017)

I know this is too little, too late, maybe this will help someone else. but you never want to seal a surface (prime) apply moisture (mud) and then seal it again (prime) it’s like taking a piece of plastic putting water on it and then putting another piece of plastic over it. the moisture has no place to escape and will form a blister under the surface and it will remain in between those two surfaces until those surfaces are removed. If there are imperfections on a wall which has fully cured gloss or semi-gloss paint on it and you are wanting to smooth it out with mud. Just rough up the surface with some 60 grit sandpaper(you don’t have to get every inch of gloss paint sanded but a majority of it helps, at least 50 percent) , remove the dust with a damp rag and apply the mud, let it dry completely, sand it smooth, apply more coats if necessary, and sand those smooth, remove all dust with a dry cloth or vacuum, do not use a wet rag as you will wipe off the mud and Then prime and paint. primer is to seal all the different materials used to smooth or texture a wall and allow the paint to sit evenly on top of them. It is made to stick to a surface and then for paint to stick to it. not mud or wall paper or and anything with moisture, period. Seal after all surfaces are the way you want them and right before you paint


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## mark sr (Jun 13, 2017)

> you never want to seal a surface (prime) apply moisture (mud) and then seal it again (prime)


I disagree, while primer isn't normally needed under joint compound there are times that it is. Skim coating a wall that has torn paper [exposed gypsum] is one such example. Joint compound should always be primed before paint is applied.


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## chrisn (Dec 23, 2007)

Most primers don't "seal" the wall anyway


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## woodco (Jun 11, 2017)

I think it goes without saying that you dont prime over mud that isnt fully dry.

Also 60 grit is WAY too course....


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## NicoleA (Dec 13, 2017)

Please disregard my original statement. It is incorrect.


I just realized that I should be taking lessons and not trying to teach them!
I had paint blister on me only once , for the first time this past weekend, So I’ll just shut up cuz, i don’t know it all. 
What I should have done is came before it happened, in order to prevent it, rather than after
it happened, to find out how to fix it.......��


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## mark sr (Jun 13, 2017)

That is part of how we learn! as long as you don't keep repeating the same mistakes you are doing good ...... and forums like this one help us do a better job on the things we aren't proficient at.


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## woodco (Jun 11, 2017)

I dont think think the OP actually figured out the cause of his blisters. It didnt sound like it a moisture issue.


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