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Pits in drywall mud

Drywallisit's picture

Hi folks, I have a perplexing little problem that I need your input on.


I have been a drywall contractor since 1992 and have one problem that I have not been able to solve - it is the following:


When I am tying new drywall into a previous wall, either drywall or plaster and  previously painted, and am in the taping/fill stages, I have an ongoing problem with small bubbles/pits. I have thinned my mud and have reduced mixing speed to lessen the introduction of air in the mixture, but it does not eliminate the problem. Sometimes the pitting is severe enough that I cannot eliminate it at the mud stage and have to wait until the wall is primed before I can go back in and fill the pits to get a good finish. Priming the wall seems to stabilize the pits so they can be filled.


Any thoughts/tips/tricks on how this can be eliminated at the taping/fill stages?


Thanks

(post #108035, reply #1 of 29)

Try a squirt of kitchen dish soap or a product called "No Pock" (which appears to be a dish-soap like material) mixed into your mud. It has helped to eliminate those pits when I've used it.

Good luck,

DIA

(post #108035, reply #2 of 29)

Great, thanks for the tip. I had heard that dishsoap worked but was afraid that it would interfere with the paint coat.


Where did you buy the 'No Pock' ?


 


Regards


drywallsit

(post #108035, reply #3 of 29)

You can also use mud  max from trim-tex .

(post #108035, reply #4 of 29)

The active ingredient in soap and those additives is glycerin.
It may reduce pittin', but it won't eliminate it.
Nothin' will - that's just how it is.

Hard work is damn near as overrated as monogamy.
- Huey Long

_________________________________________________

(post #108035, reply #8 of 29)

I've seen it at some supply houses and also at Menards. HD has never carried it around here.

This place could use a good coat of fire.

(post #108035, reply #5 of 29)

When I started doing drywall work I never got any pits, but now I do.  I realized that I move my knife a lot faster than I used to and that seems to cause more pits.


On those occasions when I move my knife slower (like when I'm trying to avoid even the final sanding) I seem to get many fewer pits.


And yeah, soap and water help, but I'm not sure which helps more because I usually add both if I add either.

(post #108035, reply #6 of 29)

I have been having more and more problems with bubbles.

I think it is a Sheetrock brand problem more than anything.

Recently started using mud from local Carter Lumber store and do not have the problems. Buckets are marketed as Carter Store brand but I know it is made by someone else. It is alot smoother. Only problem I have is it smells sour.

After setting in the bucket overnight it gets an oily liquid on it so you have to respin it. Lanolin?

I do like it even with the smell.

(post #108035, reply #11 of 29)

I agree with Huntdoctor on the Sheetrock brand. I had all kinds of pock problems when I picked up a bucket of that brand. I didn't want to waste it, so I topped the pocks with a thin skim of, I think, DAP before sanding.

(post #108035, reply #7 of 29)

common problem when you're going over painted surfaces. The painted surface is not porous like unfinished drywall and when the water evaporates out of the mud it has to come out somewhere.

With new drywall, it dissipates into the paper but on painted surfaces it is forced to "outgas" through the front causing little craters.

A few different ways to deal with it with varying results

sand the finished area with 80 grit to open it up

prime the wall before drywalling

thinner coats of mud

and the one I have most consistent results is using hot mud, preferably brown bag for the first coat

YMMV

Barry E-Remodeler

 


Barry E-Remodeler  

(post #108035, reply #13 of 29)

BarryE,

You answered the question correctly!

(post #108035, reply #16 of 29)

At least 3 of us know it.

Barry E-Remodeler

 


Barry E-Remodeler  

(post #108035, reply #18 of 29)

Yea..not to many people are experts in drywall.

(post #108035, reply #19 of 29)

"The painted surface is not porous like unfinished drywall and when the water evaporates out of the mud it has to come out somewhere."

"prime the wall before drywalling"

I'm confused. Primer is paint, so how does that help?

BruceT
BruceT

(post #108035, reply #20 of 29)

Primer is not paint. He meant to say prime the drywall before finishing it.

(post #108035, reply #21 of 29)

Primer is most certainly paint, specifically formulated for best adhesion and to seal porous substrates so they won't show through as dull areas in the topcoat.

BarryE said that painted surfaces were not porous like the paper on new drywall, so water has to "outgas" and therefor causes pitting. That's why I don't understand how rendering the new drywall non-porous wouldn't also cause pin holes.

BruceT
BruceT

(post #108035, reply #22 of 29)

I didn't say that every method i listed worked best for everything

As far as paint and primer being the same, Are you saying the porosity is the same for semi gloss latex acrylic as it is for PVA primer?

I don't think so. This has been debated a few times before. Paint and primer are 2 different animals

Barry E-Remodeler

 


Barry E-Remodeler  

(post #108035, reply #23 of 29)

"I didn't say that every method i listed worked best for everything"
Maybe I misread your post. Since the subject was pin holes, I thought you were saying that primer would prevent pin holes.

"Are you saying the porosity is the same for semi gloss latex acrylic as it is for PVA primer?"
Probably not the same, but PVA is non-porous enough that semi gloss acrylic paint over it will not soak into drywall paper or drywall compound and thereby lose its gloss.

"Paint and primer are 2 different animals"
Having worked in the paint industry for many years, I would say that topcoats and primers are different kinds of paints, but both consist of binders, pigments, solvents and diluents, so they are both paints.

BruceT
BruceT

(post #108035, reply #24 of 29)

I think I was saying that primer has been used with varying results. It would not be my first choice, but I've seen it used. Like Zano said 1 coat primer over new wallboard will not cause pinholes like multiple topcoats over old board or plaster.

"Having worked in the paint industry for many years, I would say that topcoats and primers are different kinds of paints, but both consist of binders, pigments, solvents and diluents, so they are both paints."

Now we are in the realm of semantics, but I'll give you that one :) In most cases the pigments and additives, as well as the amount of binders are different between primers and "topcoats".

I do know as someone who's been in the production end of painting for many years, that the paint stores are confused when I go in and ask for "paint" <g>

Barry E-Remodeler

 


Barry E-Remodeler  

(post #108035, reply #28 of 29)

I wonder if the problem revolves around oxidation of the painted surface?


I have touched up walls that have been recently painted and the pitting is less of a problem. Yet if I go and try and tie into a wall that was painted a few months/years ago the pitting problem is much worse. There seems to be a chemical reaction between the mud and the painted surface.


Pitting always seems worse for 2nd and 3rd coats than is the case with tape coat.


 


I appreciate all the feedback that I am receiving from everyone - sure seems to be a common problem.


 

(post #108035, reply #29 of 29)

"I wonder if the problem revolves around oxidation of the painted surface? "

I don't think it's oxidition. Could be a combo of things contamination...grease, cleaners etc and paint cure

Latex paint is dry to the touch in short time, but it takes at least 30 days to fully cure. gives it a harder shell so to speak

then when your talking years you are usually talking more coats of paint, harder to penetrate

Barry E-Remodeler

 


Barry E-Remodeler  

(post #108035, reply #25 of 29)

Barry E. is correct.  I had this problem years ago.  I hate to admit it but maybe 30 years ago.  It was really frustrating.  I started priming the "old work" with Bin before I started to make the blend.  No problem after I primed with Bin.  The more things change the more they stay the same.  Mike L.

(post #108035, reply #26 of 29)

And a coat of primer was preferable to you rather than another coat of mud? sheesh!

Hard work is damn near as overrated as monogamy.
- Huey Long

_________________________________________________

(post #108035, reply #27 of 29)

Yup!

(post #108035, reply #9 of 29)

Drywall


Ditto what Barry E said. I only have in when I am taping into old painted plaster.


Or any old painted surface.


Rich

(post #108035, reply #10 of 29)

I used to only have the problem when mudding over painted surfaces but lately I have been having the problem over all surfaces.

With the Carter mud no bubbles, not even over painted surfaces.

I think it's a mud problem.

(post #108035, reply #12 of 29)

You've got bubble farms. We get those too. Sometimes its easier to just fill after priming. I havent found any other solution.

 


Family.....They're always there when they need you.

 

Family.....They're always there when they need you.

(post #108035, reply #14 of 29)

I have painted and gone back to do the final. I know that in high production that wouldn't work. Just saying I've done it.


Also, it seems like more defects always show up after paint ;^)


Edited 3/20/2009 12:37 am ET by popawheelie

______________________________________________________________ ______________________________________________________________ There are three kinds of men: The one that learns by reading, the few who learn by observation and the rest of them have to pee on the electric fence for themselves. Will Rogers

(post #108035, reply #15 of 29)

Thanks for the feedback.


Interesting to note that this is a common problem and no one seems to have found a complete solution - perhaps a business opportunity - hmmm.

(post #108035, reply #17 of 29)

Well for connecting to plaster, stick with real plaster.

I don't have a lot of experience, but I will say that I use fiberglass tape when connecting to a previously finished surface. Paper tape is great on unfinished drywall, but seem to have more problems with air bubbles or not adhering to finished surfaces.

And priming previously finished surfaces before taping seems to help.