avoiding bubbles in joint compound

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DanielG
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avoiding bubbles in joint compound

Post by DanielG » Fri Aug 02, 2019 7:29 am

Hi all,

I was wondering if anyone would know how to prevent bubbles from appearing in joint compound. I'm not talking about small bubbles that may appear in drywall tape, but when spreading mud over a joint. After the mud dries, small pock marks; or craters, are left- which are impossible to sand out.

I know that sometimes bubbles form in joint compound if it is applied on top of totally non-absorbant surface. (in my situation it was a second coat of mud on top of sheet rock...)

I had mixed my compound with a paddle drill- could I have mixed to fast? Or put too much water in? Any suggestions would be greatly appreciated!

Thanks
Dan

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Aaron
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Re: avoiding bubbles in joint compound

Post by Aaron » Fri Aug 02, 2019 11:44 pm

A technique you may try is to make a water-glue solution, and use that solution with additional water to mix up quick-set mud. To make a liter of the solution, just find an empty plastic liter bottle and add about 200 ml of standard white PVA glue (Elmer's, Weldbond, etc.), and fill the rest with water. Shake the bottle very vigorously until it looks like milk.

Then when you mix up quick-set mud, put as much of the glue-water solution in the trough as regular water. The idea is to have about a 1:10 ratio of glue to water. This will really boost the adhesion of mud to any surface and it's also excellent for the first paper taping.

Subsequent coats of mud can just be the bucketed joint compound. Always go for the lightweight kind. It's good to mix it up with a paddle but not too much. Add only enough water so it's sort of like yogurt, and spread it tightly with a broad knife without overworking it.

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A. Spruce
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Re: avoiding bubbles in joint compound

Post by A. Spruce » Sat Aug 03, 2019 12:13 am

I think I understand what Aaron is trying to say, but I do not recommend his methodology.

I've been doing drywall for the better part of 30 years, while I'm certainly no "expert", I do know my way around a pan of mud. In my experience, bubbles, and the voids they cause, are due to the mud itself being too thick when applied and possibly the application being too thick.

1 - Always always always, cream your mud before applying it.
2 - 9 times out of 10, premixed mud is way too thick straight out of the container, it needs to be thinned with a little bit of water.
3 - Properly thinned and creamed mud has the consistency of thick pancake batter, it won't run by itself, but, it will smear and tool with ease.
4 - Creaming mud can be done with a wand and drill or by the pan full with a drywall knife. Either way, you're looking for a smooth consistency, void of lumps and bumps, and you want it to hold a bead on the edge of the knife without sagging.

With your mud consistency sorted, you never want to apply more than 1/8" of mud at a time and never more than 1/4" total thickness, or you're going to have bubbling and cracking problems. If you ever have to apply more than 1/4" of mud, then you need to stop and readdress the hanging of the drywall itself.
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Shannon
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Re: avoiding bubbles in joint compound

Post by Shannon » Sat Aug 03, 2019 4:44 pm

Never heard of Aarons solution so can't say if that works or not but thinner coats is usually the best solution. If you are mudding over a previously painted wall you will get them every time. Adding a bit of Dawn or Joy liquid dish soap to the mix is supposed to help and I've had varying degrees of success with those. By a bit I mean like 3-6 drops per large pail of mud.
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DanielG
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Re: avoiding bubbles in joint compound

Post by DanielG » Sat Aug 03, 2019 4:56 pm

Thank you guys for the very helpful advice! Very much appreciated!

Clarence
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Re: avoiding bubbles in joint compound

Post by Clarence » Mon Aug 05, 2019 9:59 am

I don't do drywall but have used the Joint compounds before.
The tech data sheet STATES " DO NOT MIX WITH ANY OTHER MATERIAL "
Yes I have & still do add other plaster products with ALL PORPOSE Joint compound & it works better than the straight compound plus with my additive you can trowel it smooth & no sanding required.

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Shannon
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Re: avoiding bubbles in joint compound

Post by Shannon » Mon Aug 05, 2019 12:51 pm

What do you add Clarence?
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Clarence
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Re: avoiding bubbles in joint compound

Post by Clarence » Mon Aug 05, 2019 3:18 pm

What I add depends on what type of repair & how large it is.
Some examples of an additive.
USG Diamond finish Plaster.
USG Gauging Plaster
Sifted USG Structo-Lite Plaster.
For a higher PSI rating add USH Hydro-Cal Cement Plaster.
For very quick set Moulding Plaster OR Hydro - Cal Plaster.
Keep in mind that Joint Compound is Attapulgite Clay or Kaolin Clay these are minerals all the above are also minerals & mix very well with each other.

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Shannon
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Re: avoiding bubbles in joint compound

Post by Shannon » Mon Aug 05, 2019 11:04 pm

plaster is not something done around here much at all so these items are likely not easily available in my area but I'm always interested in products and additives.
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