# joint topping compound bubbles after applying to wall



## Nestor_Kelebay (Jun 17, 2008)

Gordy:

Those air bubbles don't form once the joint compound is on the wall as you're presuming; they're already formed in your mixing container because you're mixing the stuff way too thick.

No one wants to pay for transporting water, so premixed joint compounds come so thick in the box or bucket that you need the arms and wrists of a Mountain Gorilla to use the stuff the way it comes. Mix some water into your joint compound and not only will it be easier to spread, the air will bubble out of it before you start spreading it on the wall.


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## oh'mike (Sep 18, 2009)

Explain in more detail,please.

As Nestor mentioned, mixing the mud with a whip and drill helps---However, for some reason ,I have found that topping compound (blue lid) will some times bubble when applied over painted drywall---I don't know why--and it doesn't happen frequently--but it does happen ,even when the mud is mixed in the usual way---


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## Nestor_Kelebay (Jun 17, 2008)

Here, do this:

Go to some of the places that repair small appliances in your town and ask them if they're going to be throwing away any electric hand mixer blades, to throw them your way:










Electric hand mixer blades have slots cut into the ends of the blades, and those slots can wear out, thereby preventing the blade from working properly in the mixer. However, those same worn out blades can be mounted in the chuck of a 3/8" drill to make a perfectly good drywall joint compound mixer for a DIY'er. If there's anything on the end of the blade that will interfere with you're mounting it in a drill, just clean it off with a file.

Use a pair of pliers to bend the ends of the blade outward so that they'll get into the corners of a large metal soup can.

Now, mount that modified kitchen mixer blade in the chuck of a 3/8 inch drill, and use that as a mixer for mixing water into your joint compound.

Do your mixing inside a cardboard box so that when you pull the spilling mixer blade out of the mixing container, you get joint compound spattering all over the inside of the box, instead of all over your workspace.

Be careful cuz that thing can break a finger or scrape the skin off of it if you're not careful. Wait for the blade to come to a full stop before mucking with it.

The garbage cans around your local 7-11 will be full of Big Gulp, Super Big Gulp and Double Gulp cups that make great mixing containers. Double the cup up for better protection against the blade cutting through the side of the cup.

(I bought a cheap B&D electric drill at a yard sale for $10 and just kept the mixer blade in it all the time for mixing joint compound, base coat plaster, floor leveler, brick mortar, everything I needed to mix with water.)


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## Fix'n it (Mar 12, 2012)

i must be a Mountain Gorilla , as i have used it that way. but, as was said, the stuff works way better if you mix in some water. what i find pretty easy = i use a paint scraper to mix in water to the top 2-3" in the bucket. it doesn't take much effort. this same scraper is what i use to transfer the mud to my hawk.


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## gordy32 (Mar 18, 2015)

Thanks all for your quick replies! I'll try thinning the mud some more, and I think I may have been applying the mud a little too thick. 
And why does my location have any bearing on the issue? 

Chico, CA


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## Fix'n it (Mar 12, 2012)

gordy32 said:


> And why does my location have any bearing on the issue?
> 
> Chico, CA


in this case, i don't think it does. but there are many cases where it makes a massive difference.


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## oh'mike (Sep 18, 2009)

Your location is not important for this question--The 'location' notice is in my signature line and appears in all of my posts----Mike----


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## ToolSeeker (Sep 19, 2012)

A lot of times mixing the mud at a high speed puts too much air in it and will cause bubbles. Some say it works some say it doesn't but a squirt of dish soap seems to help with the bubbles. I've used it for many years and to me it seems to work.


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## ToolSeeker (Sep 19, 2012)

A lot of times mixing the mud at a high speed puts too much air in it and will cause bubbles. Some say it works some say it doesn't but a squirt of dish soap seems to help with the bubbles. I've used it for many years and to me it seems to work.

One reason it bubbles over paint is the moisture in the compound can't soak into the substrate so it leeches out the surface this causes the bubbles.


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## Islander26 (Mar 17, 2015)

Drywall compound also* "gases".*

If you put regular compound over a slick surface "like paint". It will bubble a little to the surface. If you put regular compound over wet hot mud, it will bubble as well. Regular compound needs to dry to the air, and to the surface it is applied to. If one side is blocking the "off gassing"....the bubbles will form.

It's nothing unusual. 

A tight skim after it dries will take care of it.


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## Nestor_Kelebay (Jun 17, 2008)

Islander26 said:


> Drywall compound also* "gases".*
> 
> If you put regular compound over a slick surface "like paint". It will bubble a little to the surface. If you put regular compound over wet hot mud, it will bubble as well. Regular compound needs to dry to the air, and to the surface it is applied to. If one side is blocking the "off gassing"....the bubbles will form.
> 
> ...


What is this "bubbling"? What gas is produced by the joint compound that causes bubbles to form in the joint compound, and how does this gas supposedly form. I've read the mixing instructions on the bag of Synko ProSet 90 joint compound that I use, and no where does it tell me that the result of mixing that powder with water will be the creation and liberation of any kind of gas. Do the instructions on a box or pail of premix joint compound say anything about off gassing?

I've Googled "Drywall Joint Compound off gassing" and all I got was another question about bubbles in drywall joint compound in this same very web site.
http://www.diychatroom.com/f101/mud-paint-offgassing-help-174997/

If drywall joint compounds actually did offgas, there would be tons of credible web pages on the internet saying how that gas forms. But, Goggle can't find any such web sites.

Here's as far as I can let my imagination run wild:
If you tint paint quite a bit in the paint tinting machine when you buy it, then you're introducing a lot of glycerine into your paint. They use glycerine as the carrier fluid for paint colourants because it's equally soluble in both water and mineral spirits so that the same colourants can be used to tint both latex and oil based paints and primers. Now, glycerine is ALSO the slowest additive to evaporate out of the paint, often taking up to a month to completely evaporate under cool conditions, but normally it evaporates within a few days.

That glycerine evaporates from the paint or primer as a vapour and, if you let your imagination run wild, could be imagined to cause bubbles in the joint compound that's spread over fairly new primer or paint. But, that's gotta be a wild stretch. Glycerine is soluble in water, and so the most you'd ever expect is that the glycerine would dissolve in any wet joint compound spread over the paint.

Can anyone tell me what gas is produced by drywall joint compound or even link to a credible web site that claims that off gassing happens? If not, then I'm gonna put joint compound off gassing in the same bag as crop circles, Bigfoot. the Burmuda triangle and that thing that crashed in Roswell unless and until I see some kinda credible proof it happens.


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## Islander26 (Mar 17, 2015)

Nestor_Kelebay said:


> What is this "bubbling"? What gas is produced by the joint compound that causes bubbles to form in the joint compound, and how does this gas supposedly form. I've read the mixing instructions on the bag of Synko ProSet 90 joint compound that I use, and no where does it tell me that the result of mixing that powder with water will be the creation and liberation of any kind of gas. Do the instructions on a box or pail of premix joint compound say anything about off gassing?
> 
> I've Googled "Drywall Joint Compound off gassing" and all I got was another question about bubbles in drywall joint compound in this same very web site.
> http://www.diychatroom.com/f101/mud-paint-offgassing-help-174997/
> ...


Since you where kind enough not to be "smug". :wink: 

As water evaporates, it is turned into a gas. 

The compound exposed to the air will harden before the compound adjacent to substrate. The trapped water in the compound will form into trapped bubbles.

You could call USG and have them explain it to you, but it is pretty basic stuff.

Respectfully...... 

Bigfoot


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## Nestor_Kelebay (Jun 17, 2008)

Islander26 said:


> Since you where kind enough not to be "smug". :wink:
> 
> As water evaporates, it is turned into a gas.
> 
> The compound exposed to the air will harden before the compound adjacent to substrate. The trapped water in the compound will form into trapped bubbles.


Yes, but if what you're saying is true, then all of us would see bubbles of water vapour coming to the surface in our joint compound all of the time.

But we don't. It's the fairly rare exception rather than the rule.

If it was water vapour, it would be the rule. And, Google would find all kinds of web sites explaining the phenomenon. But, Google "Drywall Joint Compound Off Gassing" and you find nothing.

It can't be both common and yet there not be any reference to it on the internet.


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## Islander26 (Mar 17, 2015)

Nestor_Kelebay said:


> Yes, but if what you're saying is true, then all of us would see bubbles of water vapour coming to the surface in our joint compound all of the time.
> 
> But we don't. It's the fairly rare exception rather than the rule.
> 
> ...


As a former estimator with a large drywall company, I had to sit through many boring "REP" meetings with USG, and other vendors that we sourced through.

I had asked the particular question on bubbles........along with hundreds of others. His response was pretty much in line with what I gave you. The bubbles that you see in a new bucket of mud is a result of moisture turning into little pockets of gas. The plastic sheet that you see when you open a bucket of mud is to help keep the moisture in the mud. The moisture can and will turn into little pockets of gas. Some buckets will have more bubbles than other at times because of a variety of reasons......like being in a hot semi trailer for a few days, warm storage, etc. etc. Compound will also react many similar ways on application, depending on substate absorption, air temps, and humidty.

The water also reacts to certain thickening and binding agents like starch

The term off gassing, although not commonly used in construction, is nothing more than a chemical going from solid wet state.... to gaseous state.


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## Vigor (Jul 26, 2017)

I haven't done a whole lot of drywall but I have had a lot of problems with bubbling and have been seeking an answer to why.

Evaporation doesn't seem to be a plausible theory because water wouldn't evaporate fast enough to cause a bubble. One bubble might represent thousands of air molecules. I can watch the bubbles form right before my eyes. If evaporation was the cause, it would happen to everyone.

I think I have a better theory.

I think drywall dust particles have pockets of air amongst them. I think they would have to, considering they are not bound together, so something must fill the gap between them. Once new mud is applied over dust, it adds a slight amount of weight, compressing the dust particles and forcing the air out. Mud that is too dry makes it difficult for that air to escape. Mud that is more wet allows air to escape easily and absorbs the dust particles more easily. 

I have observed I get more mud bubbles when I forget to clean the dust off before applying another coat of mud or don't do a good job of cleaning dust off.

I have observed I can work bubbles out by working the mud around on the wall.

I have never watered down mud, I just use it in the consistency I purchased it in.

So, I did an experiment. I watered down some mud and applied it to a section of wall I had just sanded, but needed a new layer of mud. The wall was pretty dusty, the watered down mud still got a few bubbles, but they worked out pretty easily.


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