Skip to Content

How Can I Keep Bubbles Out of My Drywall Mud?

Bubbles forming out on a painted wall.

The U.S. Gypsum Company first developed sheetrock back in 1916, and contractors have been fighting bubbles in their drywall mud ever since. Commonly referred to as joint compound, drywall mud is a porous substance that allows air to pass through it.

If air cannot pass through it, bubbles may form on top of the compound. Here are some of the most common reasons why this happens, as well as some practical solutions.  

Related To: How to Clean Drywall

1. Problems with the Joint Compound Itself

A can of ready to use drywall compound.

Drywall mud comes in either a pre-mixed version or a dry powder that you must add water to. When mixing your own compound, getting the right ratio of water to powder is essential. Furthermore, getting everything mixed properly is also crucial.

That’s why many experienced contractors recommend stirring joint compound very thoroughly, even if you are using a pre-mixed variety. Some even claim that adding a few drops of dish detergent is helpful too. 

You may also experience problems when using very old drywall mud. Ideally, joint compound should be used within 9 months to one year after being opened, provided it is stored correctly. In addition, manufacturers will place a sticker with an expiration date on each container sold.

It can be tempting to use joint compound even after its expiration date, but you are much more likely to experience bubbles if you do.

Sheetrock Lightweight Joint Compound- 90 4 Lb Sand 85 - 130 Min

In some cases, even brand new compound can be faulty. This could be due to problems during the manufacturing process or because it was stored incorrectly at a warehouse or home improvement center.

Joint compound may sometimes dry out, particularly if you leave the lid off. Dry joint compound will not stick properly, in which case you are likely to notice bubbles. Adding a bit of water can sometimes bring the product back to life, so long as it is still within its usefulness date.

For best results, add just a bit of water, stir thoroughly, then add in a little more if needed. When drywall mud is the right consistency, it will somewhat resemble cake frosting.

2. Placing Mud Over a Painted Surface

Like joint compound, fresh drywall is also very porous. However, once it’s been painted, the surface is then sealed and will not allow air and water to pass through. Some bubbling is therefore inevitable, particularly if your walls have glossy or semi-gloss paint.

LEVEL5 12" x 4.75" 0.7 MM Flat Drywall Trowel | Triple-Hardened Stainless Steel, High-Impact Handle | Sheetrock Gyprock Wall-Board Plasterboard | 4-961

As the Hammer Addict explains, getting rid of bubbles on painted surfaces generally requires at least three coats of mud. Check for bubbles after your initial application, then skim tightly over any that are present. Hold your trowel at a 45-degree angle and attempt to remove as many bubbles as possible. Move up and down as well as from side to side while keeping firm pressure on your trowel.

Chances are you will still see the tape once you have finished with the first layer of drywall mud. Accordingly, you must allow it to completely dry and then repeat the process until there are no more bubbles and your joint has a neat, even appearance. 

3. Improper Tape Application

A person applying tape on a wall.

Most drywall tape is a mesh-like product that will allow joint compound to seep through. To apply this tape, you will first add a layer of drywall mud, followed by the tape and then another application of compound. You must apply the correct amount of pressure when securing the tape; otherwise, it will not stick correctly and bubbles will form underneath.

Some do-it-yourselfers opt for a paper drywall tape instead. This tape comes in a single layer without any holes for the drywall mud to seep through. Accordingly, if it isn’t placed smoothly, you might notice bubbles in certain sections.

Bubbles that form over the top of tape can sometimes be smoothed out with a trowel. As with painted walls, this can require up to three coats of drywall mud. If you are still seeing bubbles after the third layer of compound, you should remove the tape completely and start over. 

4. Wrong Amount of Drywall Compound

A person mixing a drywall mud using pallet.

Pay close attention to the amount of joint compound you are using when placing your first layer inside the seams. Not enough drywall mud leaves gaps where air pockets (and bubbles) can form. Even so, that doesn’t necessarily mean that more compound is better. In fact, too much can cause the same problem, because the tape won’t be able to stick properly.

When adding drywall mud, a common problem people have is pushing out too much of the joint compound from underneath the tape. This has the same effect as if you failed to add enough drywall mud in the first place. 

To counteract this problem, add a thin, even layer of drywall mud. Maintain consistent pressure with your trowel and avoid the urge to press down too hard. Ensure each layer has ample time to dry before adding the next one. Light sanding in between layers is often helpful, as well. 

Learning how to apply drywall mud is something of an art. As such, beginners are more likely to have problems adding too much or too little compound. As you become more experienced, you’ll have a much better feel for how much drywall mud to use. 

5. The Surface is Dirty or Wet

A person cleaning the wall using a map.

When applying sheetrock compound, always begin with a clean, dry surface. That way, your tape and drywall mud is more likely to stick evenly. Do not wash down fresh drywall-just give it a light dusting with a lint-free cloth or dust mop instead. 

On the other hand, washing the walls with warm, soapy water is recommended if they have already been painted over. Just be sure to let them dry completely before adding any compound.

Preventing Bubbles: The Bottom Line

A worker wearing eye goggles while applying drywall mud.

Even the most proficient drywall contractors still have issues with bubbling compound from time to time. Consequently, you shouldn’t feel too bad if you have problems with it also. After reading this article, you should have a better idea as to what causes bubbles in drywall mud as well as the steps you can take to minimize them. Keep these things in mind and you too can experience perfectly finished walls.