How to Avoid Bubbles in Joint Compound

Clean the length and width of the crack. Use the sandpaper to remove the rough edges from the side of the crack. You can use the putty knife to remove the extra debris in the crack, which can cause bubbling and cracking. You can use the edge of the putty knife for this.

Mix the joint compound with a butter knife or 1/2-inch dowel rod. If you are using a base, follow the directions for your specific package since all brands are not the same. It is better to have it too thick then having to add more mix to thicken it. As it sits over time, it will dry out, and mixing it will make it into a paste again. It is also a good idea to keep it at room temperature since this will also eliminate the bubbling problem. The desired thickness is that of toothpaste.

Apply the joint compound with the putty knife. Make sure that you are forcing it firmly into the crack. This will help eliminate the bubbles. Feather the compound out to the original flat surface of the wall. Again make sure that you are pushing firmly with the tip of the blade.

Allow the compound to dry. Use the sandpaper to smooth out the joint compound. This will need to be brought to a smooth level with the original skim coat or plaster. Then apply another thin coat of joint compound over the original compound. Allow to dry then sand and feather once more.