When you mix paint, one of the things you might end up having to do is mix paint with a joint compound for the purpose of creating a plaster effect on a wall. There are two ways you can do this, although they do require some experimentation to get the right texture and color for your needs.
The most important thing to note for this process is that you can only mix the joint compound with latex paint. Don’t attempt it with oil-based paint because the two will not combine. Be aware of this when you go shopping for the paint color you want.
You can use a joint compound that’s pre-mixed and available in tubs or you can also make your own by adding a powered joint compound to water.
If you use the pre-mixed joint compound, you’ll need to thin it a little before you add it to the paint. There’s no set degree for how much you can thin the joint compound as it ultimately depends on the final effect you want to achieve. The best answer is to just thin it a little, then experiment as you continue to mix your paint.
Start by pouring the paint into a large bucket. Add a little of the joint compound at a time and mix it in thoroughly using a drill with a mixer attachment. What you’re really looking for is something with the consistency of cake or brownie batter. This will help the material spread and adhere to the wall properly. It is important to note that you’ll need the paint to be thinner if you're applying it with a brush or roller than you would for applying with a trowel.
One problem you might face is that the joint compound is going to affect the color of the paint and lighten it. As a result, it is recommended that you buy a darker shade of the color you want. Unfortunately, this isn’t an exact science or formula, so it can take quite a bit of trial and error in order to achieve both the consistency and color you want for the final look.
Try an Alternative Method
If you are having trouble getting acceptable results by adding the joint compound to your paint, you can try adding powdered paint to the joint compound instead. To mix the material this way, pour some of the thinned compound into a large bucket. Then, add some of the powdered paint in the color you want. Mix them together with the mixer attachment on a drill. It can be a little trickier to achieve the right consistency this way, and you’ll still need to experiment to find the right shade of color, however, this method does make it a little easier to control your final color.
Whichever method you use, be prepared to make several attempts before you find the right result. It’s worthwhile making notes each time - this way, when you succeed in finding the ideal medium, you’ll know how to do it again.