5 Tips for Thinning Water Based Paint

Latex or water based paint is often used to paint interior walls or furnishing that are not exposed to the elements. Latex paints can thicken sometimes and may need to be thinned out before they can be used. Follow the tips below to make thinning water based paint a little easier.

Avoid Leaving the Paint Can Open

One of the easiest ways to avoid thickening of your latex water-based paint is to simply close the lid on the can when you finish pouring paint into a bucket or roller pan. Leaving the lid off of the paint can too long will allow moisture to evaporate from the paint, which will in turn make it thicker. So, as soon as you pour your paint, close the paint can.

TIP:Doityourself’s painting consultant Edward Kimble, author of Interior House Painting Blog, suggests, “Also, a slight covering of water on the surface of the paint is great for keeping the paint from thickening too much. Pour a small amount of water very slowly on top of the paint in the can. If you pour it in too fast, it will just mix with the paint.”

Don't Store Latex Paint Too Long

If possible, try to avoid storing latex paint too long. Over time, water based paint will begin to thicken and its consistency will become much harder and even putty like in texture.

Keep Stirring

When allowed to sit for a long time, latex paint will decant, with the heavier particles settling to the bottom. Before trying to thin the paint, stir, stir, and then stir some more. The more you stir your water based paint, the smoother it becomes. If you have a drill, consider purchasing a paint mixer extension to make the process easier and more efficient. The electric drill stirring rod is very sharp. Insert or remove the stirring attachment with the electric drill unplugged.

When stirring your paint, keep in mind that stirring the paint for only a minute or so usually won't mix the paint well. If you're stirring the paint by hand, stir the paint continuously for at least 5 or 10 minutes.

TIP:Edward adds, “Stir in an upward and downward spiral motion. However, the best way to thin and stir latex paint is to pour the paint back and forth between two paint cans. When using more than one gallon of a custom color, pour paint back and forth repeatedly, as color can vary slightly from can to can. This is called ‘boxing’ the paint.”

Use Water to Thin Water Based Paint

If you do need to add liquid to your water based paint to thin it out, try water before adding anything else. If a new can of paint is thicker than you would like, add an ounce or two of water and then thoroughly stir the paint.

Continue to add water in small increments until the desired consistency is achieved. If you add too much water at the start, you will find that a lot of time will be needed to thoroughly mix the paint. So, remember: add a little, then stir a little. Continue the process until the paint is just right.

Use a Commercial Thinning Additive

There are several different commercial products available for thinning a water based paint. If you look in the paint section, of a local home improvement store, you will find products that can be added to water based paint. These commercial additives are advertised to help to thin the paint, and also act as a paint conditioner, making paint easier to apply and helping to remove unsightly brush marks. Although these types of commercial additives can be effective, they are also expensive. So, try adding water first.

TIP:Edward says, “These products are expensive and unnecessary. Tap water works fine. Also, once such additives are put into a can of latex paint, the paint has a very short shelf life.”

Edward Kimble, professional painter and author of Interior House Painting Blog, contributed to this article.