How to Thin Latex Paint

Sometimes latex paint can grow thick from either sitting too long in the open air or through disuse. Knowing how to thin it again can save you money over buying a whole new can. Luckily, thinning latex paint is easy. All you need is water and several clean, empty, gallon cans.

Step 1 – Determine Whether Your Paint Requires Thinning

Not all latex paint needs to be thinned. Before proceeding with the thinning process, administer a quick test to determine if it is necessary. Insert a stirring tool into the paint can. After letting it sit for a few moments, pull it out, taking care to keep it positioned above the paint can to prevent any paint from getting on the floor. If the paint drips off the stirring tool in a smooth and even fashion, the latex paint does not require thinning. In fact, any attempt to thin such paint is likely to render it unusable. However, if the paint sticks to the stirring tool or gives off a clumpy appearance, proceed with the thinning process.

Step 2 - Apply Water to the Paint

Having determined that your latex paint is in need of thinning, you are ready to begin. Instead of using a stirring stick, do it the way that pros do it. Take one gallon of paint, and one empty gallon can. Fill the empty gallon can with 1/2 can of water, and pour the paint and water back and forth. Add another 1/2 gallon, more or less, and pour the paint and water back and forth from can to can.

Water can also be added when “boxing” several gallons of tinted paint to achieve the same color and consistency in every can.

Step 3 – Use a Commercial Thinner

If the previous technique hasn’t given you the consistency you want, there is fortunately still another option. Commercial thinners are easy to use if you follow the instructions on the container, but make sure you work in a well-ventilated area and wear protective gear to keep from inhaling too many noxious fumes.

The downside to using paint thinner is that it’s not only the pricier solution, but paint that’s been mixed with thinner has a shorter shelf life than paint thinned with water.

Tip: When closing a can of latex paint to store it, first pour a very small quantity of water over the surface of the paint. Don’t shake the can or mix it in. The water surface will keep the latex from forming a solid skin on the top of the paint.

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