What Can You Use to Thin Interior Latex Semi-Gloss Paint?

Shot Glass Method

• There's a lot of water in the typical gallon of latex paint, and if the can is left open long enough some of that water will evaporate, resulting in paint that is too thick to apply smoothly. To avoid over-thinning, add one shot glass of water at a time, then stir the paint with a paint paddle. Stop adding water when the desired viscosity or thickness is achieved.

Estimating the Right Amount of Water

• A pro painter determines proper thickness by using a device called a viscosity cup, an inexpensive device available at most paint stores. You may achieve similar results by observing how paint flows off the stirring paddle of a bucket of paint that's already at your desired thickness. When the paint flow is similar in your thinned bucket, it's time to stop adding water.

Filtering Out Lumps

• Some paints become lumpy or ropy when they have been kept in storage too long. Pro painters will often thin their paint to the desired consistency by pouring the paint into a different bucket while filtering it through an inexpensive disposable strainer bag. The bags are available in one- and five-gallon sizes with an elastic top that wraps around the top of the bucket.

Thinning by the Brush Load

• Instead of thinning the entire bucket of latex paint, some painters prefer to thin it as needed, one brush stroke at a time. To keep the paint from becoming too thick on the wall, simply keep a container of water next to the paint bucket and dip the brush in the water occasionally before dipping it into the paint. Once you've developed a feel for the proper viscosity, you can apply the paint without causing any irregularity in your semi-gloss sheen.

Add Paint Conditioner

• The safest and most accurate method for thinning an interior latex paint is by adding a flow conditioner such as Floetrol to the bucket. The conditioner improves the flow of paint off the brush or roller and helps the paint to dry without brush marks. Properly used, a latex flow conditioner will ensure that your semi-gloss paint dries to a uniform semi-gloss finish.