Some paints are too thick to apply evenly if you’re using a spray gun. Because a spray gun forces paint through a tiny tip in order to achieve an even pattern of spray, the paint must be thin enough to easily exit the spray gun. However, if the paint is too thin, it will result in poor coverage, and it may also run and streak. Knowing how to thin the paint correctly is imperative to a successful project.
Be safe. Some paints, especially oil-based paints, emit toxic fumes that may be inhaled when spraying. Wear a respirator and put on a pair of safety goggles for eye protection.
Read the paint label to determine the correct fluid with which to thin the paint. Latex paints are thinned with water but oil based paints require mineral spirits, a commercial paint thinner or another solution which will appear on the paint can’s instructions. Some paints are marketed as non-thinable, so look on the label before purchasing.
Strain the paint. Professional painters can confirm that even in paint cans that are treated with a high-powered shaker, small clumps of thickened material commonly occur. Any of these thicker clumps will clog a paint sprayer. Use a regular paint strainer, place it over a clean bucket and pour the paint through.
Fill the spray gun reservoir and run a small amount of paint through, using a test board to determine the thickness of the paint. If the paint comes out easily in a fine mist and covers the board without running, go ahead and begin painting your project. If the spray gun sputters or the pattern of spray is clumpy and inconsistent, thin the paint before testing again.
Add only a small amount of thinner at a time but add it to the entire bucket of paint. To keep from having to stop and thin small amounts, it’s easier to thin all of the paint at one time. For latex paint, add ¼-cup of water per 1-gallon of paint and stir until smooth.
Stir mineral spirits or other paint thinner into oil based paints at the rate recommended on the paint can or at the same ratio used for latex paint thinning.
Test the paint after each addition of thinner. When spray comes out smoothly it’s time to paint your project.