The particular brand and model of paint sprayer you use will come with detailed instructions for thin the paint--if any thinning is required. It will also come with detailed instructions on required air pressure as well as spray tips needed for different kinds of paint. Paint guns from different manufacturers (and, indeed, different models from the same manufacturer) have different requirements. To complicate matters slightly, oil-based paints require a different type of thinning than do latex paints. Airless paint guns, which can be rented at most paint rental stores, do not require any thinning of paint.
Instructions
1. Set air pressure to the manufacturer's specifications for the particular air gun. Make sure you have the proper spray tip for the type of paint being used.
2. Strain paint through a paint strainer to remove lumps or any impurities that could clog the tip of the sprayer. This is a time-consuming but important step.
3. Thin latex house paint with Flotrol. Follow the paint gun manufacturer's instructions for thinning paint. If unsure, use Flotrol sparingly--more can be added later if additional thinning is required. Unless specified otherwise, do not thin paint by more than 15 to 20 percent.
4. Thin oil-based house paints with Pentetrol. Again, follow paint sprayer's instructions regarding thinning, but do not thin by more than 15 to 20 percent.
5. Spray a swath of paint onto a piece of cardboard or scrap lumber. Keep the sprayer moving in a smooth motion. If the paint comes out in globs, then additional thinning is required. If a line appears at the top and/or bottom of the swath, you have thinned too much--mix in a small quantity of un-thinned paint.
6. Continue painting sample swaths on cardboard or scrap lumber until the paint flows from the sprayer evenly. When painting, keep the sprayer moving constantly and do not worry about putting on too light of a coat. Additional light coats can be sprayed later.
