Paint viscosity is extremely important when you are spray painting. Failure to have the right viscosity of the paint will lead to the paint either being too thin or too thick. When the paint is too thin you will leave marks and streaking on the painted surface. When the paint is too thick it will clog the spray gun, leaving a rough finish. Fortunately, with the right supplies and directions you can quickly and accurately calculate the right viscosity for the paint.
Read the packaging of the paint you wish to thin. Read the instructions to see if the paint can be thinned with water or a specific solvent. All latex based paints can be thinned with water, most oil based paints can be thinned with paint thinner. Some speciality paints require special solvents to thin the paint.
Pour all the paint you want to thin into the paint bucket. It is important that all the paint cans are mixed together in the bucket to ensure a uniform colour. Keep a small amount of extra paint on hand, so you can add it later on if the paint becomes over thinned.
Thin the paint by adding 20 percent of the amount of paint poured into the bucket with the proper solvent.
Mix the paint vigorously with the paint mixing stick until the solvent has been completely mixed into the paint.
Add a small amount of the mixed paint into the spray gun and apply it. If you notice that the colour is transparent then you must add at least five percent more paint into the paint bucket and remix it. If you notice the paint is still thick add five percent more solvent to the paint bucket and retest it. Keep adding more solvent or paint until the paint flows easily out the spray gun and covers the surface with the colour.