I recently was asked about the optimum viscosity for spraying paint. I thought that I would extend my answer to other application methods and share the information. There is a rule of thumb in the paint industry that a viscosity of approximately 100 cps (1 P, 0.1 Pa•s) provides acceptable spraying, brushing, or roll coating.. A. Hi again Manikantan. Method ASTM D1200 covers viscosity measurement with the Ford Cup. Please also try to also get hold of the ASTM Gardner/Sward Paint Testing Manual [on Amazon affil links] as it has an excellent chapter on the subject of viscosity and its measurement with the various cups and devices. It includes a chart by Euverard showing a conversion factor of 3.7 for the Ford #4 cup.
Once you have measured the viscosity of your paint sample, you can use a viscosity chart or formula to determine the viscosity in centipoise (cP). You can also compare your results to a viscosity standard to ensure accuracy. If your paint viscosity is too high, you may need to add more solvents or thinners to achieve the desired consistency.. These instructions pertain to the Zahn viscosity cup. Viscosity refers to the thickness or internal friction of a coating. This measurement determines which size turbine and atomizing set (needle, nozzle and air cap) to use with your HVLP paint spray gun. The easiest and most affordable way to measure viscosity is with a Zahn Viscosimeter.