Inconsistent Gloss Readings

Q. I run a custom coating shop. One of my customers has me painting parts using a MIL Spec two-component paint which we buy from a QPL source. My customer requires a 60-degree gloss reading between 15 and 30. I cannot get satisfactory results from day to day. Some days the gloss is too high, some days it is too low. The paint is from the same kit but reacts differently from day to day. Where do you suggest I look for answers to my problem? T. R.

 

A. I suggest you look no farther than your painting operation. Admittedly, it is difficult to control gloss of coatings in the lower ranges. However, careful attention to procedures will produce good results. The same paint sprayed wetter or dryer will give different gloss results. You must control important parameters including spray gun to part distance, gun travel speed, paint viscosity, paint temperature and spray gun inclination to mention a few. It is important to note that, since your coating material is multi-component, pot life, paint temperature and viscosity are interrelated. As the reaction of the mixed components progress, the paint temperature increases and the viscosity decreases. Once you have established the parameters, it is wise to have the same painter paint these parts.