More Waterborne Coatings In Summer

Q. I have some thoughts on the question asked by L. M. in the October Painting Clinic with regard to the sagging of waterborne coatings in the Summer months. As you point out, when we wanted solvent-borne coatings to set up quickly, we could adjust the solvent-balance and/or preheat the parts to drive off the solvents.

Unfortunately this does not always work with waterborne materials. L. M. states that the parts are “warm” after heating to 650°F, so I would assume that they have mass to them. By preheating the parts, L. M. may be making the problem worse since the warmth of the part might be lowering the viscosity of the coating and contributing to the sagging problem. The water will not, and some of the co-solvents may not, evaporate from a “warm” product. You did point this out in your reply to him.
I would suggest that L. M. try not heating the product. If he is preheating the product to drive off any cleaning fluids, that just complicates the situation. If this should be the case, the parts should cool before coating application. He should also contact his paint supplier to see if the co-solvent balance can be adjusted.

While it’s true that the humidity in the summer is higher, it is also true that putting in a controlled air makeup setup can be expensive. He should do the easy stuff first. S. B.

 

A. Thanks for pointing out the alternative approaches, S. B. It’s always comforting to have someone looking over your shoulder.