I'm hoping that Technetters can share some light on an issue that we occasionally experience here - we coat some of our boards with 1B73 conformal coating, for some we have a spary machine, others a sprayed by hand. 

Every so often we will process some board through coating and they will have a cloudy / milky appearance in the coating. We have been told previously that this happens when humidity is up, since our manual spray coating area is not in an air-conditioned environment. 

Anyone else ever have this problem? How did you fix it? 

Thanks,

Blair