Here's a little item that may be a heads up for others about to head into the paint booth to put the finishing touches to that new airframe.
As mentioned here over the last couple of months, I've been trying to get a Sig Magnum finished, at long last. Well, it's getting closer still to first flight, (yeah I'm tried of saying it, your tried of hearing it right?). So to the tip:
I'm at the point of putting on some base clear coats of Brodak dope. With the hot humid summer we've had up until late I've been adjusting the dope mix to help control blush. Changing thinner to dope ratios, and adding retarder as needed, etc..
Well yesterday afternoon while trying to get some clear on the bird, I got nothing but blush on my test shot piece 
(taking a page from Windy's finishing book re; the test shot) . No matter what I did with the dope mix I still got blush:-(. So the equipment was shelved, and the gray matter was put to work.
Hmmm, what the heck could it be? About three hours later I took the project inside , and did the short test shots again in a aircon/dry atmosphere, ..STILL GOT BLUSH !!!!!! (Light bulb goes on)
The moisture is not in the atmosphere, it's in the air I'm using, ..DUH!!
I've been draining the compressor low point as part of the process all a long, but had forgotten about the built-in moisture trap in the pressure regulator, and the inline filter. With the system under pressure I blew-down these two items, and got lots of water at the petcocks, ..go figure.
So now the new procedure will be to give the air supply system a blowdown at regular intervals during the job , or when every the mood strikes. Anyway I will not be forgetting this one anytime soon. Of course the rest of you have already been doing this right?
Tony