blush city

This is Houston in the summertime... I put a coat of Sig butyrate dope over Sig nitrate dope and it blushed like crazy.
Is there anything I can do the fix it? How can I keep it from happening in the future?

Try adding some retarder, but I wouldn't exceed 15 % or you could soften things like your canopy !!! The idea is to slow down the drying time to let trapped moisture out.. I have been using P P G acrilic (sp?) lacquer retarder from my local auto paint and body supplier..
Hope that this helps...

Gil

Ron:

Since I live here I share your pain and with you in clear lake only a few miles from the water you will have more of a problem. The solution obviously is a closed area with air-conditioning or a couple de-humidifiers. Lacking that use the retarder Gil mentioned and get the SLOWEST lacquer thinner you can find. The rating is usually given in temperature get the highest you can find 95-110 deg. The humidity varies greatly during the day with the afternoon having the lowest level @70% or so, anything before 10AM unless you are in airconditioning forget it.

If the blushing is in the color coat spraying the clear coat with retarder and slow thinner will usually clear it up, same for the clear coat. The two part auto paints and clear coat don't seem to have this problem, again use the slowest reducer you can find.

This year has been unusually wet especially June, we normally have a week or two where there is no rain and the humidity actually gets below 50%, however this year we are over 20 inches ahead in our rainfall.

We normally have @ 2-3 good days in late October early November and @ 2-3 more in late February early March when you can paint with no problem.

Yea, same here. The humidity has been very high (70-90 range). I'm going to be painting clearcoats on my classic plane in a week or so. If it doesn't settle down, I'll wait.

This is the shortened version of a long story... I wanted to try a dyed clear on silkspan to get a light weight finish for a beginner's (me) plane that would look better than just plain clear on silkspan. I've used the plastic coverings and just don't get the knack of doing a good job with them. Even after a lot of "fiddlin'" I still have some ugly places and then it gets worse when they get in the sun and get warm. Anyway... after reading much on this forum about finishes I got some Sig nitrate dope and dyed it with casting resin dye. That much worked well. My choice of colors (yellow) was probably a poor choice. It would have worked better in blue or red. This style of finishing shows up every flaw in the joinery (and I've got lots of those). It also did some things I didn't expect: The nitrate didn't shrink the silkspan as much as I expected. I learned (later) that Sig nitrate is the non-tautening varity and should be used where you don't want shrinkage. The Silkspan is "OK", just not as taut as I'd like. So, then I thought I'd shrink it a bit with a couple of coats of Sig butyrate. And this is when it blused. Big time. I had planned to use the butyrate as a fuel proof clear coat over the complete plane after all the color was done... On the joinery suprise side of things: the ends of the cap strips swelled and bulged up slightly. I had carefully sanded everything flat/smooth before covering but when I put on the silkspan the cap strip joints at the trailing edge and the leading edge sheeting bulged. The wet silkspan maybe? It didn't go away when the silkspan dried and I'd precoated everything with several coats of nitrate. This is my first wing with cap strips (cap strips are a pain...). End grain: I discovered that exposed endgrain swells more than the surounding flat grain resulting in an ugly "ridge".

I could wirte a book on things done wrong...

One thing that did work well was using PC to put light weight silkspan on the balsa sides and tail. I really does make it easier to fill the balsa grain. It does need to dry completely befor it is sandable and that takes at least 24 hours in the Houston environment and it continues to dry (cure?) for quite a while after that.

Oh well. live and learn. The next one will be better (I hope...)