Ready to try 3608S here. Used sig thinner on my all sig dope finish on the new plane, and it acted awfully hot. Thinned 50/50, the final clear when shot caused the polar grey blocking coat to bleed through the white, making the plane look moldy in places. Also had blistering pop up where I went extra heavy with the clear, like over trim colours and lettering. The one good thing with the all sig is that the finish is mechanically bulletproof-I could probably mask with duct tape and not have any lifts or pulls.
Alternately, I may do the finish with Sig up to final clear, then shoot DuPont 480S clear to finish it off.
Hi Steve,
Of the butyrate thinners I use I have observed the following characteristics:
1. Sig thinner is the slowest drying of the three that I use.
2. Randolph is the next slowest drying butyrate thinner.
3. Certified brand is the fastest drying of the three, and is still quite a bit slower drying than lacquer thinner.
Because Sig is a relatively slow drying thinner I can spray on a little less material and it will still flow out to a glossy finish. I like Sig thinner a lot. Randolph is also an excellent medium drying thinner for all butyrate dopes. Certified butyrate thinner works well also, and is the fastest drying of the three.
Although many builders use lacquer thinner to thin butyrate dopes I do not. You can get away with using it because our models are a relatively small area to paint compared to a full-scale airplane, so the faster drying rate of the lacquer thinner doesn't matter as much. The cost of lacquer thinner has gotten right up there with the cost of Randolph or Certified thinners.
I think that the problem of the Sig thinner being "hot" & the bleed-through of the polar gray is caused by shooting too heavy a coat of the Sig material. I use Sig dopes & thinners regularly & don't have the problem of bleed-through. The best way to use butyrate dope is to thin it 50% as you mentioned and apply more coats rather than heavy ones.
You will find that DuPont 480s clear lacquer is one of the least fuel-resistant finishes you can use. It has a beautiful gloss as sprayed and is easy to polish to a fantastic gloss, but you have to be very careful to keep raw fuel & exhaust residue off of it. Tuned pipe engines, if you are careful while fueling them, work well with clear lacquer due to the minimal exhaust residue that gets on the airplane.