Good article on Dope. How and why we do it. https://www.aircraftspruce.com/catalog/kitspages/copingvsrebuilding.php Part 2 is here. https://www.aircraftspruce.com/catalog/kitspages/perspectivesMarch2015.php And last but not least: https://www.aircraftspruce.com/catalog/kitspages/perspectivesMay2015.php?clickkey=83004

Exactly Ty! 😁. But seriously it was more like, how much faster the ultra violate light destroy our silkspan covered models without the silver blocking coat?

I didn't read every work of every article but this part glared at me. 

"Nitrate dope must be used on polyester fabric as the initial coat. Butyrate dope will not adhere to polyester fabric, only nitrate. Therefore, the first few coats of chemicals must be nitrate dope. Butyrate dope is then used to build up over the nitrate dopes that are in place."

Polyspan is polyester and yes you can butyrate from bare wood up though finish but the truth is that nitrate does in fact work better for sticking the stuff down.  I honestly can't understand why people have problems with butyrate over nitrate.  It works, every time.  The Polyspan sticks better and the weave fills faster.  AND Nitrate is less expensive, notice I didn't say "cheaper" because non of it is cheap. 

We are fortunate to have a local supplier of Randolph products.  I bought a gallon of nitrate non-tautening quite a few years ago and am still working on it.  I use their butyrate thinner in it and also cheap thinner from Lowes.  The only problem I've had with cheap thinner is blushing, and only then if applied to heavily.  Light coats in warm, not humid air helps a lot.