thinning randolph dope for use
05-15-2004, 09:12 AM
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thinning randolph dope for use
i'm planning to use full-scale randolph clear non-tautening butyrate dope for 40 and 60 size planes, on top of 5 momme thai silk (habotai). Guys have told me they dilute the full strength with thinner to get down to the consistency of brodak/sig etc. Any idea how much dilution--50%?, or should i use straight. I always 50% diluted sig with great results--please advise. What recipe do you use for retarder? How do you dilute the colored dope? For weave filling, how much talc are you adding to the diluted (or straight) randolphs dope? Has anyone used certified brand dope?
05-15-2004, 01:46 PM
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RE: thinning randolph dope for use
Havn't used it for a long time, but mixed it half and half most of the time depending on the viscosity of the dope. After the dope was mixed then mixed the talc and dope half and half. Talc thickens the dope quite a bit but thats the idea for filling. Sands very well. Hope this helps. A place to start anyway.
05-17-2004, 10:22 AM
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RE: thinning randolph dope for use
The classic formula for dope and talc is equal amounts of dope, thinner, and talc. I don't know anyone who puts the talc over open silk covering, though. Awful to sand and can get heavy fast.
Your first coats may need to be thinned as much as 60-70%, then go to 50% for the later coats. Be prepared to apply lots of coats for a nice finish. Dope is very low in solids, so it fills the cloth weave pretty slowly. Your colors will likely need to be thinned 50-60% for spraying, too.
Only use retarder if you get blushing from painting in high humidity. The rule of thumb is as little as possible and then not more than 15%. If you need that much, it's better to wait for a dryer day. Too much retarder can burn into the coats underneath and make a mess.
Randolph and Certified are both fine products. Randolph makes the model dope for Brodak, and it is really pretty and easy to work with.
FWIW, you'll sometimes here of someone having compatibility problems because of using other than the maker's thinner. Now always, just on occasion. So the safest route may be to stick with same brand products all the way through a project. The lacquer thinner and such usually work, but once in a while...The thinner used can effect the drying and adhesion of the dope.
Your first coats may need to be thinned as much as 60-70%, then go to 50% for the later coats. Be prepared to apply lots of coats for a nice finish. Dope is very low in solids, so it fills the cloth weave pretty slowly. Your colors will likely need to be thinned 50-60% for spraying, too.
Only use retarder if you get blushing from painting in high humidity. The rule of thumb is as little as possible and then not more than 15%. If you need that much, it's better to wait for a dryer day. Too much retarder can burn into the coats underneath and make a mess.
Randolph and Certified are both fine products. Randolph makes the model dope for Brodak, and it is really pretty and easy to work with.
FWIW, you'll sometimes here of someone having compatibility problems because of using other than the maker's thinner. Now always, just on occasion. So the safest route may be to stick with same brand products all the way through a project. The lacquer thinner and such usually work, but once in a while...The thinner used can effect the drying and adhesion of the dope.
