RE: Plasticized dope mixture
About 6 drops of Castor Oil to a cup of thinned (50%) dope to plasticise over silk or silkspan. The talc should only be used over solid wood or silk covered wood to fill the grain. You then sand most of it off untill you can see but not feel the grain or weave. I would not use dope and talc over silk or silkspan.
Regards