Having not done any modelling like this for a very long time, I've just been coating the wings of a small model aircraft with a 1:1 dope / cellulose thinners mix and as it has dried, rather than going clear, it has produced a white deposit / residue (smooth, but quite hard, not readily amenable to sanding off on a wood surface - I haven't tried to remove it from the tissue covering!). Apart from the fact that it is unattractive cosmetically, it seems to be doing the job just fine. Has anyone else seen this? Any ideas why / how to prevent it? It is definitely the dope and / or thinners that has produced it and not the paper / wood surfaces it is applied to as samples dry out the same on any surface I've tested it on.
Many thanks in advance for any suggestions.