Yes, the damar gum is mentionned in the book of B.Lavédrine. In this book you can read that this gum is dissolved in "acétate d'éthyle"...i don't know the good word in english. .
I have the answer of an enterprise which sell varnish and they said to me that all the cellulose varnish are not transparent....they say to take a polyuréthane/acrylique varnish. Now i have to know how is made this varnish...imagine that it dissolve the first varnish .