Damar, copal, and making varnish
I know there are several artists on this board, and a lot of collected knowledge, so maybe somebody has some advise.
I'm trying to make my own varnish - for coating guitars, not paintings. However, the requirements, and thus the formulas, are similar.
Currently I am using seedlac dissolved in alcohol applied in a french polish manner, using walnut oil as a hardener. A Tried and True technique. However, I hear a lot of murmering about additives added to the shellac to improve it's hardness. Copal and Sanderac are the two most mentioned. However, if people really are using this, they are keeping pretty tight lipped.
The point of the additive is to add hardness to the shellac, without affecting it's positive qualities of being quite flexible (wood expands and contracts, so flexibility is important). Additives that are dissolvable in alcholol are preferred, to keep the entire solution alcohol based, but I am willing to investigate
If anyone has any knowledge of making their own varnish, or better yet, can point me to a definitive resource that discusses different mediums used in the art world, it would be extremely helpful to me. I realize that this is not a question that can be answered with a simple "take x of Y, add it to..." but a lead on where to gather knowledge to start my own experiments would be invaluable to me.