FYI...this is how I make the pitch varnish I use to seal sinew wraps. This is not a true varnish because it doesn't have any oil in it but it works just fine for what I use it for.
First you start with hard, brittle pitch. If you use softer pitch the varnish will remain sticky and not harden. I place the pitch nodules in a clean, air tight jar and cover it with denatured alcohol. Any alcohol will work even Ever Clear or moonshine. Other solvents will also work but denatured alcohol is the least dangerous to use.
The jar in the pic has had the ingredient in it for about an hour. It usually takes over night for all the pitch to dissolve into the solution. After this you can strain out the impurities which usually sink to the bottom. If any floats I remove it but don't worry about what's on the bottom.
To apply I use a small artist paint brush, dip it in the varnish and apply it to the sinew wrap. As soon as the alcohol evaporates the varnish is hard. Don't worry about cleaning the brush. The next time you use it it will soften when it goes in the varnish.