Black spirit varnish and other names refer to black shellac.  Unless
you have several broken 78 rpm records I wouldn't break up any of those.

I make it by dissolving alcohol-soluble black aniline dye into some
methanol and then dissolve shellac flakes into that.  This is also
known in England as "button polish" as it was used to French polish
buttons at one time.

Doug L Bullock