As an antique dealer and restorer and collector shellac and I go way back. One tip not often given is this. Buy it in the smallest amounts available, use it and throw it away. Buy new for the next project...it is very inexpensive. Shellac is anhydrous and will draw moisture from the air. If this happens to your stash of it your next application of it will have a white, cloudy 'bloom'. This usually means stripping it off with alcohol and starting over. Pure frustration!
Tom Sanders
Lansing, Mi