Put gum shellac into a glass or earthen vessel (a wooden box coated
inside with glue makes a very good vessel in which to dissolve
shellac), and pour over it alcohol enough to cover the shellac; keep
stirring it until no lumps remain. This will take from two to three
hours, according to quantity. If left in a tin can the shellac becomes
very dark. To clear it when dark add a little oxalic acid and stir
until cleared.