It is the only pyrogallol tannin which does not deposit bloom, or ellagic acid, on the leather.
Another of these substances is ellagic acid C14H6O8, a double lactone of a hexa-hydroxy-diphenyldicarboxylic acid.
This operation has for its object the removal of bloom (ellagic acid) and any other superfluous adherent matter.
It deposits much bloom (ellagic acid) and is largely used for brightening the dark colour produced by other tannins.
It is known technically as bloom and chemically as ellagic acid.
ellagic acid el·lag·ic acid (ĭ-lāj'ĭk)
A yellow crystalline compound that is obtained from tannins and used as a hemostatic.