27 CFR 24.216: Distilling material.

Wine may be produced on bonded wine premises from grapes and other fruit, natural fruit products, or fruit residues, for use as distilling material, using any quantity of water desired to facilitate fermentation or distillation. No sugar may be added in the production of distilling material. Distillates containing aldehydes may be used in the fermentation of wine to be used as distilling material. Lees, filter wash, and other wine residues may also be accumulated on bonded wine premises for use as distilling material.