A proprietor must obtain approval of a formula on form TTB F 5100.51 as provided in §§5.26 and 5.27 of this chapter before a proprietor may:

(a) Blend, mix, purify, refine, compound, or treat spirits in any manner which results in a change of character, composition, class, or type of the spirits, including redistillation as provided in §19.314; or

(b) Produce gin or vodka by other than original and continuous distillation.

(26 U.S.C. 5201, 5555)