(a) A special industrial solvent is any article made with any other ingredients combined with the ingredients in the minimum ratios prescribed in this section. A special industrial solvent shall be made with S.D.A. Formula No. 1, 3A, or 3C containing, for every 100 parts (by volume) of S.D.A.:

(1) No less than 1 part (by volume) of one or any combination of the following: methyl isobutyl ketone, methyl n-butyl ketone, nitropropane (mixed isomers), propylene glycol monomethyl ether, or ethylene glycol monoethyl ether, and

(2) No less than 5 parts (by volume) of one or any combination of the following: ethyl acetate (equivalent to 85% ester content, as defined in §21.107 of this chapter), isopropyl alcohol, or methyl alcohol.

(b) Special industrial solvents are intended for use as ingredients or solvents in manufacturing processes and shall not be distributed through retail channels for sale as consumer commodities for personal or household use. When a special industrial solvent is used in the manufacture of an article for sale, sufficient ingredients shall be added to definitely change the composition and character of the special industrial solvent. A special industrial solvent shall not be reprocessed into another solvent intended for sale if the other solvent would contain more than 50% alcohol by volume.

[T.D. ATF-199, 50 FR 9162, Mar. 6, 1985, as amended by T.D. TTB-140, 81 FR 59457, Aug. 30, 2016]