[Code of Federal Regulations]
[Title 27, Volume 1]
[Revised as of April 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 27CFR30.31]

[Page 811-812]
 
            TITLE 27--ALCOHOL, TOBACCO PRODUCTS AND FIREARMS
 
 CHAPTER I--ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE 
                                TREASURY
 
PART 30_GAUGING MANUAL--Table of Contents
 
                      Subpart D_Gauging Procedures
 
Sec. 30.31  Determination of proof.


    (a) General. The proof of spirits shall be determined to the nearest 
tenth degree which shall be the proof used in determining the proof 
gallons.
    (b) Solids content not more than 600 milligrams. Except as otherwise 
authorized by the appropriate ATF officer, the proof of spirits 
containing not more than 600 milligrams of solids per 100 milliliters of 
spirits shall be determined by the use of a hydrometer and thermometer 
in accordance with the provisions of Sec. 30.23 except that if such 
spirits contain solids in excess of 400 milligrams but not in excess of 
600 milligrams per 100 milliliters at gauge proof, there shall be added 
to the proof so determined the obscuration determined as prescribed in 
Sec. 30.32.
    (c) Solids content over 600 milligrams. If such spirits contain 
solids in excess of 600 milligrams per 100 milliliters at gauge proof, 
the proof shall be determined on the basis of true proof determined as 
follows:
    (1) By the use of a hydrometer and a thermometer after the spirits 
have been distilled in a small laboratory

[[Page 812]]

still and restored to the original volume and temperature by the 
addition of pure water to the distillate; or
    (2) By a recognized laboratory method which is equal or superior in 
accuracy to the distillation method.
    (d) Initial proof. Except when the proof of spirits is used in 
making the guage prescribed in 27 CFR 19.383 or in making a gauge for 
determination of tax, the initial determination of proof made on the 
bonded premises of a distilled spirits plant for such spirits may be 
used whenever a subsequent gauge is required to be made at that same 
plant provided that no material has been added to change the proof of 
the spirits.

(Sec. 201, Pub. L. 85-859, 72 Stat. 1358, as amended, 1362, as amended 
(26 U.S.C. 5204, 5211))

[T.D. ATF-198, 50 FR 8535, Mar. 1, 1985]