§ 1220.64 - Tests for impurities.

(a) To examine for impurities the following tests may be used in comparison with the standard:

(1) Read test, with additions and modifications, and the cup test, doubleweight. Place 2 ounces of tea in a sieve 5 or 6 inches in diameter, having 60 meshes to the inch and provided with a top. Sift a small quantity of the dust onto a semiglazed white paper about 8 by 10 inches. The amount of dust placed on the paper should be approximately 1 grain. To get the requisite amount of dust it is sometimes necessary to rub the leaf gently against the bottom of the sieve, but this must not be done until the sieve has been well shaken over the test paper. Pour the dust thus collected from the paper into the scales, weigh out 1 grain, and return this quantity to the same paper, distributing it well over the surface of the paper. Then place the paper on a plain, firm surface, preferably glass or marble, and crush the dust by pushing over it, with considerable pressure, a flat steel spatula about 5 inches long. Do this repeatedly until the tea dust is ground almost to a powder and the particles of coloring matter or other impurities, if any, are spread or streaked on the paper, so as to become more apparent. Brush off the loose dust and examine the paper by means of a simple lens magnifying 71/2 diameters. In distinguishing these particles and streaks bright light is essential.

(2) The crushed leaf in either black or green tea appears in such quantity that there is no chance of mistaking the leaf for artificial coloring, facing material, or other impurities.

(3) The test is performed in comparison with the standard, and, if the tea is clearly equal to the standard with respect to artificial coloring, facing matter, or other impurities, the operation need not be repeated. If particles of artificial coloring, facing, or other impurities are found in the sample under comparison with the standard repeat this operation a sufficient number of times to be sure whether or not the tea contains impurities in excess of the standard.

(4) Repeat the operation, using -semiglazed black paper instead of the white paper. This black-paper test shows the presence of facing and other impurities, such as talc, gypsum, barium sulfate, clay, and kaolin.

(5) If the tea under examination is found, by the foregoing tests, to contain more impurities than the standard, draw samples from packages representing at least 5 percent of the line in question, and subject each sample to the tests to ascertain whether or not the majority contain impurities in excess of the standard.

(6) The foregoing tests may be applied to tea of all varieties.

(b) Should the examination of the sample by the cup test, double-weight, for scum, sediment, etc., or the Read test, or both, disclose the presence of more impurities than the standard, a pound sample should be sent to the nearest district of the Food and Drug Administration and an analysis made in comparison with the standard to determine whether it contains more impurities than the standard. If the tea in question is found to contain more impurities than the standard, it would properly be rejected as not being equal to the standard in purity.

(c) All extraneous substances are impurities, and the presence of any may be detected in any way found efficient.