After the active stages of a fermentation have passed, store the food in a cool place. Low temperatures are always an aid in the preservation of food products. COLORING AND HARDENING AGENTS To make what is thought to be a better looking product, it is the practice in some households to "green" pickles by heating them with vinegar in a copper vessel. Experiments have shown that in this treatment copper acetate is formed, and that the pickles take up very appreciable quantities of it. _Copper acetate is poisonous._ By a ruling of the Secretary of Agriculture, made July 12, 1912, foods greened with copper salts, all of which are poisonous, will be regarded as adulterated. Alum is often used for the purpose presumably of making pickles firm. The use of alum in connection with food products is of doubtful expediency, to say the least. If the right methods are followed in pickling, the salt and acids in the brine will give the desired firmness. The use of alum, or any other hardening agent, is unnecessary. TABLES AND TESTS Table 1.--_Salt percentages, corresponding salinometer readings, and quantity of salt required to make 6 quarts of brine_ -----------+------------+-------------- | | Salt in Salt in |Salinometer | 6 quarts of solution | reading |finished brine -----------+------------+-------------- _Per cent_| _Degrees_ | _Ounces_ 1.06 | 4 | 2 2.12 | 8 | 4¼ 3.18 | 12 | 6½ 4.24 | 16 | 8½ 5.3 | 20 | 11 7.42 | 28 | 14½ 8.48 | 32 | 18 9.54 | 36 | 20 10.6 | 40 | 22½ 15.9 | 60 | 35 21.2 | 80 | 48 26.5 | 100 | 64 -----------+------------+-------------- The figures given in the first two columns of Table 1 are correct. Those in the last column are correct within the possibilities of ordinary household methods. To make up a brine from this table, the required quantity of salt is dissolved in a smaller volume of water and water is added to make up as nearly as possible to the required 6 quarts. One pound of salt dissolved in 9 pints of water makes a solution with a salinometer reading of 40°, or approximately a 10 per cent brine. In a brine of this strength, fermentation proceeds somewhat slowly. Pickles kept in a brine maintained at this strength will not spoil. One-half pound of salt dissolved in 9 pints of water makes approximately a 5 per cent brine, with a salinometer reading of 20°. A brine of this strength permits a rapid fermentation, but vegetables kept in such a brine will spoil within a few weeks if air is not excluded. A brine in which a fresh egg just floats is approximately a 10 per cent solution. Fermentation takes place fairly well in brines of 40° strength, and will, to some extent at least, up to 60°. At 80° all fermentation stops.