In the north, meat may be kept fresh during the cold season by freezing it solid. The carcass may be cut into quarters or smaller pieces and hung in an open outbuilding where it will freeze solid, and remain frozen until the weather begins to warm up in the spring. Whenever a piece is wanted it can be removed with a saw. Rapid thawing of frozen meat greatly injures its flavor. If the meat is thawed out slowly in a cold room, the flavor of the meat will not be injured. Meat can be kept frozen for months if kept in cold room, or in a refrigerator with a temperature below 32 degrees Fahrenheit and with proper ventilation provided. Curing Meats: American Methods § 34. Preparing the Meat for Curing Meat should be thoroughly cooled before it is cured, or it will spoil. The proper time to begin curing is when the meat is cooled and still fresh. Twenty to thirty hours after killing is the proper time to begin the cure. If salted before the animal heat has left it, the shrinkage of muscles causes a retention of gases, and gives an offensive odor to the meat. The meat should not be frozen, as the cure will not penetrate such meat evenly, and an uneven curing will result. Tainted meat may be cured so that it will keep, but no system of curing will bring back the natural flavor of the meat, if it is once lost. § 35. Vessels for Curing Vitrified clay jars, with straight sides, similar to the jars used for fermenting beans in making soy bean sauce, are the best vessels for containing the meat. These jars, large enough to hold conveniently the hams, shoulders, and sides of two hogs, are best for curing meat for the first time, and the meat can be watched and cared for better in small jars than in large jars containing more meat. In America, where such jars are expensive, it is the custom to use a clean, hardwood barrel for the purpose. One that has been used for syrup or molasses is best. If a kerosene or tar barrel is used, it should be first thoroughly burned out, and used as a water barrel for some time before it is used for meat. Vitrified clay jars are preferred to wooden barrels as they are cleaned more readily. If meat has once spoiled in a wooden barrel, the vessel should not be used again for containing meat. Vessels that are used repeatedly for curing meat should be scalded thoroughly each time before packing with fresh meat. § 36. Curing Agents Salt, saltpeter, sugar or molasses, and a variety of spices are the principal preservatives used in curing meat. Borax, formalin, salicylic acid, and other chemicals are sometimes used. However, as they are considered by many authorities to be injurious to the health, their use should be avoided. Baking soda is used in wet pickles to check the growth of mould.