For the production of the best butter, it is necessary that the cream should be sufficiently sour before it is put into the churn. Butter made from sweet cream (not clouted) is neither good in quality, nor large in quantity, and longer time is required in churning. It is an unprofitable method. [Illustration: Fig. 18.] Fig. 18 is a _Cylindrical Thermometer Churn_, of any required size, with false metal bottom to hold cold or hot water for bringing the cream to the proper temperature. A thermometer, permanently set in the side, indicates the heat. Quickness in Churning. The more quickly milk or cream is churned, the paler, the softer, and the less rich the butter. Cream, according to Mr. Aiton, may be safely churned in an hour and a half, while milk ought to obtain from two to three hours. The churning ought always to be regular, slower in warm weather, that the butter may not be soft and white, and quicker in winter, that the proper temperature may be kept up. A barrel-churn, lately introduced into this country, being placed in a trough of water of the proper temperature, readily imparts the degree of heat required by the milk or cream without the necessity of adding warm water to the milk, _and churns the whole in ten or twelve minutes_. It is said also to give a larger weight of butter from the same quantity of milk. If the quality be really as good by this quick churning, the alleged inferiority in the quality of butter churned quickly in the common churn cannot be due to the mere rapidity of churning alone. Over-churning. When the process of churning is continued after the full separation of the butter, it loses its fine yellowish, waxy appearance, and becomes soft and light-colored. The weight of the butter, however, is considerably increased; and hence, in Lancashire, over-churning is frequently practised in the manufacture of fresh butter for immediate sale. Temperature of the Milk or Cream. Much also depends upon the temperature of the milk or cream when the churning is commenced. Cream when put into the churn should never be warmer than 55° Fahrenheit It rises during the churning from 4° to 10° F. above its original temperature. When the whole milk is churned, the temperature should be raised to 65° F., which is best done by pouring in hot water into the churn _while the milk is kept in motion_. In winter, either of these temperatures may be easily attained. In cold weather it is often necessary to add hot water to the cream to raise it even to 55°. But in summer, and especially in hot weather, it is difficult, even in cool and well-ordered dairies, (without the use of ice,) to keep the cream down to this comparatively low temperature. Hence, if the cream be then churned, a second-rate butter, at best, is all that can be obtained. The alleged advantages of Churning the entire Milk.