SOME COMMON MACHINES 529 



THE CREAM SEPARATOR 



620. Importance of the Cream Separator. The cream sep- 

 arator is found nowadays in almost every creamery, in every 

 city milk-supply house, in many dairies, and on most farms 

 where any considerable quantity of milk is produced. It is 

 one of the most common and useful machines. As its name 

 implies, it is a machine used to separate the cream from the 

 other portions of whole milk. 



621. Former Methods of Separating Cream. Primitive 

 man doubtless separated cream from the other portions of 

 milk from the time he first began to use as food the milk from 

 his herds of goats. Until recent times the separation was 

 usually made by placing the milk in shallow crocks, jars, or 

 pans. The cream, being lighter than the other portions of 

 the milk, rose to the top and could then be removed, leaving 

 the skim milk undisturbed. Frequently the skimming was 

 not made until the milk had become sour, thus giving the 

 cream as much time as possible to separate. This method is 

 known as the SHALLOW SETTING METHOD. 



Several years ago the DEEP SETTING METHOD largely dis- 

 placed the shallow setting method in the better dairies. In 

 the deep setting method, the milk is placed in deep cans which 

 are usually placed in vats of cool water. By thus keeping 

 the milk at a low temperature, souring is delayed and, conse- 

 quently most of the cream has time to become separated while 

 the milk is still sweet and of much value as food for man and 

 his domesticated animals. 



A third method of cream separation is sometimes employed. 

 It is known as the WATER DILUTION METHOD. If fresh milk 

 is diluted by the addition of cold water (about half and half) 

 the cream separates much more rapidly. This method is not 

 often used because the separation of cream is not generally so 

 complete as in the case of the other methods, and because 

 the skim milk is so diluted that it is less valuable. 



622. Principle of the Cream Separation. In each of the 

 three methods of cream separation given, the difference in 



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