DAIRYING 33 



on the market makes it impossible to describe them all, but some 

 have stood the test of years and proved their superiority. 



The number of hollow bowl machines now on the market is 

 not large, but some of these are as satisfactory as those filled with 

 discs or plates. 



28.1. The discs in a separator bowl divide the milk into 

 thin layers and subject it gradually to the action of the centrifugal 

 force. This reduces the power required to turn the bowl of a 

 given capacity and it also reduces the length of time necessary 

 to subject milk to the centrifugal force in order to give a satis- 

 factory skimming. The discs may increase the capacity of a 

 bowl about three times over that of the same bowl without discs. 



282. The time milk remains in a separator bowl may be 

 calculated from the amount of milk it holds and the amount 

 skimmed per hour, e. g., if a bowl holds 10 pounds of milk when 

 rilled and its capacity is 3000 pounds per hour, or 50 pounds per 

 minute, milk must remain in the bowl about one-fifth of a minute, 

 or 12 seconds, during the process of skimming. 



283. The development of the cream separator may be seen 

 from the following results * obtained in Germany, where several 

 tests were made of machines from year to year. The average 

 per cent, of fat in the skim milk in 1894 was .19; in 1898, .22; 

 in 1900, .16, and in 1904, .11.** 



284. Further reduction in the amount of fat left in the skim 

 milk can hardly be expected, but the capacity of the bowls may 

 be increased by greater speed as stronger material may be found 

 from which to manufacture the bowls. 



Cream separators may be classified first, according to the 

 method of attaching power to the bowl, such as belt, turbine, and 

 crank or cog gearing attachments, second as hollow or filled with 

 discs or plates, third, bowls with or without a spindle, fourth, sus- 

 pended bowls. 



* Kirchner Milchwirtschaft. 



** These tests of skimmed milk were not made by the Bab- 

 cock test. 



