Cream Separation 



1877 



a certain quantity of whole milk decreases in direct proportion to the in- 

 •crease of the amount of milk-fat in the cream. This fact is clearly brought 

 out in Figure 82. It should be noticed in Figure 82 that the weight of the 

 fat in the whole milk and in all three pails of cream was approximately the 

 same, but that there was a distinct variation in the weight of the cream. 



The rate of speed. — The centrifugal force that causes separation in the 

 modem separator is produced by the rapid revolving of the bowl. The 

 separator bowl about four inches in diameter makes approximately nine 

 thousand revolutions per minute. Thus a point on the circumference of 

 the bowl travels at the rate of somewhat less than two miles per minute. 



Fig. 

 the 



90° 80° 75 

 Separator 1 



90" 75" 70 

 Separator 2 



90° 8o° 



Separator 3 



90" 75" 



Separator 4 



90° 8o° 

 Separator 5 



84. — A diagram representing percentage of fat in skimmed milk as influenced^ by 

 temperature of the whole milk. Temperatures are expressed in degrees Fahrenheit 



The number of turns of the crank necessary to effect thorough separation of 

 milk varies for different machines from forty-five to sixty-five turns per 

 minute. A slight variation in the speed of the crank has a great effect on the 

 velocity of the bowl; and care must be exercised in producing a uniform 

 speed, if uniform results are to be expected. The effect of a decrease of 

 six or ten revolutions of the crank per minute on the percentage of fat 

 in the cream is considerable, as shown in Figure 85; and the effect on the 

 percentage of fat in the skimmed milk is very slight, as shown in Figure 86. 

 A slight variation in the speed of the crank does not affect the amount 

 of fat separated from the whole milk, but it does affect the quantity of 

 the cream separated. 



