74 



THE BOOK OP BUTTER 



that the weight of the fat in the whole milk and in 

 all three pails of cream was approximately the same. 



90° 80° 75° 90° 75° 70° 90° 80° 90° 75° 90° 80° 

 Separator 1 Separator 2 Separa- Separa- Separa- 

 tor 3 tor 4 tor 5 



Fig. 35. — A diagram representing percentage of tat in skimmed-milk aa 

 influenced by the temperature of the whole milk. Temperatures are 

 expressed in degrees Fahrenheit. Percentages shown at left. 



but that there was a distinct variation in the weight 

 of the cream. 



49. The rate of speed. — The centrifugal force that 

 causes separation is produced by the rapid revolving of 

 the bowl. The separator bowl, about four inches in 

 diameter, makes approximately nine thousand revolutions 

 a minute. Thus a point on the circumference of the 

 bowl travels at the rate of somewhat less than two miles 

 a minute. The number of turns of the crank necessary 

 to effect thorough separation varies for different machines 

 from forty-five to sixty-five a minute. A slight variation 

 in the speed exerts a great effect on the velocity of the 

 bowl ; and care must be exercised in producing a regu- 

 lated speed, if uniform results are to be expected. The 

 effect of a decrease of six or ten revolutions a minute on 

 the percentage of fat in the cream is considerable, as 

 shown in Fig. 36 ; and the effect on the percentage of fat 



