74 



THE BOOK OF BUTTER 



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

 all three pails of cream was approximately the same, 



.26 



.18 



.16 



.14 



.12 



.10 



.08 



.06 



.04 \ 



.02 



.00 



90 80 75 

 Separator 1 



90 75 70 

 Separator 2 



90 80 

 Separa- 

 tor 3 



90 75 

 Separa- 

 tor 4 



90 80 

 Separa- 

 tor 5 



FIG. 35. A diagram representing percentage of fat in skimmed-milk as 

 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 



