FARM DAIRYING 399 



be more than offset by the saving in time and labor of separat- 

 ing. In buying a separator, one should be selected which has 

 the reputation of being durable and capable of close skimming, 

 for the amount of fat left in the skimmed milk is a very im- 

 portant item. There should be no difficulty in operating any 

 of the standard makes of separators if the instructions accom- 

 panying the machine are followed. It should stand level on a 

 solid base and be operated at the speed indicated for the par- 

 ticular machine. It is absolutely essential that the separator 

 be kept clean and well sterilized in order to prevent the cream 

 being contaminated. 

 Variation in percentage of fat from hand-separator. 



There are a number of factors which affect the percentage 

 of fat in the cream and skimmed milk from a centrifugal separa- 

 tor. Many dairymen have the impression that the percentage 

 of fat should be constant, but this is not the case. The chief 

 factors affecting the percentage of fat in the cream are as 

 follows : 



1. Richness of the whole milk. 



2. Variations in the speed of the separator. 



3. Temperature of the milk. 



4. Rate at which milk flows into the machine. 



5. Adjustment of the cream screw. 



6. Amount of skimmed milk or water used in flushing the 

 bowl. 



Most of these factors are under the control of the operator, 

 and if milk from the same herd is used and all the other factors 

 are constant, the cream should not vary widely in its percentage 

 of fat from day to day. With most separators, the temperature 

 of the milk should be from 85° to 95° for the best results. If 

 the temperature is much lower than this, the separator may not 

 do good work, and a richer cream will be the result, but there 

 will also be a larger loss of cream in the skimmed milk. 



The proper speed for each machine is indicated on the crank, 



