CREAM SEPARATION 77 



smaller is the variation of the fat-content. The difference 

 in the percentage of fat is not so great from day to day as 

 it is from milking to milking, and this variation is still 

 less from week to week and from month to month. The 

 influence of a variation in the fat-content of the whole 

 milk on the percentage of fat in the cream is shown in 

 Fig. 38. The percentage of fat in the cream is in almost 

 direct proportion to the percentage in the whole milk. 



51. Variation in the quantity of whole milk or in the 

 amount of liquid used for flushing. There is variation 

 in the quantity of milk from one milking to another, and 

 this causes variation in the amount to be separated 

 from one time to another. Very few persons operating 

 separators use a fixed amount of skimmed-milk or water 

 for flushing the separator bowl. For the hand ma- 

 chines, two or three quarts of flushing material are 

 sufficient. For the larger power separators, more milk 

 is usually separated ; consequently, there is more cream 

 and it is possible to use more skimmed-milk or water in 

 proportion to the size of the separator for flushing without 

 very great dilution of the cream. The amount of flushing 

 material that goes into the cream is only a small percentage 

 of the total, and it affects only slightly the percentage 

 of fat in the cream. Under average conditions, these 

 factors are not of much importance if approximately the 

 same quantities of milk and flushing material are used 

 each time. 



52. Slime deposit. If the passages for the cream and 

 the skimmed-milk in a separator are closed or partly 

 so by slime deposit, the efficiency of the separator is 

 affected. This slime deposit is composed of fibrin from 

 the milk and of dirt, and it accumulates in a greater or 

 less amount even from the best milk. Generally, this 



