168 DAIRY FARMING 



rator out of plumb, (3) dirty oil or dirty bearings, (4) 

 unstable foundation, or (5) unbalanced bowl. 



C. The best skimming is not possible with any sepa- 

 rator when the temperature falls below 60 F. A tem- 

 perature of 85 to 98 F. is the most satisfactory for 

 ordinary skimming. Under some conditions the cleanest 

 skimming is obtained at temperatures above 100 F. The 

 reason milk separates better at the higher temperatures is 

 that the viscosity is reduced. 



D. Sudden heating tends to increase the loss of fat 

 in skim-milk. The reason for this is that the fat heats 

 more slowly than the milk serum, which diminishes the 

 difference between their densities. When, for example, 

 milk is suddenly heated from near the freezing tempera- 

 ture to 85 F. by applying live steam, the loss of fat in* 

 the skim-milk may be four times as great as it is under 

 favorable conditions. 



E. Unduly crowding a separator increases the loss 

 of fat in the skim-milk. On the other hand, a marked 

 underfeeding is apt to lead to the same result. 



F. The higher the acidity of milk the poorer the 

 creaming. With sour milk the loss of fat in the skim- 

 milk becomes very great. 



G. Sometimes large numbers of undesirable (slimy) 

 bacteria find entrance into milk and materially increase 

 its viscosity. This results in very unsatisfactory creaming. 

 Low temperatures also increase the viscosity of milk 

 which accounts for the poor skimming at these tempera- 

 tures. 



H. Most of the standard makes of separators will do 

 satisfactory work when delivering cream of a richness of 

 $0%. A richer cream is liable to result in a richer skim- 



