230 DOMESTIC ANIMALS, DAIRYING, ETC. 



succeeding milking is run through the separator the cream neces- 

 sarily becomes contaminated with the bacteria causing this decompo- 

 sition, and tainted with the products of decay. This cream is both 

 dangerous to the health of the consumer and unfit to be made into 

 butter. The hygienic and sanitary side of this practice is sufficient 

 to condemn it. In addition to this the use of unclean separators 

 also causes a material increase in the per cent of fat in the skim milk. 

 The presence of these remnants of milk in the bowl and in the cream 

 and skim milk outlets obstructs the free passage of the milk and hin- 

 ders the process of separation. 



Condition of Milk. The freshly drawn milk is in the best con- 

 dition for effective skimming. It has the proper temperature, the fat 

 is in solution and the physical condition of the milk is such as to 

 insure a high degree of fluidity. Sour, curdled milk skims with dif- 

 ficulty. Before such milk is run through the separator it should be 

 poured from one can to another in order to break up the curd as 

 finely as possible. Unless this is done it will cause the machine to 

 clog. The clogging can be prevented more or less by underfeeding 

 the machine. It cannot be expected, however, that the separation of 

 sour and curdled milk will be complete. 



Temperature of Milk. The warmer the milk the more fluid it 

 becomes, and the greater the freedom with which the fat globules 

 can move about. The more fluid the milk the more complete is the 

 separation. 75 deg. F. is about the minimum temperature at which 

 most separators will skim closely. At 60 deg. F. there is a decided 

 loss of butter fat in the skim milk, no matter what make of hand 

 separator may be used. On the farm the best results are obtained, 

 where the milk is separated as soon as it is drawn. It has then an 

 ideal temperature for skimming. If the milk is separated but once a 

 day, the cold milk should be warmed up before it is run through the 

 separator. 



Rate of Inflow. Every separator is built to take care of a cer- 

 tain amount of milk. It has a certain capacity. The capacities of 

 the hand separators used on farms range from 250 to 900 pounds of 

 milk per hour. When the machine is forced beyond its capacity, the 

 milk has to pass through the bowl so fast that it is not exposed to the 

 centrifugal force long enough to effect a complete separation of the 

 fat. The more milk that is run through the separator in excess of 

 its given capacity, the greater the loss of fat in the skim milk. It is, 

 therefore, of importance that the operator know the exact capacity of 

 his machine and then govern the inlet accordingly. 



Richness of Cream. The thickness of cream obtained from cen- 

 trifugal separators is regulated by the cream screw. It is affected too, 

 to a greater or less extent, by most, if not all of the conditions which 

 influence the per 'cent of fat in the skim milk, and which have been 

 above referred' to. While most of the standard makes of separators 

 will do good skimming if cream is produced that tests from 20% to 

 50% of fat, there is a considerable difference in the behavior of dif- 

 ferent machines. Some separators skim as closely when 50% cream 

 is produced as when set for 30%. Others are at their best when set 



