480 



PARMER'S CYCLOPEDIA OF LIVE STOCK 



cream separation, the gravity and cen- 

 trifugal systems, both of which depend 

 for their results upon the difference in 

 the specific gravity between the fat and 

 other parts of the milk. There are 

 three modifications of the gravity system 

 in common use, namely, shallow setting, 

 deep setting, and water dilution. 



The shallow pan system consists in 

 placing the milk in pans 2 to 4 inches in 

 depth as soon as possible after milking 

 and keeping the milk at a temperature 

 of 40 to 60° F. in a room without dust 

 and without any bad odors. Under or- 

 dinary conditions it requires about 36 

 hours for the cream to rise by this sys- 

 tem and at the end of this time the 

 cream is removed by a milk skimmer, A 

 considerable amount of cream, on an 



tern of obtaining cream consists in di- 

 luting the milk with about an equal 

 weight of pure cold water, and leaving 

 the milk in tin cans for a few hours, at 

 the end of which time the skim milk 

 and water may be drawn away from the 

 bottom, thus leaving the cream. The 

 advantages of this system are that the 

 cream rises more quickly than by the 

 shallow setting or deep setting systems. 

 The method suffers from several dis- 

 advantages, however. It gives more vol- 

 ume to the milk to be handled and prac- 

 tically spoils the skim milk for feeding 

 purposes. Moreover, the cream is of a 

 slightly inferior quality and may be- 

 come badly contaminated if the water 

 used in dilution is not the best. 



The centrifugal separation of cream, 



Fig. 308 DOG POWER FOR RUNNING SEPARATOR 



average about .5 of 1 per cent remains 

 in the skim milk even under conditions 

 most favorable for the operation of this 

 system. 



Deep setting for cream separation 

 consists in placing the milk in shotgun 

 or Cooley cans about 8 inches in diam- 

 eter and 20 inches deep. The best re- 

 sults are obtained if the milk is kept at 

 a temperature of about 40° F. by plac- 

 ing the cans in ice water. Under favor- 

 able conditions not more than .2 per cent 

 of fat should remain in the skim milk 

 under this system and the cream is in 

 bettei condition than that obtained from 

 shallow setting. The time required for 

 the operation of this system is about 24 

 hours and the amount of fat in cream 

 obtained by the Cooley system is usually 

 18 to 20 per cent. 



The hydraulic or water-dilution sys- 



like the gravity systems, depends upon 

 the fact that the cream is lighter than 

 the rest of the milk, but the force 

 supplied for separating the cream oper- 

 ates in a horizontal direction rather than 

 in a vertical direction, as is the case 

 with gravity. Separation by the centri- 

 fugal method is accomplished through 

 the use of some form of separator. The 

 chief advantage of the centrifugal meth- 

 od is that the cream may be successfully 

 separated under a considerable range of 

 temperatures. Perhaps the best tempera- 

 ture is that of the normal body heat of 

 the animal, the milk being run through 

 the separator immediately after milk- 

 ing. A superior quality of cream can 

 be obtained by the use of a separator, 

 since the milk is not allowed to sour and 

 the cream is therefore not subjected to 

 the influence of bacteria which may 



