46 Bulletin 151. 



Before calling attention to these tables in detail, a few words 

 •of explanation as to what is meant by efficient creaming may be 

 of service in helping to a clear understanding of the whole mat- 

 ter. The separation of cream from milk is always attended by 

 the loss of some fat which remains in the skimmed milk. The 

 less this fat is, . the more efficient the creaming and vice versa. 

 The percentage of fat in the skimmed milk is therefore the most 

 convenient measure of the loss that has occurred in any process 

 of separation. 



Centrifugal separators have been so perfected that the loss of 

 fat in the skimmed milk is reduced to a minimum, and for several 

 years it has been recognized by both manufacturers and users of 

 separators that the percentage of fat in the skimmed milk need 

 not be more than . i of i per cent, and in actual practice it is found 

 that there is seldom more than . 2 of i per cent in the skimmed 

 milk. When a gravity process, either deep or shallow setting, 

 is used the percentage is larger and considerably more variable. 

 When the conditions are all favorable the efficiency, particularly 

 of the cold deep setting, approaches the centrifugal separator, 

 but it is not infrequently in gravity creaming to find one per cent 

 or more of fat in the skimmed milk. 



In the summer of 1892 seventy farms were visited and the fat 

 determined of the skimmed milk at each place. On forty of 

 these farms shallow pans were used and on thirty a deep setting 

 sj'stem, in most cases theCooley, was in operation. The average, 

 results were as follows : 



Percent of fat in skimmed milk. 

 Lowest. Highest. Average. 



Forty farms using shallow pans 15 1.63 .39 



Thirty farms using deep setting 14 .60 .30 



We are now able to judge of the efficiency of these gravity 

 cans. It will be seen that in no case do they approach an}^ where 

 near the efficiency of the centrifugal separator and, in most cases, 

 the percentage of fat in the skimmed milk is decidedly more than 

 ■^A^ould be called good creaming by either the shallow pan or deep 

 setting process. In table I where " stripper " milk is used they 

 show an average efficiency about equal to the Cooley, but where 

 the milk of fresher cows were used (Table II) the Cooley gave 

 distinctlv better results. The tests made at the various farms 



