94 Milk and Its Products. 
manufacture is not affected either one way or the 
other by any of these three systems, so that their 
relative economy rests wholly upon the complete- 
ness, cost and ease of separation. 
Since the separation of cream from milk is al- 
ways attended with some loss of fat, it is pertinent 
to inquire as to the necessity of any separation of 
the cream when butter is to be made. It is per- 
fectly possible to manufacture butter directly, by 
churning whole milk without separating cream, and 
undoubtedly the first churns were skins of animals, 
into which the whole milk was placed and then 
agitated until the butter was brought; but under 
good conditions it is not possible to so completely 
remove the fat from the milk by a churning process 
as by a creaming process; so that while there is 
some loss in separating the cream, there is usually 
a greater loss in churning the butter from the whole 
milk. Even when the loss of fat in the butter- 
milk is no greater than the loss of fat in the 
skimmed milk, the greater amount of labor required 
to churn the whole mass of milk still renders cream- 
ing an economical practice in the manufacture of 
butter. 
Gravity creaning.—In separating cream by force 
of gravity, there is a greater loss of fat, a longer 
time required, and the various conditions affecting 
the milk have a greater influence upon the creaming 
than when centrifugal separation is used. The 
conditions of the milk that affect the creaming by 
the gravity process are: First, the size of the fat 
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