CHAPTER X. 



CREAMING MILK AT THE FARM. 



THE cream, which contains a large portion of the 

 fat of milk, is lighter, or is of less specific gravity, than 

 the serum or skim-milk, hence it tends to separate 

 from the heavier part. This separation, however, does 

 not take place unless force be applied. The two forces 

 made use of in creaming are gravity and centrifugal 

 the former in the case of milk set in pans or cans for 

 the cream to rise ; the latter in the case of centrifuges, 

 or cream separators. Both forces are natural and 

 have been in existence throughout all time, but only 

 the force of gravity was made use of for creaming milk 

 up to about 1876. The force of gravity is obtained 

 free of cost, hence the reason for its having been used 

 so long before centrifugal force, and also a reason for its 

 continued use by many. Gravity acts in a downward 

 direction upon the heavier skim-milk, while centrifu- 

 gal force causes the skim-milk to travel in an outward 

 direction in the bowl of the centrifuge. We have also 

 centripetal force, causing the cream to seek the centre 

 of the centrifuge or separator-bowl. The skim-milk 

 travels in the same direction as the centrifugal and 

 gravity forces are acting, while the cream travels in an 

 opposite direction 



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