46 DAIRYING 



302. These figures show a difference in the per cent, of fat 

 in the skim milk of .18% (.03-.21) between normal speed and 20 

 turns of the crank below normal speed. This is a loss of one-fifth 

 of a pound of butter in each 100 pounds of milk skimmed or at 

 least 5 cents worth of butter per 100 pounds of milk. Calculated 

 on the basis of 8000 pounds of milk per cow per year, the loss 

 amounts to $40 for a herd of 10 cows, or about one-half the price 

 of the machine, and with the herd of 20 cows, the loss would be 

 equal to the cost of some separators when new. The figures show 

 that it pays to give attention to the speed at which the separator 

 is run every day. 



303. The speed of the turbine separators is somewhat regu- 

 lated by the pounds of steam pressure shown on the steam gauge, 

 but frequent use of the speed indicator is always advisable. A 

 variation in speed affects both the cream and the skim milk. Too 

 low speed tends to thin the cream and enrich the skim milk, 

 while too high a speed will thicken the cream and diminish the 

 per cent, of fat in the skim milk. Variations above and below 

 normal speed during one run are very wearing on the machine 

 as well as expensive in losses of more or less butter fat. It should 

 also be remembered that there is a limit to the strain which the 

 separator bowl will endure without bursting, and on this account 

 the speed of the separator bowl should be carefully watched. 



Skimming Temperature of the Milk. 



304. The temperature to which the milk is usually heated for 

 cream separation ranges from 75 to 85 degrees F. When cows 

 are receiving a large amount of green feed and when they are fresh 

 or producing a large flow of milk, the cream is separated easier 

 than is the case with milk from strippers or from cows receiving 

 dry feed exclusively. 



These two factors, the feed of the cows and their period of 

 lactation, have an influence on the temperature to which milk may 

 be heated before separation. When many cows are fresh a tem- 

 perature of 75 degrees F. is often high enough for the milk. Dur- 

 ing hot weather it is the custom at some creameries to skim the 



