EXPERIMENT STATION BULLETINS 207 



in tlie size of tbe fat globules in tlie milk, accompanied by an increase in the per 

 cent of other milk solids, attendant upon the advance in the period of lactation. 

 The smaller fat globules in a thicker tluid rise to the surface with greater difficulty. 



In some half a dozen trials, in which the milk of a single fresh cow was set by 

 itself, the skim milk showed the presence of only a trace of butter fat. At the same 

 time there was in the herd another cow, in the eighteen month of her period of 

 lactation, still giving a large tlow of milk. Milk from this cow set under the same 

 conditions in an equal number of trials showed a loss of over one per cent (1.08) of 

 butler fat in the skim milk. When the milk of this cow was set as a part of the 

 mixed milk of the herd, the can containing her milk showed an average loss in the 

 skim milk of eight-tenths of one per cent (.8) of butter fat. Bv diluting her milk 

 with ten per cent Its weight of water, about the same loss (.81) was suffered as 

 when mixed with the herd milk. When her milk was mixed with that of the fresh 

 cow above mentioned the loss of butter fat in the skim milk was reduced to about 

 a quarter of one per cent (.2(J). 



In trials of the cold deep setting method conducted Simultaneously with the 

 trials of the shallow pans heretofore mentioned the following losses were obtained: 

 In the fall trial, \Yheu the coves were all a long time in milk and the milk set for 

 only twelve hours 'in water varying from 34 to 54 degrees Fab. in temperature 

 averaging 45 degrees Fah.. the loss was a little over seven-tenths per cent (.73). 

 In th'e spring trial the milk set for twenty-four hours in water varying in 

 temperature from 41 to 52 degrees Fah.. averaging 45 degrees Fah., there was a 

 loss of a trifle over four-tenths' of one per cent (Al). From these results it appears 

 that, under what may perhaps be called average conditions as regards temperature 

 of water, setting milk for twenty-four hours gives much better results than setting 

 for only twelve hours. It also appears that setting milk in shallow pans for 

 twenty-four hours gives better results than setting in deep setting for twelve hours 

 under' the conditions existing in this experiment. 



It should be added that in the above trials the average loss was somewhat in- 

 creased by the skim milli being drawn off too closely in a few cases. Care should 

 always be taken to leave a certain amount of milk with the cream, as the top layer 

 of miJk always contains some butter fat. Then, too, as milk runs off from below 

 and the cream settles toward the bottom of the can unless the flow Is checked the 

 current of mdlk is liable to draw some of the cream out with it. 



37(6 seixirator.— The cream separator affords the most satisfactory means now in 

 vogue for getting cream from milk. The machine consists of a very rapidly 

 revolving bowl into which a continuous stream of wihole milk runs and out of which 

 continuous streams of cream and skim milk come. The rapid whirling of the 

 milk serves to separate the heavier from the lighter parts, and just as the lighter 

 cream finds its way to the top of the pan of milk when allowed to stand, while 

 the heavier part of the milk settles to the bottom, so in tbe rapidly revolving separa- 

 tor bowl the cream finds its way to the outlet near tbe center of the bowl, the skim 

 milk going to the outside. The operation is purely mechanical. 



Among the advantages of the separator over the shallow pan and cold deep 

 setting methods the following are to be considered: (1) The separation is practically 

 complete, the loss in the skim milk being seldom more than one-tenth of one per 

 cent, when the machine is properly handled; (2) The labor involved, it may be 

 safely said, is less than in either of the other methods; (3) The milk is separated 

 not only Avhile sweet, but when warm, the cream is sweet and of even thickness, 

 and the skim milk is in the best possible condition to feed to young stock as it comes 

 from the separator; (4) Instead of having all the milk from the herd to keep cool, 

 only the cream need be held at a low temperature, thus lessening the quantity of 

 ice required; (5) The thickness of the cream may be regulated. 



The main objection to the separator is the first cost. From the statements made 

 in the foregoing pages concerning the loss of butter fat in the skim milk where 

 gravity methods of separation are used, one who knows how much milk he gets dur- 

 ing the year can readily calculate whether or not it will pay him to invest in a 

 separator. 



In tlie use of the separatoi* three points should be carefully watehed and regu- 

 lated, viz.: the speed of the bowl, the temperature of the milk, and the feed of the 

 milk to the machine. With the same machine and all other conditions the same, 

 a greater loss of butter fat must be expected when the separator is not ran up to 

 speed, when the milk is below a certain temperature or when more than a certain 

 amount of milk is run through in a given length of time. 



