326 MILK AND CREAM TESTING 



ing the whirling process. Hot water in the machine is a 

 nuisance and does very little good. On the other hand, a little 

 kerosene stove arranged under the tester as shown in figure 106, 

 has been found to give excellent results, regardless of the tem- 

 perature of the work-room. 



Size. — A tester which will hold at least 8 bottles, or in case 

 of a herd of 15 or 20 cows, 12 bottles will be found preferable 

 to anything smaller. The slight increase in cost will be readily 

 made up by the increased rate with which the work is done. 



Speed. — The number of revolutions required to produce the 

 required force in the machine varies with its diameter. The 

 following table shows the number of revolutions needed for 

 machines when the revolving portion has the diameter indicated. 1 



Longer turning with lower speed will not produce the effect 

 of high speed. It will neither force the small fat globules out 

 of the bulb of the test bottle into the neck, nor will it squeeze the 

 water out of the fat, back into the lower portion of the bottle as 

 will be done with high speed. It is essential, therefore, that the 

 machines be placed on a thoroughly sound foundation and set 

 level and run at full speed. 



Temperature. — So necessary is it to have a reasonably warm 

 temperature in the machine that the power or factory-size 

 machines are usually provided with a direct steam inlet. Samples 

 may then be warmed before or during the whirling and kept hot 

 until the fat percentages have been read. With the hand machine 

 the same effect can be obtained by having a lamp placed as 

 previously described (Fig. 106). 



Care of the Machine — It may be almost useless to state that 



1 Testing Milk and its Products, Farrington and Woll. 



