256 THE BOOK OF BUTTER 



when heated over a low flame no bubbles of moisture and 

 air should leave the fat. The determination of the com- 

 pletion of the drying process is not difficult and a butter- 

 maker may soon learn by experience to recognize it. 



5. Put the cup in a desiccator or set it on a dry place 

 until the cup and fat have cooled. In the average 

 creamery where there is no desiccator, the cup should be 

 put on a dry shelf and a flat piece of paper placed on the 

 top of the cup. This paper should be sufficiently wide 

 completely to cover the cup and thus practically prevent 

 any moisture of the air from getting into the cup. A thin 

 aluminum cup will cool in about five minutes. It should 

 be weighed soon after cooling, unless it is in a desiccator 

 where the air is thoroughly dry. The reasons why the 

 fat and cup must be cooled are that the specific gravity 

 of the butter and cup increases as the temperature drops, 

 and thus they become heavier. A current of warm air also 

 goes up from the hot cup and butter, which causes them 

 to weigh lighter than when they are cool and no current 

 of air rising from them. When running a preliminary 

 churn test, the final reading may be obtained when 

 the cup and butter are hot. When this is done, a 

 correction must be made. In case a light aluminum cup 

 is used, the reading is likely to be .3 per cent higher when 

 the sample is hot than when it is cool. Thus a moisture 

 test that would read 14.5 per cent when just taken from 

 the flame would read 14.2 per cent when cool. This latter 

 reading would be the correct one. The reading of the 

 preliminary churn test when hot saves time, and it is 

 sufficiently accurate to be satisfactory at this stage of the 

 manufacture of butter. If a heavier cup is used, the 

 butter-maker may ascertain by a little experimental work 

 what the correction should be. 



