250 BUTTER-MAKING. 



METHODS OF PURIFYING WASH-WATER. 



There are two practical and effective methods of purifying 

 wash-water, viz., (1) Filtration, and (2) Pasteurization. Which 

 of these two methods is the most practicable and the most 

 effective in the creamery depends upon the conditions and 

 upon the quality of the water. In the case of water from deep 

 wells, which contains little or no organic matter, but at the 

 same time is infested with undesirable germs, pasteurization 

 is perhaps more expedient. Filtration, if the same degree of 

 thoroughness is to be reached as in pasteurization, is a com- 

 paratively slow process. Pasteurization of wash-water is a 

 trifle more expensive than filtration. Wash-water can be 

 pasteurized at the same time that the churning is being done, 

 thus economizing in time and fuel. Pasteurization is quite 

 effective in rendering the water germ-free, but it is not so 

 effective in removing any organic matter or other tangible 

 impurities which may be present. If the creamery does not 

 already have a pasteurizer, filtration can be employed very 

 profitably, and under average conditions it will perhaps give 

 the best results. 



Filtration. Filtration is inexpensive, and is a very efficient 

 method of purifying wash-water. It seems strange that bacteria 

 can be removed from water by passing through layers of sand, 

 gravel, coke, and charcoal, but such is the case. Filtration 

 is applicable to all kinds of water; even if the water appears 

 pure, it is well to. filter it. Fewer germs and fewer varieties 

 of micro-organisms are apparently found in deep well-water 

 than is the case in water from surf ace- wells; hence the ferments 

 which are present will have a free field for developing in the 

 absence of competing forms. If a sample of water which is 

 rich in micro-organisms is violently shaken with a certain amount 

 of charcoal, coke, chalk, or similar substances, and then left 

 for a time to settle, the pure layer of water at the top will be 

 almost entirely free from germs, and in some cases entirely 



