250 BUTTER-MAKING. 
MetuHops or Puriryinc WaASH-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 surface-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 
