26 
BULLETIN 973, U. S. DEPARTMENT OF AGRICULTURE. 
it and the cheesecloth folded over it. Another rack is then placed 
over the whole. The filter is then attached either to the dumping 
device or to the receiving tank. It will be necessary usually to change 
the filter during the day (depending on the quantity of milk handled), 
as the cotton will become filled with dirt; also, if care is not taken, 
the cotton may get out of place so that some of the milk will pass 
through without going through the cotton. The cheesecloth must be 
thoroughly washed and sterilized after each use, and kept in a clean 
place. It can be used several times before it is thrown away. The 
cotton should be thrown away after it is used once. The milk 
should pass through the various pieces of apparatus with as little 
exposure to the air as possible; and after pasteurization, cooling, 
and bottling it should be kept in the cold-storage room until taken 
Fig. 18.— Cleaning a milk cooler in a large plant. It is later steamed. 
to the delivery wagons. It is very essential that the milk be cooled 
to 50° F. or below and held there until delivered to the consumer. 
As soon as the milk is put up, all parts of the apparatus should be 
cleaned thoroughly by first rinsing in cool or tepid water, then wash- 
ing with hot water to which washing powder has been added, and 
finally sterilizing with boiling water or steam. (See Fig. 18.) After 
the milk has passed through the apparatus it is a good plan to pump 
cool water through the entire system first, and then hot water to 
which washing powder has been added. The pumps and pipes can 
be rinsed by pumping water through them immediately after using. 
They should then be taken down and thoroughly washed, which can 
easily be done if there are frequent hand couplings in the pipes. 
After washing and rinsing the pumps and pipes they should be steril- 
