48 EQUIPMENT 
all use cold water or ice-water on the inside, 
and the milk flows over the outside. Properly 
operated, they are very effective, especially where 
large quantities of milk are to be cooled in a 
short time. The objection against them is that 
they are difficult to clean and sterilize properly. 
In small dairies such coolers are not so neces- 
sary as in large dairies. The small dairyman 
who has ice does not require an open cooler, 
