sr 
SWEETENED CONDENSED M1LK—CONDENSING 
use in the condenser. Under average conditions about fifteen 
pounds of steam pressure may be safely used. 
During the early stages of the process. when the milk is of 
low density, the evaporative duty ts high, probably about twenty- 
five to thirty-five pounds per square foot of heating surface with 
ten pounds of steam pressure. This gradualiv decreases and is 
lowest toward the end of the process. 
When enough milk is in the pan to completely cover the 
jacket and coils, the milk intake should he reduced and. regulated 
in accordance with the rate of evaporation. “The milk is drawn 
into the pan continuously, but only as fast as it evaporates. It 
should be kept as much as possible at a constant level, and this 
level is preferably as low as is consistent with complete covering 
of the upper most coil. 
In order to secure maximum rapidity of evaporation, the 
vacuum pump should run at the proper speed and its operation 
should be uniform, a uniform vacuum and temperature should 
be maintained and the milk should be prevented from rising to 
an abnormally high level in the pan. 
Prevention of Accidents.—The operator should pay strict 
attention to the pan in order to avoid loss of milk due to acci- 
dents. He should watch the water supply and govern its use 
accordingly. If the water supply becomes exhausted, air is lable 
to be drawn into the pan through the condenser. This will cause 
the milk to drop suddenly and then rise in a body, threatening 
to escape through the condenser. \Whenever air in considerable 
quantities is allowed to enter the pan while in operation, be it 
as the result of lack of water, or through any other cause, or 
when the vacuum pump is allowed to stop and lve steam is 
turned into the milk in the pan, as is the case when the milk 
is superheated. the escape of milk may be avoided by immediately 
shutting the steam inlet to the jacket and coils, by closing the 
milk intake and by slightly opening the blow-down valve when- 
ever the milk rises dangerously high. By skillful manipulation 
of the blow-down valve until the milk again settles down to 
uniform boiling, loss can be avoided and the process can be con- 
tinued in the normal way. 
