4 BULLETIN 196, U. S. DEPARTMENT OF AGRICULTURE. 
The effect of the sudden production of a vacuum, due to condensing steam inside 
the cans, may be seen in the strongly collapsed sides when they are played upon by 
a stream of cold water. Number 3 cans, if a little slack-filled, or gallons will present 
the appearance of being battered. If such cans, resting upon their sides instead of 
on end, so that the stream is along the upper side, are struck by cold water, the col- 
lapse at the one point may be so severe as to cause buckling or even breaking of seams. 
After the processing is completed, the pressure decreases inside the can until, 
theoretically, it becomes zero at the temperature at which the sealing was done and 
becomes a vacuum at temperatures below that point. As a matter of fact, however, 
a weak vacuum is always found at the temperature of sealing, due to changes in the 
product or to the action of the product upon the container in processing. Cans sealed 
at 160° to 180° F., and stored at from 60° to 80° F. will show a very strong vacuum, 
while those packed cold or nearly cold and stored in a warm place will show no 
vacuum and may show actual pressure, becoming springers. 
SANITATION. 
A modern cannery is no longer the rough, crude shed that once was thought to be 
sufficient for this purpose. First of all the location must be sanitary, away from 
manufacturing processes which of themselves are objectionable, such as soap making, 
tanning, rendering fats, or any other processes which may give rise to noxious odors 
or may be productive of organisms of decomposition. The yards and drives about 
the factory should be cleaned daily, and in summer dust should be prevented by 
frequent sprinkling or by the application of crude or specially prepared oil to the 
drives. The application of oil is especially to be recommended where there is much 
hauling and there is no pavement, or the factory is to be run for a short season only, 
as in the case of tomatoes. A single application made a couple of weeks before the 
season opens will suffice for several weeks; if the oil is put on early it will become 
incorporated in the earth and not be tracked into the factory to any great extent. 
The drainage must be such as to prevent any surface overflow from adjoining property, 
and also be ample to keep the stock in good condition at all times. It should be 
ample to care for the waste, as this is sometimes a serious problem. If the natural 
body of water available is not sufficient, settling tanks or filters may be necessary. 
Fermenting material, such as tomato trimmings or corn refuse, should not be tolerated 
within or near the factory. The supply of water should be sufficient for all purposes 
and of good quality; that used in washing, blanching, and brining should be free 
from excessive hardness or iron, otherwise the finished products may be damaged. 
If the water for this purpose is not naturally of the right quality, artificial treatment 
may benecessary. The water used for washing about the factory should have a good 
pressure for cleaning. A factory with a poor location, or an insufficient or poor water 
supply, has a handicap which is difficult to overcome. The facilities for bringing in 
or sending out stock should be ample, so that materials used need not be delayed, 
especially when it may mean deterioration. 
The buildings should be designed with reference to the special products to be packed, 
but there are some features which should be common to all. The ceilings of all rooms 
should be high, with ample provision for light and ventilation. The hght should 
come from numerous side windows, or, if the rooms are large, from turrets, or a saw- 
tooth-roof construction. Either of these two arrangements can be made to give a 
flood of ight and at the same time provide good ventilation. An advantage in the 
saw-tooth construction arises from the cooling and drying effect. When the straight 
section, or windows, is turned toward the north, the sun beating upon the southern 
incline will heat the layer of air underneath, causing it to rise. This creates a circu- 
lation within the room which tends to dry floors and tables and to lower the tempera- 
ture. Tests made in factories so constructed have shown several degrees lower tem- 
perature on hot days than was recorded in factories having the usual form of roof. 
