For steam-pressure and pressure-cooker canners the following precautions should be observed: 

1.  Lower the inside crate until it rests on the bottom of the steam-pressure canners.  In the case of the pressure cooker put the rack in the bottom of the cooker.

2.  Have the water come to, but not above, the platform.

3.  Tin cans can be piled one above the other.

4.  When the canner has been filled fasten the opposite clamps moderately tight.  When this has been done tighten each clamp fully.

5.  Have the canner absolutely steam-tight.

6.  Allow the pet cock to remain open until live steam blows from it.

7.  Close the pet cock.

8.  After the gauge registers the correct amount of pressure, begin counting the time.

9.  Maintain a uniform pressure throughout the process.

10.  When the process is completed allow the steam to escape gradually through the pet cock.  You can lift the pet cock slowly, using a pencil or a knife.  This can be done only with tin cans.  If glass jars are used the canner must be cooled before opening the pet cock.  Blowing the steam from the pet cock is likely to cause a loss of liquid from the partly sealed glass jars.

11.  Throw the tin cans into cold water.

12.  If tin cans bulge at both ends after they have been completely cooled, it indicates that they are spoiling and developing gas, due to bacteria spores or chemical action.  These may be saved if opened at once and resealed or resoldered and processed again for ten minutes.

The following table will help you in estimating how many cans of fruit and vegetables you will obtain from a bushel of product: 

NUMBER OF CANS A BUSHEL FILLS

NO. 2 CANS     NO. 3 CANS
Windfall apples                 30             20
Standard peaches                25             18
Pears                           45             30
Plums                           45             30
Blackberries                    50             30
Windfall oranges, sliced        22             15
Windfall oranges, whole         35             22
Tomatoes                        22             15
Shelled Lima beans              50             30
String beans                    30             20
Sweet corn                      45             25
Peas, shelled                   16             10

CHAPTER X

INTERMITTENT CANNING OR FRACTIONAL STERILIZATION

In some parts of the United States, particularly in the South, such vegetables as corn, beans, peas, squash, spinach, pumpkin, etc., are canned by what is known as the fractional sterilization, or the so-called Three Days Process.

Southern canning experts have had trouble with certain vegetables, such as those named, when they canned these vegetables in the wash boiler by the cold-pack or one period method.  They say that the climatic conditions are so different in the South that what is possible in the North is not possible in the South.