20 is shown one type of pressure cooker. It is provided with a bail, or
handle, for carrying it and with clamps that hold the cover firmly in
place. Attached to the cover is a steam gauge, which indicates the steam
pressure inside the cooker, and a pet-cock, which is used to regulate
the pressure. On some cookers, a thermometer is also attached to the
cover. Also, inside of some, resting on the bottom, is an elevated rack
for supporting the jars of food that are to be sterilized and cooked. In
operating a pressure cooker, water for generating steam is poured in
until it reaches the top of this rack, but it should not be allowed to
cover any part of the jars of food. Steam is generated by applying heat
to the bottom of the cooker, and the longer the heat is applied the
higher the steam pressure will go.

It is possible to secure a steam pressure of 5 to 25 pounds per square
inch in a cooker of this kind. This means that the temperature reached
will vary from a few degrees above boiling to about 275 degrees
Fahrenheit. At a pressure of 20 pounds, the temperature will be about
260 degrees. The heavier the material used for a cooker and the more
solid the construction, the higher may go the steam pressure, and, of
course, the temperature. Some cookers of light construction will not
permit of a pressure greater than 5 pounds, but even such cookers are
very satisfactory. It is the high temperature that may be developed in a
pressure cooker that greatly shortens the time required for cooking jars
of food and making them sterile.


CANNING WITH TIN CANS

46. For canning food in some tin cans, it is necessary to have a
soldering outfit for properly closing them. This consists of a capping