Examine rubbers to see that they are in place. Sometimes, if the
covers are screwed down too tight, the pressure of the steam from the
inside causes the rubber to bulge out. Simply loosen the cover a
thread or two, push the rubber back into place and then tighten. In
case the rubber does not seem to fit well or seems to be a poor
rubber, it should be replaced by a new one and the jar returned to the
cooker for five minutes.

The jars should be sealed tight--covers screwed down, clamps put in
place--immediately after they are removed from the cooker.

Invert to test the joint and cool. If the seal is not perfect, correct
the fault, and return the jar to the cooker for five minutes if hot,
ten minutes if jar is cold.

Do not invert vacuum-seal jars. These should be allowed to cool and
then tested by removing the spring or clamp and lifting the jars by
the cover only. Lift the jar only a half inch, holding it over the
table so that, in case the lid does not hold, the jar and contents
will not be damaged. Or, better still, tap round the edge of the
cover with a ruler. An imperfect seal will cause a hollow sound.

Tomato Purée. Small, misshapen, unevenly ripened tomatoes may be
converted into tomato _purée_. The tomatoes should be washed, run
through a colander to remove skins and cores, concentrated by cooking
to about half the original volume, and packed in the jars. Rubbers and
tops should then be placed in position and the product sterilized for
the same length of time as for canned tomatoes. _Purée_ even may be
kept in bottles sealed with sterilized corks and dipped several times