Jars should be examined after they have cooled, but within 24 hours
after processing, to be sure a seal has been obtained. To test a jar
that has a flat metal lid, press the center of the lid; if the lid is
down and will not move, it is sealed. Turn jars with porcelain-lined
zinc caps partly over in your hands; if they do not leak, they are
sealed.
When jars are thoroughly cooled, metal screw bands should be carefully
removed. Wipe outside of jars clean, and label jars to show date and
contents. Store in cool dry place. If you find a jar that did not seal,
use food right away or re-can the food immediately; empty the jar, pack
and process the food as if it were fresh.