use new lids for canning! The problem isn't so much the potential for bacteria or mold ... that will be killed with sanitizing (washing with soap and hot water) and sterilizing ... the problem is that the sealing compound is not designed for multiple uses. Although some people have done it, and gotten away with it - why risk it?
You can reuse some, others you should toss. Those that are labeled Ball or Mason you can probably safely reuse for boiling-water canning, and possibly pressure canning - if you use new lids!. Some jars used in commercial processing are not designed for the rigors of water canning - they are chemically sterilized and filled at around 185ºF and not designed to survive multiple processings.
Originally Posted by AMSeccia
What about those new(er) white plastic (single construction) lids that Ball or Mason sells? I love those, but so far have only used for freezer jam. The box does not indicate they are for freezer use only.
If these are what you are talking about
read the label - it says, "Not for Processing. Ideal for Freezer Jams."