You slave over a batch of jam, lovingly chopping the fruit and simmering it into sweet, sticky submission. At the end of a long canning session, you leave the jars with the rings on to cool on the counter, content in the knowledge that you’ve made enough jam to last until the following summer.
However, the next morning when you go to take the rings off, you find that they’re a little tough to turn. And what’s this? Black scum has formed around the rims of your jars! Oh no! Does this mean all your hard work is lost?
Happily, the answer to that panicky question is that the jars are perfectly fine, as long as the seals are still good. That black scum you see on the outside of my jars in the picture above is a result of a bit of blueberry jam (on the left) and white peach sauce (on the right) that siphoned out the jars during processing. It was trapped by the ring and left to sit for a day (sometimes it takes me a day or two to get around to removing the rings and labeling). During that time, that bit of jam and sauce reacted with the metal of the ring and formed that scum.
The way you handle a situation like this is simple. You just clean it off. Typically a simple wipe down with a sponge or damp cloth will remove any traces of it. However, if it’s resistant to removal, fill your sink with tepid water and let the jars soak for a few minutes. It should rub right off after that. Once the jars are clean, carefully dry them completely and gently, using the edge of the towel to wipe off that tiny bit of lid overhang.
Finally, when the jars are clean and dry, double check the seals to ensure that they’re still good. Make a thorough visual inspection to ensure you got all of it. Remember also to be careful when cleaning full, sealed jars as too much jostling and rough treatment can potentially break those carefully constructed seals. Oh, and while you’re cleaning your jars, do make sure to also clean the rings. They’ll have some of that residue on them and cleaning will extend their lives.
(I promised a few of you a Canning 101 post on pickling salt and how to substitute other types of salt in canning. I couldn’t quite get that post together tonight, but look for it next week.)