23 October 2012

Q & A: Care and feeding of home canning jars

The Rowhouse Livin' mailbag got the following question:

Q. How do you take care of your mason jars after you've used them?

For all practical purposes, mason jars last indefinitely if you take care of them properly. People on the Internet will tell you that they use 50-year-old jars all the time and haven't broken one yet. Anecdotally, the oldest jars in my own regular canning rotation are nearly 20 years old. Experts caution (PDF) that you shouldn't expect a jar to last more than 13 years. (My guess is that jars that undergo pressure canning year after year get worn out somehow with the stress, and they become more and more prone to thermal shock breakage.) But whether your jars last 50+ years or a mere 13 years, jar care starts as soon as you open them to enjoy whatever it was you last canned.

When removing food from a jar, use plastic or silicone utensils, or use very great care with your knife or spoon. Your goal is to avoid scoring or scratching the interior surface of the jar, with a mark you may not even be able to see, which can weaken the jar's integrity. A weakened jar can fail in your canner, especially in a pressure canner. And there are few sounds more disheartening than the thock of a jar blowing in the canner.

Once you've emptied the jar, fill it with water and let it soak for a few hours or overnight. No need for detergent; but be sure not to fill a hot jar with cold water, or vice versa. Then wash by hand with the rest of the dishes and let air dry.

I prefer not to put canning jars in the dishwasher, because I read somewhere that dishwasher detergent is bad for jars. Additionally, I prefer to really reach my (freakishly small) hand in the jar to feel for residue, and carefully visually inspect the jar after rinsing.

Remove limescale hard water deposits from jars by swishing some white vinegar inside and out, and then rinse with plain water.

Set the clean, dry jar upside down in your storage area. I've kept the cardboard boxes in which I purchased my jars, and use them to corral the jars in one section of my pantry cabinet. If cardboard is problematic for you -- for example, if your storage area is damp or you risk an insect or mouse problem -- then find some large, plastic storage totes. To avoid scratches and breakage, line the bottom of a tote with an old, clean towel; and place another towel between layers of jars if the tote is deep enough for you to stack the jars. Don't forget the lid! Finally, keep your boxes or totes in an area that's easily accessible. Make it so that it takes just a few seconds to carry a clean jar to the storage area, put the jar away, and close the box or tote. This way, home canning becomes an everyday part of your pantry strategy and housekeeping practice, not a tiresome chore that involves trekking to the attic or a dark corner of the basement.

In the end, the better you clean and store your jars, the less work you'll have to do when you take them out for use next canning season. Most manuals and web pages will tell you to wash the jars in hot, soapy water immediately prior to using them again -- but why? They were clean when you put them away! Unless you find evidence that mice got into your jars, just rinse them and heat them in the canner. (If you do find mouse issues, then by all means wash the jars, soak them in a bleach solution, and then rinse with plain water before using again.) So long as you process your food for at least 10 minutes, you don't need to pre-sterilize the jars.

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