[I]n recent years I've learned that it can be hard on canning jars to constantly employ them for everyday use and then turn around and can in them. That's because when you eat out of jars and bang them around, it can weaken them and eventually lead to breakage in the canning pot.I'm 100% in agreement with Marisa, for my usual home economics types of reasons. Understand, it's not that canning jars are hard to replace when you lose them to breakage. Since so many people are home canning lately, more and more stores have them in stock on a regular basis. It used to be that if I needed a box of jars, I would have to plan a surgical strike at the hardware store at the very beginning of the summer garden harvest season. Now, however, I can find a few different types year 'round at my favorite kitchenwares shop in the 9th Street Market.
Nope, the issue is that canning jars are expensive. I mean, they're not expensive expensive. But they are a specialty item, and it takes time, effort, and cash to replace when they chip or break and can no longer be used for canning. Here's where I'm coming from. Anecdotally, canning jars can last for anywhere from a dozen years to decades. In my experience, two or three dozen of my jars have been used every year for about 15 years. But whether jars last 50 years or 15, you don't want to hasten the likely inevitable day when you hear that ominous thunk in the pressure canner that tells you one of your jars of green beans didn't make it. And one super easy way to hasten that day is to subject your canning jars to unnecessary scratches, bumps, clatters, and thermal shocks.
Which is exactly what you will do if, for example, you pour 7 ounces of hot dinner soup into a pint jar, screw a lid on nice and tight, slide the jar into the fridge, heat up the jar of leftovers in the microwave at lunch the next day, and scrape out every last drop with a metal spoon. Or fill a jar with ice, pour hot coffee into it, and stir in sugar and creamer for an iced coffee treat. (To be clear! I'm not saying Marisa was subjecting her canning jars to such ungentle treatment! I describe completely made-up, worst-case scenarios to emphasize my point.)
Now, I do use some canning jars for leftovers and for dry food storage. But I keep myself to some rules:
1. Keep canning-only jars and food-storage jars separate. After emptying and cleaning a canning-only jar, gracefully and lovingly replace it in the area in the pantry where the jars are stored by size. (I use the cardboard boxes they were sold in. This is not wise if you're in a climate where you get silverfish or other insects that would go after the cardboard, but it works for me.) After emptying and cleaning a food-storage jar, toss it willy-nilly on a shelf for ease of access, and check to see if some item doesn't now need to be added to the grocery list. Store food-storage jars with bands on them, for convenience, but do not do so with canning-only jars, to avoid rust.That last rule notwithstanding, I used to use jars for drinks -- I had a half dozen Classico pasta sauce not-quite-a-quart jars, which were a satisfying size for a glass of iced tea, and which fit my hands nicely. But though I have pals who have successfully home-canned with the jars, you really shouldn't; and I got a little weary of the hillbilly look on my dining table. I tossed them in the recycling bin as I replaced them, one at a time, with sturdy pint glasses and a lucky find of some French-made, molded-glass stemware.
2. Second-hand jars go into the food-storage category unless I am very, very sure about the jars' provenance. Were they loose on a thrift-store shelf? Did I spot them in a bin of free stuff on someone's stoop during sidewalk sale season? Or is it an unopened, completely unused box, albeit dating from the 1980s? I'll can with the last type -- in fact, I did, with my rustic honey-cran sauce this year -- but not with the others.
3. Food-storage jars may go in the dishwasher. Canning-only jars do not, because dishwashing machine detergent can adversely affect home-canned foods.
4. Metal scraping utensils are always OK for food-storage jars. They are never, ever OK for canning-only jars.
5. Do not use a new, unused lid for leftover or dry food storage. That would be a waste of money (lids seem to increase in price by about $0.20 per box every year). Use one of the used lids kicking around in the utensil drawer, instead.
6. Do not use any jars for consuming beverages.
Though when all was said and done, I did keep two 8-ounce Classico pesto jars, for those chilly winter nights when I want to kick back with a wee dram.