At one of the communities I lived at, we would can over 1,000 jars of various things per season, both in boiling
water and under pressure. We put the idea to the test about using other jars than bona-fide canning jars, and found after repeated uses that these other jars work fine, provided they will fit a canning jar lid and ring. No more of them broke or failed to seal than the brand-name jars. Things like mustard, mayonnaise, tomato sauce, and various jams and jellies are frequently sold in jars that will fit a canning jar lid. If you are lucky
enough to live somewhere with a recycling center with open bins, you can learn to recognize these and scrounge them in quantity pretty quickly. I'm still using a collection of several hundred jars largely obtained this way. If those jars have stuck on labels and old encrusted nasty food residue, I found they could be cleaned easily by means of what I called "the long soak"---sinking them down on top of each other in a barrel of water, and then adding floating plants, mosquito fish, etc. and basically allowing a
pond ecosystem to
feed off of them for a year or so. After this time, most would wipe and rinse clean!
