I noticed above that someone stated that you processed acidic foods in a water bath and you 'had' to process non acidic foods like meats in a pressure canner. I wonder when that 'had to' idea came into being. Most folks around here that are over 50 never heard of a pressure canner...
I think it went through a "it's a good idea to" phase first. That likely started when the home-grade pressure canner became available. It probably didn't hit the "you have to" phase until after the price came down and they became affordable.
I took some canned corn up to my grandmother this past summer and it bought me a valuable story:
When she left Kentucky in the early 1950s, they'd never heard of the pressure canner. They water-bathed their veggies, and the corn always worked out well, but had a short shelf life. She married my grand-father and they moved to Ohio where he could find work OTCM (other-than-coal-mining).
During the summers my grandmother traveled back to Kentucky to help with the harvest and putting up. When my granddad picked her up in the fall, most of the things she brought back with her did well. Except the corn. Within a week or two of getting it home, the corn started to turn. Her theory was that they had always water-bathed it and put it immediately, gently into their cellar, and the WB'd corn couldn't survive the long ride through the mountains on the rough roads of the time.
Not to be consoled, my grandmother was not going to live in Ohio with my granddad if she couldn't have corn from home. The corn in Ohio was "no good", and my grandmother wanted her corn from home. They were poor and really only grew dent corn (feed for their mule-tractor, they only kept what was extra according to how well the garden did that year), but it was my grandmother's favorite vegetable- but that is beside the point of the story. My granddad was going to lose his 16 year old bride to her mother's garden back home.
During their second spring in Ohio, my granddad had to go to Pittsburg for training for a couple weeks, and he came back with a pressure canner for his mother in-law- a VERY expensive thing at the time. That summer, my grandmother took it home, gave it to her mother, and they pressure canned that garden.
The corn survived, my grandparents stayed married, my mother was born, and...
Afterword
Because they were so expensive and rare, my great-grandmother's pressure canner earned local fame. From late summer through fall, it stayed on an almost permanent wood fire, canning vegetables from every garden in the holler. In the early seventies, when my great-grandmother stopped gardening, she brought the canner home with her to Ohio. Most of my baby food went through it. Grandma is slowing down, but she still uses it from time to time. The wife and I are the only canners in our generation of the family so, despite looking like its been through two world wars, we consider it an heirloom and know the sad day will come when we end up with it.
FIN
you're all welcome