When canning, you need to make sure that you choose the correct glass canning jars for the food that you are processing. There are a few things that you should know about them, as well as the lids and rings to assure success and safety.
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Glass canning jars come in many sizes, from half gallon all the way down to half pint (one cup). Some are more practical than others. Which size you choose depends mainly on what you are going to can and how it will be consumed. I use mostly plain pint and quart jars, but on occasion use half gallon and half pint jars as well.
Pints and quarts can be purchased in two designs - wide mouth which are about 3 1/4" across the top, and regular mouth which are about 2 1/2". There are advantages and disadvantages to each.
Wide mouth jars are easier to get food into and out of, as well as being easier to wash, because most people can get their hand inside them. They are wider across the entire jar, so you can fit less of them in your canner.
Regular mouth jars are more suited to juices, and sauces - things that pour out easily. Regular mouth pints are smaller around, so you can fit more of them in your canner at one time.
Most half gallon jars are wide mouth, and most half pints are regular mouth.
Food that you will consume in one sitting should be canned in jars that will give you one meals worth. For my family, a pint jar is the right size. If your family is bigger you might want to use the quart size though.
Food that you will open, refrigerate and eat out of for some time (pickles for example) may call for a larger jar. for my family the quart size is right. Unless you have a REALLY large family, I don't recommend using larger jars (half gallon or gallon) because they tend to be more expensive. It's probably more practical to open two quarts...
I do use half gallon jars to vacuum pack our home grown and ground corn meal to keep insects from getting in, and to keep the meal fresh. Jars that size are ideal for vacuum storing bulk dry goods to keep them fresh for long periods. It's nice to keep these bulky items out of your freezer too.
Half pints come in a lot of unique shapes, and the glass is often have a textured pattern for an "artsy" appearance. They are used mainly for jams, jellies and preserves. These small fry aren't really practical for general use, because they tend to be more expensive. They are most often used for gifts.
Most grocery stores and "big box" stores that carry other canning supplies also sell standard pint and quart canning jars in the spring and summer. It seems to me that many of them tend to sell out their stock or start packing them away in late summer - right about the time my garden starts bearing at it's heaviest!! So you might want to stock up early. You can also get them right here - look in the right side column of this webpage...
also keep my eyes open for auctions and yard sales selling used canning jars. If you buy them this way, they can be quite cheap, but you should to check them over very closely for cracks and chips before you try to use them. Since you don't know what was stored in them, wash them very thoroughly. The great thing about canning jars is, as long as you don't break or chip them, you can keep using them over and over and over again - The ultimate recycling. Try doing that with a tin can!!!
Nearly all new glass canning jars come packaged with lids and rings, so there's no need to buy them separately. If you are re-using jars, you will need new lids, and possibly rings.
Lids are officially called "Dome Lids". They are what actually seal the jars. You have to buy new lids every time you re-use jars for canning.
Heat and pressure cause the rubber compound inside the lids to deform during canning forcing it to take the shape of the glass jar. If you try to re-use them, there is a very good chance that most of your jars won't seal properly, because the top of the jar didn't line up perfectly with the deformation that was already in the lid.
Dome lids are cheap - don't try to skimp on this. Your family's health and safety aren't worth a couple of dollars.
Rings serve the purpose of keeping the lids tightly in place during canning process, until the lids seal. In fact, my mother used to take them off of the sealed jars before putting then on the shelf. I don't necessarily recommend this practice, but I believe that it can be safely done.
As long as your rings aren't rusty, you can use them over and over. Once they get rusted (and eventually they will), you need to replace them. If you use rusted rings, you run the risk of them not screwing down tight enough during canning. You can buy lid and ring combo packages fairly inexpensively as well.
Choose glass canning jars based on what you are canning and how many people you will be feeding. Different sizes are suited to different jobs, some are practical and some are not. Never try to re-use dome lids, and discard ring when they get rusted.