Once you understand the best practices of safe canning, you realize that not every jar should be used for food preservation. In fact, I tell my canning students that there are three types of canning jars to avoid (for canning purposes, of course).
1. Family Heirloom Canning Jars. First of all, there are some jars we may have that belonged to our relatives – blue glass, green glass, square, whatever – these jars (unless they are the new throwback blue and green ones) are best used for decorating and storage. Many of them are nicked or have chips in the rims, and most importantly, after years of use, the stress of submerging the jars in hot water has weakened the glass to the point that you may experience breakage.
2. Antique Canning Jars. You also can find lots of canning jars at sales, flea markets, and garage sales. These too, are not the best idea. Even though the cost is usually right, you have no idea of how they were stored, and again stress on the glass from canning, and some that have experienced freezing temperatures, can cause failures and who wants all of their hard work to be ruined when a jar breaks?
3. Commercial Food Jars. Other jars to avoid – glass mayonnaise, salad dressing or other jars that have held commercial products. These are “one time” use jars and have seams and weak spots that may also result in breakage. Use them for crafts and storage but not for home food preservation.
Tip: Long live the Canning Jar – Lifespan matters
The life span of jars will depend on how you treat them. If you are careful and store them at the right temperatures and treat them well, you can expect them to last a good long while. On the other hand, if you bump hot jars together during the canning process or store them without some packing, expect them to have a shorter life.
Tip: The scoop on lids
While looking on the web at canning supplies, I have found lots of different shapes of jars and I think “gee those are cute” but then I think they are expensive and may not be made to fit the standard lids that are available. Also, I see some of the lids that require the old rubber gasket – these are not appropriate for modern canning either. One-piece lids? Not for the home canner. Since one of the principles of home canning is to allow the air to escape from the jar creating a vacuum-type seal, we need to use two-piece lids that will allow the air to escape.
Tip: Buy Made in the USA for Safest Canning
When buying jars, I suggest buying those made in the USA because they are manufactured to USDA standards and will withstand the temperatures in a pressure canner. Prices vary according to where you purchase them, but if you watch, sometimes stores run specials on them which helps with the cost. I also suggest not buying the box store brands of jars – I personally had seal failures and heard of many folks who also had problems with them. And when they sealed, I thought the jars were breaking!
I know this is a lot of information about jars but when I spend the time preparing the food and processing it, I want something with a good seal that I know will last for at least a year (unless it is eaten first!).