A Canning Jar is a Canning jar? Right?

canning jars1Nope. Wrong. Not all “canning jars” are created equal.

Canning jars, sometimes called Mason jars, are a hot trend these days. They are everywhere – from a rebirth of home canning to decorations for weddings and picnics and even countertop storage for small items.

True canning jars are made of heat tempered glass to allow them to withstand the high heat involved in the canning process. Some are even safe to place in the freezer (for freezer jam or freezer slaw). Traditionally, canning jars are sold in cases of 6 or 12. They come in sizes of 4 ounces, 8 ounces, 12 ounces, 16 ounces and 32 ounces. They have 2-piece metal lids and are carefully made to ensure a flat smooth rim on the jars.

While I am often asked about canning with other types of jars, these are not recommended as the National Center for Home Food Preservation reports these jars are more likely to result in seal failures and jar breakage. The reason? The National Center provides this explanation: “These jars have a narrower sealing surface and are tempered less than Mason jars, and may be weakened by repeated contact with metal spoons or knives used in dispensing mayonnaise or salad dressing. Seemingly insignificant scratches in glass may cause cracking and breakage while processing jars in a canner. Mayonnaise-type jars are not recommended for use with foods to be processed in a pressure canner because of excessive jar breakage. Other commercial jars with mouths that cannot be sealed with two-piece canning lids are not recommended for use in canning any food at home.”

I would also be hesitant to home can in jars that are sold new in singles and doubles. Even though I have seen jars like this called “canning jars”, it is difficult, if not impossible, to determine they are made from tempered glass. These other jars still have many uses – just not canning. They are great for storing liquids and soups in the refrigerator. You can make layered baking or drink mixes in them; store dry goods like pasta, beans or chocolate chips; use them to store small kitchen gadgets; use a grouping of jars to store cotton swabs, cotton balls and other toiletries in the bathroom. The list goes on . . .

In case you are wondering, in the photo above, the only one of those five jars that is definitely a canning jar is the little jelly jar, second from the right.

Author: Kate Shumaker, Extension Educator, Family and Consumer Sciences, Ohio State University Extension.

Reviewer: Christine Kendle, Extension Educator, Family and Consumer Sciences, Ohio State University Extension.

Photo Credit: Kate Shumaker

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