About six months ago, I salvaged a beautiful marinara sauce jar that I intended to refill with home-canned sweet pickles made using my mother’s recipe. And if I hadn’t taken a 12-week course to become a certified Master Food Preserver, I might have used that as a canning jar and possibly poisoned my whole family.
The glass jar has a classic shape and reads “Mason” on the side but it is, in fact, a faux Mason jar. And if you’re planning to do home canning that really matters.
A brief history of canning jars
The original Mason jar was invented by John Landis Mason in 1858, and its threaded top was a revolutionary concept in food preservation. Mason’s system was relatively cheap, easy to use and far less messy than the previously used method, which required sealing glass jars with a flat tin lid and sealing wax.
Unfortunately for Mason, he didn’t renew his patent after it expired in 1879, and he never made the fortune that I believe was rightfully his. In 1915, Alexander Kerr improved on Mason’s concept by inventing the two-part lid — a flat metal top with a rubber gasket that seals to the glass jar using a threaded metal ring. Nearly 100 years later, this is still the most widely preferred system for home food preservation.
All canning jars are not created equal
Mason-type jars are remarkably similar to commercial pint- and quart-size jars, like my marinara sauce jar. But there’s an important difference. Real Mason-type jars have a wider rim that gives them a better sealing surface. They are also tempered more than the jars that once held a commercially-canned product so they more easily resist cracking and breaking under the high pressure needed for pressure canning.
Real Mason-type jars have two types of mouths. A “regular-mouth” jar gets slightly smaller near the top. This “neck” helps hold the preserved food under the liquid level, which is imperative for proper food preservation. A regular-mouth canning jar cannot be used for freezing because the smaller neck doesn’t allow for the expansion of liquids as they freeze. A “wide-mouth” jar has straight sides, and it’s great for foods that might be hard to put in or pull out of a regular-mouth jar. They are also safe for freezing.
Just as there are different knives for cutting different types of food, there are also a variety of canning jars made to properly preserve different kinds of food. Here’s a rundown of the canning jars I have on my pantry shelves right now and the reasons I like each of them.
- Wide-mouth half-gallon jar: The National Center for Home Food Preservation recommends using half-gallon jars only for canning apple juice and grape juice. Because of their large size, these jars have poor heat penetration, and it’s impossible to ensure that the food in the center of the jar has been adequately heated. I use my half-gallon jars to store large quantities of cereal and pasta.
- Regular-mouth quart jar: This is perhaps the most versatile canning jar. It’s good for pickles, juices and most other sliced fruits and vegetables. It also holds just the right amount for use in a single recipe, especially if you’re pressure canning beans or tomatoes.
- Wide-mouth quart jar: This workhorse is ideal for large chunks of fruits and vegetables. Sadly, I’ve experienced more sealing failures with wide-mouth jars, but I like the idea that I could use them in the freezer if I wanted to.
- The commercial tomato sauce jar: This jar is not a real canning jar in spite of being labeled “Atlas Mason.” According to the center, this type of jar may be used with a two-part lid for canning high-acid foods in a hot-water bath, but there is a greater possibility of sealing failures and jar breakage. This jar also has a smaller neck than a regular-mouth quart jar, which makes it harder to fill. I use them for storing dry goods, but never for canning.
- Regular-mouth pint jar:This is one of the most widely used jars in my kitchen and all of mine are full of sweet pickles at the moment.
- 12-ounce jelly jar: This is smaller than a pint jar (16 ounces) so it’s perfect for gift-giving. You can give away a decent-sized amount of jelly, or anything else, without using up too much product in one jar. The decorative fruit pattern on the side of the jar makes it a “jelly jar,” but I refused to be limited by themed decoration.
- Half-pint jelly jar: This is my preferred jar for jams, jellies, preserves and fruit butters. Most of the recipes in my favorite preservation book of the moment, “So Easy to Preserve,” call for half-pint jars.
- Wide-mouth half-pint jar: I’ve inherited a few of these and they’re a nice shape, but they take up more room in the canner than the taller half-pint jars so I don’t use them too often for canning. They’re great for giving gifts of non-canned items, such as homemade goat cheese. (another obsession of mine).
- 4-ounce quilted jelly jar: This is the jar marketed as the “right size” for gift-giving. I disagree. It’s a very cute jar, but my friends complain that they don’t get enough jelly so I usually use the half-pint (8-ounce) or 12-ounce size instead.
These distinctions may seem obscure because a jar’s a jar, right? But John Landis Mason would disagree. So would the USDA. With the explosion in interest in home canning and the ever-present problem of botulism or simple spoilage, the difference between a regular-mouth quart and a faux-Mason jar may mean the difference between delicious pickles and a biohazard.
Photo: Pint jar of sweet pickles. Credit: Susan Lutz