The Mason Jars You Should Never, Ever Use For Canning

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While the hobby of canning saw an increase during the COVID-19 pandemic lockdown in the U.S., the pastime has stuck around. A search for canning on both Instagram and TikTok reveals nearly 2 million posts combined. Driving reasons behind the uptick range from worries about food security and food additives to concerns over food waste and sustainability. But these good intentions don't mean that Americans are canning correctly or even safely. It turns out that reusing commercial product jars such as those with "Atlas" or "Mason" marked on them (used for Classico sauces) is not advised by the manufacturer. Doing so could lead to disastrous consquences.

"Atlas" and "Mason" markings on popular commercial jars — like those Classico pasta sauce jars — do not mean that the jar is fit for reuse in home canning. The truth is that those labels are basically decorative. In fact, on Classico's website (it's a Kraft Heinz company), an old FAQ page shut down the question, stating that its jars were not suitable for home canning because a coating is applied which could lead to scratches and breakage. It also noted that the jars are too light to be safe for the process. Finally, food preservation specialists at the University of California Agriculture and Natural Resources note that if you continue despite the warnings, these jars should only be used in water or steam canning and never in pressure canning. 

Unfortunately canning social media posts don't always give safe advice. Add to that that we don't always follow guidelines well anyway and problems occur. In fact, a University of Nebraska Extension Educator Brenda Aufdenkamp told NPR member station KBIA that Americans tend to "skip over things or don't think it's that important" (referring to steps in recipes and processes). One of those steps is using the wrong jars. While some people have seen success in reusing commercial product jars such as pasta sauce jars, they are not built to withstand serious heat.

While the National Center for Home Food Preservation says you "may" use "most" commercial jars — with new two-piece lids — it also says you should expect these jars to break. While we know we should never reuse canning jar lids, seal failures and breakage when using these jars even with new lids is more likely for a few reasons. Commercial jars have a narrower sealing surface, meaning that even if those new lids seem to fit, they likely won't achieve the seal necessary to preserve food. Additionally, the glass isn't tempered the same way as proper Mason-style canning jars, so many will break with the pressure. Basically, there are downsides to canning at home. Even insignificant scratches could dangerously impact the sealing process. And with preserved food, sometimes you don't know you did it wrong until you get sick, according to Aufdenkamp.

Ultimately, the only safe ways to reuse commercial jars are to store dry goods or as fermentation containers — and, even then, they still require appropriate seals. You're better off buying wide-mouth Mason jars specifically designed for canning, like this set of 12 from Amazon.