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Canning Jars Questions and Answers!

Canning jars are different from other food jars, and there are many unusual questions people have about canning jar usage.  Here is a collection of popular and common questions about selecting, finding and using canning jars. See this page for questions and answers about the lids, rings and attachments to canning jars (rather than the jars themselves). This page has a history of the canning jar and this page has free label templates to allow you to make your own custom jar labels.. Also see this page about why jars don't seal and how to correct it.

How can I tell if my jars have sealed and whether they have spoiled?

That requires a detailed answer.  See this page: How can I test or examine my jars to see if they sealed properly or have spoiled?

Can I use empty mayonnaise and spaghetti jars that have threads to use the same size rings and lids as Ball jars?

See this page for the answer. (too much to put on this page)

I am looking for jars that have at least one side that is not embossed with either a company name or some other decoration. It just does not look very professional to place a label on top of a cluster of fruit/veggies. Do you know where I can get either plain jars or jars with at least one side that is plain?

Yes. I found that the "Golden Harvest / Mason" brand of canning jars only have their raised logo/words embossing on 1 "side" or face of the jars - in other words, 3/4 of the jar is smooth.  I have found them in Big Lots, sometimes groecry stores and big Box store.  And online (see the ad at right - buying them here does contribute to this website, by the way!)

How would you go about using non-canning jars for canning sauce ? In other words, not using mason jars but other jars with screw on lids? Would you go about it the same way or is there a different way? My concern would be the lids and having them sealing properly.

Well, the "authorities" all say NEVER use anything but Ball / Kerr and other canning jars. In practice, many home canners find (through practice) that certain products (like Classico brand spaghetti sauce) are packaged in jars that are the same specification as commercial home canning jars.

And that's about it- it the lid and ring fits and the lid seals, the only other concern is whether the glass is thick enough to withstand the usual home canner banging it around. I've had a few "Miracle Whip" jars break, so I don't use those anymore, but the Classico's work fine for me. I don't recall ever having one break on me in the past 25 years. Note that the Classico's manufacturer does not recommend reuse of their jars: here is what they say on this page:

 "Can I reuse the Classico jar for home canning?
No. A coating is applied at the glass plant to reduce scratching and scuffing. If scratched, the jar becomes weaker at this point and can more easily break. This would increase the risk of the jar breaking when used for canning. Also, the lighter weight of our current jar could make it unsafe for home canning. "

Stuck lids on new jars - I just purchased a dozen Kerr 1/2 pint jars with lids. When I was getting ready to wash the jars I noticed that the lids were fairly difficult to get of the glass. They are new and so are the lids however I am concerned that the lids have a dent in the rubber(?) or sealing part. Can they still be used?"

I've noticed that, too, from time to time. They were probably stored in a hot warehouse or on a hot truck. But, after I pried them off, I've never had a problem with the jars failing to seal properly, so I'd say go ahead and use them.

A neighbor generously gave me 2 boxes of canning jars that are the old fashioned glass top with a wire on the top (lightening jars perhaps?) There isn't any rubber gasket on these and I wondered if I should try to find them in the store or if the jars should be reserved for non-canning uses, like dry food storage or decoration. Do you recommend using these old jars or should I keep to my typical top and ring jars

Stick to the lid and ring types. The others leak and spoil at a noticeably higher rate. They're not really safe for vegetables.  The type with the glass lid with a gas and a wire to hold it down works ok for jam, since jam doesn't spoil as readily and is high in acid. But, really, they're only for decoration these days.  The Ball/Kerr/Mason ring and lid types are SO much more reliable and safer.

I have the opportunity to buy the wire-bail-top canning jars (described in the previous question) VERY inexpensively about the price of the ball jars and lids regular mouth. I need to ensure I can use these in food canning. These are not previously used, but I can't find online instructions for canning with them. Help?

Instructions, aside from sealing / closing the jars, they're the same as other jars. You just need to be scrupulous about wiping the sealing surfaces before closing the lid after filling, and making sure it seated properly.

What causes jars to break in a canner?

Breakage can occur for several reasons: 1. Using commercial food jars rather than jars manufactured for home canning, 2. Using jars that have hairline cracks, 3. Putting jars directly on bottom of canner instead of on a rack, 4. Putting hot food in cold jars, or 5. Putting jars of raw or unheated food directly into boiling water in the canner, rather than into hot water (sudden change in temperature-too wide a margin between temperature of filled jars and water in canner before processing).
See this page for more information!

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How can I remove scale or hard-water film from canning jars?

Soak jars for several hours in a solution containing 1 cup of vinegar and 1 gallon of water.

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What can I process in half-gallon canning jars?

One or more canning jar manufacturers are selling half-gallon canning jars. One manufacturer has a printed note on the top that says half-gallon jars are only used for some highly acidic foods in a boiling water canner.

The only processes that USDA, the National Center for Home Food Preservation and the University of Georgia have to recommend for half-gallon jars are for very acidic fruit juices (and juice only): See more information on their web site here: Apple Juice ( and Grape Juice ( This process time is not to be used for tomato juice, for example.

There are no other research-tested processes for half-gallon jars. Boiling water processes for other foods for jars larger than those published with recipes (usually pints and/or quarts) cannot be extended by any formula to a larger jar.

We are aware that there are historical recommendations for canning foods in half-gallon jars. However, these are not currently accepted or endorsed by the USDA, Cooperative Extension System or U.S. manufacturers of home canning jars.

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