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Canning jars lids and rings are unique, fussy things. Consequently, there are many questions people have about canning jar lids, rings, bands, wires and other fittings. Here is a collection of popular and common questions about canning jars lids, rings and attachments. See this page for questions and answers about the canning jars themselves (rather than the lids / rings). 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.
As my jars are cooling after I take them out of the canner, they sometimes make a popping or hissing noise. Is this normal and safe?
Yes, the lids are designed to flex and that's actually a key selling point. You can tell if a jar hasn't sealed properly (after it has cooled completely) if the lid flexes and makes a popping sound when you press the center of the lid with your finger. The popping sounds while it is cooling is the lid being sucked down by the vacuum that is forming inside the jar - which a normal part of the sealing process. Hissing sounds are usually just escaping steam or hot water evaporating on hot surfaces, also normal!
I followed your instructions for canning blueberries (hot pack). I tightened the jars until they were totally closed, and then set them down (on their side) in a pot to process. I had to process them on their side because I didn't have a large enough pot to do otherwise and didn't want to spend the money on one. I noticed after processing each jar and removing it from the pot of boiling water, that the water would become tinged with purple, indicating that some juice had clearly leaked from the jar. Then, when the jar would cool down, I noticed that I could still tighten the lid (even though I had tightened it as far as it would go before I put it in the pot to process). Is this leaking normal? Is it going to be a problem when I go to eat my canned blueberries?
Yep; there are two things going on. First, don't overtighten the rings, that can cause the lids to deform and leak. Next, don't lay the jars on their sides. When the contents expand in the hot water, the contents will be pushed out, rather than the air! The jars may not even seal properly.
How would you go about using different 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. "
What if the lids on canning jars spring back after canning?
Run for the bomb shelter before they explode! Nah, just kidding, it's not that bad. But unfortunately, it does mean that the jars failed to seal correctly.
Most likely, the lids weren't seated correctly, often due to spilled contents on the rim of the jar or sealing surface of the lid - OR the contents never got hot enough to create sufficient vacuum when the jars cooled OR the lid's glue was cold.
Next time, wipe the top of the jar, use clean new lids, which were kept in barely simmering water and be sure to fil the jars with hot contents and process right away and for the full duration specified in the recipe.
If you do get jars which don't seal properly, you can either put the jars in the refrigerator and use them first, or empty them jars back into a pot, heat them up again, re-jar them, put new lids on and process them again...generally, that's too much work, so unless an entire batch fails, I stick the few that fail to seal in the fridge.
Lids should not be used a second time since the sealing compound becomes indented by the first use, preventing another airtight seal. Screw bands may be reused unless they are badly rusted or the top edge is pried up which would prevent a proper seal.
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.
I've occasionally seen this on my lids, too, but never experienced any illness after eating the contents.
The USDA/University of Georgia National Home Preservation Center says natural compounds in some foods, particularly acids, corrode metal and make a dark deposit on the underside of jar lids. The underside of metal lids is protected by an enamel coating. If there are any imperfections in the enamel, e.g., tiny scratches or pinholes, natural compounds in food can react with the metal in the lid to form brown or black deposits. This deposit on lids of sealed, properly processed canned foods is harmless. In addition to the causes listed above, sometimes bits of the canned food adhere to the lid, and dry there, causing a dark spot.
What causes lids to buckle?
Putting screw bands on so tightly that air can hardly escape from jars during processing. The buildup of pressure inside jars causes lids to buckle. Screw bands should be tightened firmly, by hand. Do not use a jar wrench to tighten screw bands.
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?