The Basics About Canning Jars

with Sharon Peterson

Canning Jars: Common Questions Answered Here.

Canning jars are pretty straightforward. They’re glass jars that you use in your canner to preserve food, and they come in several sizes.


Different Sizes & Kinds of Canning Jars

Canned goods.

Canning jars come in many different sizes (most commonly pint, quart, and half-gallon). I used quart jars for years, until my children left home. Now I use pint sizes more often, since pints are perfect for serving just a few people, depending on the food that's being canned. (For example, corn fits tighter in jars, so a pint jar of canned corn is plenty.) What size you use depends on how much of the food you’ll eat at a meal.

Other than the gallon-sized jars that are only used for storage, all sizes of jars are used for canning. However, you only use the half-gallon jars for canning juice (apple juice or grape juice). There are no tested recipes for these jars. I think they used to be more commonly used, but there are no recipes out there that are tested as to how long you should process for shelf storage and whether it gets heated through or not. (Half-gallon jars also come in wide- and regular-mouth designs.)

There are also smaller jars, including half-pint and odd-shaped jars, which work well for relishes, jams, and jellies. (I use embossed jars for jams/jellies that I’m giving as gifts.) I hardly can anything in the tiniest jars, except apple butter, since I’m the only one in my house who likes apple butter! You could also can baby food or make wedding favors using smaller jars.

Different Kinds of Mouths 

Different canning jars.

The opening of the canning jar is called the “mouth,” and whether you use wide-mouth or regular-mouth depends on the type of food you’re putting in the jar. It’s a personal choice, as they can be used interchangeably. 

Personally, I use wide-mouth jars when canning meat, because it’s easier to clean wide-mouth jars after removing the food. (Meat leaves a residue inside the jar that dishwashers can’t remove.) I also use wide-mouths for canning peaches. When canning peaches, you’re arranging the peaches cavity-side down, and it’s easier to arrange fruit in wide-mouth jars.

Wide-mouth and regular-mouth canning jars are most common here. I’ve read that in Canada and other places outside of the US, they have jars with narrow mouths that are a little smaller than the regular mouth on a canning jar.

Brands of Canning Jars

Empty canning jars.

Kerr and Ball are both trusted canning jar brands. (Jarden owns both companies.) I also like Orchard Road jars--they seem like heavier glass.

Also, Fillmore Container sent me a case of the Anchor Hocking jars. I really like those jars, too. They actually feel like a heavier glass than Ball or Kerr jars. Now, I haven’t measured them or weighed them to know exactly, but I really like the jars. One thing that’s really nice about Anchor Hocking is that they don't label their jars, so they work great for labeling your own products or gifting jams/jellies. 

The only negative about these jars is that they aren’t “approved” for pressure canning. I went to their website and looked at the description to see what they had to say, because I wasn’t familiar with Anchor Hocking, and I noticed that it specifically said "for water bath." So I contacted Fillmore and asked them, and they said that they can’t recommend them for a pressure canner. Why? I don’t know. They seem like a nice, heavy jar, so that’s the only negative about them.

Debates & Common Questions About Canning Jars

Old canning jars.

“Can you reuse mayonnaise or pickle jars from the store that aren’t ‘canning' jars?”

According to the National Center for Home Food Preservation, you can use recycled jars like old mayonnaise or pickle jars from the store, but you’re better off going with actual canning jars. Don’t use them in a pressure canner, but it’s possible to use them in a water bath, though you can expect a higher failure rate. Because of that, I agree that you’re better off getting canning jars.

"What about using bottles or plastic containers for home canning?"

This question came from Jerry in Minnesota. He said: "My neighbor is planning on canning tomato juice in 2l plastic pop bottles with screw top lids. He plans to seal the lids with clear tape or parafilm-type material wrapped around the screw-on cap. Will the hot tomato juice extract dangerous chemicals from the plastic? Is this a safe possibility?"

My answer? I would definitely NOT consider this to be safe. There are several problems I forsee:

1 - The pop bottles would not survive processing. It could be he is not planning on processing the bottles in a canner. He may be going to simply fill the bottles while the tomato sauce is hot. I have more information on this type of canning here. See Open Kettle Canning.

2 - Tape is not going to last, and I would not trust it to keep the container air tight.

3 - As far as the plastic safety, I don't know what to think about that. I am not an expert on plastics and safety. If they are pop bottles, they are supposedly food safe, but if heated, that may change. I am also not sure it would keep chemicals from seeping through the bottle to the food.

I strongly recommend that your neighbor reconsider.

Here are some thoughts on this from other readers:

Acidic Tomatoes
by: Anonymous

"Not to mention what the acid from the tomatoes would do to the plastic"

NOT SAFE
by: Anonymous

"Think about this, have you ever got an expired bottle of pop? Do you remember how stale/flat it was? The pop expires after 3 months because there is air leakage in the bottle causing the flatness. Any air in is bad in canning."

Yikes!
by: Anonymouslinda warren

"This is a completely stupid idea! And dangerous."

“What about used or vintage canning jars? Can you use them for canning?”

Well, I hardly ever buy new jars. Used jars are perfectly safe for canning! Just be sure to check them first, running your finger over the rim of the jar to ensure they’re not chipped. (Sometimes there will be small chips that could prevent a proper seal.) Also, don’t reuse the lids. Just reuse the jars.

Old canning jars are really nice, too. They’re made of heavy glass and are perfectly usable for canning. When you have the REALLY old jars, however, like the Drey jar I have that has bubbles in the glass, don’t use them for canning. Save very old jars (or jars with wired lids) for storage, not canning.


Question from my inbox:  Keeping Canning Jars Hot

Sharon, I don't usually can only one batch at a time so I have time between the processing of one batch and the next. In that time, my jars get too cool. 

What's the best way to keep them warm enough not to break when they hit the water in the water bath or pressure canner? 

I usually use the dishwasher to sterilize them, but they will still cool off after waiting an hour for a batch to process.

Thanks!

You could do several different things.

What I usually do is just put the jars in the canner that is heating up.  The hot canner heats the jars at the same time.  Take them out fill them and put them back.  If you have a set of jars waiting for the second batch just put them in your canner when you've got the first batch out.  It won't take long for them to heat up.

If you are using the dishwasher just run the rinse cycle for a few minutes before packing the second batch. Just enough to warm the jars. 

Place them in a sink of hot water, of course the water may cool off. Just run fresh hot just before you fill them.

I've seen it recommended that you place your jars waiting in a warm oven. However I've checked into that and jar manufacturers don't recommend any oven heat for their jars. I've been told that the jars may be compromised with a dry heat. I don't recommend this method.

Some more reader suggestions

Reader Suggestion

-  I always have a large extra pot of water on the stove.. I fill it with jars and simmer them until I am ready to use them. Keeps them hot... And I can sterilize them to if need be. One article I read suggested to use a large crock pot filled with water and jars on high heat...


Jar warming 
by: Terri T 

I have struggled with this as well. But one thing that works really well for me is to put the rack of the canner in the up position and put the jars in there. That way I have about 1/2 inch of water that the jars are in to keep warm. If I am doing one batch, I just put them in there as I am warming the water. But if the water is already hot, then I prewarm the jars under hot water. As I fill the jars, I take one out, fill it, put it back into the steamy bath, and take the next jar.



Keeping jars hot
 
by: Dave Wakefield 

I use a roaster oven with about an inch or two of water. Place the jars upside down as shown in the stove top pan example shown above. The roaster oven keeps many more jars warm and doesn't use a burner on the stove. You can also pre-warm your lids in the water also.


Hot jars 
by: Robin Moore 

Ok get a oblong cake pan & place a tea towel in bottom. Put your jars in waterbath canner or deep pot to sterilize. Right before filling remove jars and place hot jars on tea towel. Use a ladle in put 3 ladle dips of hot water in cakepan. My Granny did this. Then fill hot jars & process. Works great as pan & tea towel holds heat.

Why heat canning jars?

hot canning jars?
by: Loretta

"Do the jars need to be hot because they will crack otherwise? Or is it related to safety of the product being canned? If it's the first, then can't you put them in a sink of very, very hot water to prevent that?"

Answer:

Yes, it is because the canning jars may break if very hot food is added to a cool jar. And yes again...you may certainly put them in either a sink or pot of very hot water.

I've even used the jars just room temperature, cautiously added a small amount of my hot food to each jar, and then gone back and filled them. This way the jar slowly raises temperature.

But be very cautious with this. This is my quirky way of filling jars when my burners and dishwasher both are full! :0)

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