Canning Jars and Lids—An Update

Mason Canning Jars

Mason glass jars are designed to be reused. Canning jars have a life expectancy of 10 to 13 years. You will discover more breakage after that because of the wear and tear of normal use. Each time a jar is used and exposed to heat it is subject to stress. Over time this stress may create hairpin cracks that will weaken the glass. Jars that are handled carefully may still be in good condition and suitable for canning beyond 10 years.

Recently an Extension Educator was asked about using old jars from the 1920’s to 1970’s.  Jars from the earlier period should be considered antiques and used only for decorative purposes. Use them as vases or canisters.  The tinted ones add a pretty touch of color in a room. Jars with wire bales or rubber rings used with glass or zinc lids should be used for storage only.

Jars from the mid-century often have a flat rim with rougher edges that sometimes cuts through the sealing compound of the lid.

The glass in newer jars appears to be thinner, but it has been tempered and is stronger.

Use caution when buying used jars. In the long run, it is often more economical to purchase new jars because you are risking less cracking of jars during processing and loss of product.

Realizing the difficulty of buying new jars this year, you may end up using older jars from garage sales or handed down through the family. Examine the jars carefully for any nicks, cracks, or hairline stress. Examine the sealing edge for smoothness.

We are seeing a number of new brands of jars on store shelves.  Many are imported, and we do not have any information about the quality of those jars.

Colored Glass

You may find colored jars—blue, green, and purple—made for home food preservation; the colored glass may distort the appearance of the food in the jar. Other colored jars such as yellow ones are designed for craft projects. In fact, look at box labels to determine that the jars are suitable for canning. Some clear jars are made for craft purposes and not suitable for canning. Some will have a warning “not for canning" molded into the glass.

Decorative jars

Ball released newly designed jars in a spiral shape in 16 and 28-ounce sizes and a Sharing Mason Jar (6 sided) available in a 16-ounce size. This year they introduced a stackable jar. Some popular European Jars also come in different sizes and shapes. Tulip-shaped jars are not recommended because the wider part of the jar will not heat at the same rate as the more narrow part.

Sizes of Jars

Directions for heat processing are based on the size of the jar.

• Most fruit and vegetable directions include times and pressures for pint and quart jars.
• Jellies usually give directions for half-pint jars.
• If you have a jar that is between sizes, use the time and pressure for the next larger size.  For example, if you have a 24-ounce (3 cup) jar, use the process time for a quart jar, or if you are processing jelly in a 4-ounce jar, use the process time for the half-pint jar (8 oz.).
• Half-gallon jars are too large to allow adequate heat transfer to the center of the jar and should only be used for canning highly acidic apple or grape juice.
• One-gallon jars are not recommended for food preservation.

Commercial Jars a.k.a. One Use Jars

Do not reuse commercial jars. They are intended for one use only. There will be greater seal failures and jar breakage because the glass is not well-tempered. Recent pint and quart mayonnaise and salad dressing jars have a slightly smaller neck and the standard ring band may not securely fasten the lid. In fact, many of these jars are now plastic and not suitable for canning.

Relevant Information about Canning Lids

At the time that this article is being written, canning lids are not to be found on store shelves. Hopefully by May or June, you will be able to purchase the supplies you will need for canning.

Keep in mind some basic facts about canning lids. 

• The standard canning lid is a two-piece lid consisting of a flat metal disk and a screw band. 
• The bands are reusable unless they are rusty, bent, or dented. 
• Use a new metal disk each time. Using the metal disk more than one time risks seal failure. The sealing compound on the lid is only guaranteed to seal once.  When the sealant is heated during processing, it softens and takes the shape of the rim of the jar forming a vacuum seal as the jar cools. An indentation forms in the sealing compound. The thinness of this indentation increases the likelihood of inadequate compound to flow over the glass rim on the jar if you attempt to reuse it.
• When sealed lids are removed from jars the first time, the lid is often bent slightly preventing a proper fit on the jar. Use new lids each time.

A number of off-brand lids were marketed last fall. Some of these may create a vacuum seal. However, anecdotal reports from home canners tell us that many of these have higher rates of seal failure. If you choose to use them, follow the manufacturer's directions for preparing and using the lids. It would be good to check the lids for quality (or lack of quality) signs. Is the sealing compound uniformly applied? Is the metal disk symmetrical and the metal evenly coated? 

Consumers have reported buying what they thought was a major brand of lid online, only to discover they were counterfeit. Minor changes to the labeling of the box and print on the lid itself alerted the brand name manufacturer to the problem. Unfortunately, consumers ended up with lids that did not seal.

Reusable Lids

Reusable three-piece lids consist of a plastic or glass disk with a rubber or silicone gasket to create the vacuum seal. Preparation of the lids and gaskets as well as fastening of the lids on the jar will vary by the lid type and the manufacturer. It is necessary to handle the disk to apply the gasket before it is applied to the jar—a process that increases the opportunity to introduce bacteria from your hands onto the lid. Directions instruct you to loosely apply the lid to allow for venting during processing. After processing, you are instructed to tighten the screw band until the jar seals and cools. The disk is solid and you are not able to see if the jar is sealed until you remove the screw band from the cooled jar.  Like regular two piece lids, you must remove screw bands for storage. That is especially important in order to see if the jar is sealed.  Lift the disk gently from the gasket to see if it separates to determine that the lid is sealed. Be aware that reusable lids are more expensive than two-piece lids.  However, the gasket seals can be reused as long as they are not damaged or stretched out of shape and the plastic or glass disks can be reused indefinitely. They can be used for pressure canning as long as the temperature inside the canner does not exceed 250°F.

Avoid Commercial Use Lids

Avoid the use of one piece lids designed for commercial use. Do not reuse twist-off lids that come on pickle jars, spaghetti sauce jars, or others. Bail lids with a rubber gasket are designed for decorative use or dry food storage. There are some lids developed only for storage after the jar is opened, do not confuse these with canning lids.

Use Correct Canning Procedures

If you have a limited supply of lids, use correct canning procedures to make sure that jars seal properly. Refer to Let's Preserve: The Basics of Home Canning to ensure you are using procedures to increase the likelihood of jars sealing. Remember to allow proper headspace, remove air bubbles, clean the rim of the jar, turn the band finger-tip tight, and process high acid foods in a water bath or atmospheric steam and low acid foods in a pressure canner.

Alternatives to Canning

If you cannot obtain canning supplies, you may need to explore alternatives to canning. Most canned recipes will freeze well including vegetables, tomatoes, salsas, and pie fillings. Using specific directions for freezing fruit, especially fruit in a sugar syrup, yields satisfactory results and a fresh fruit taste.  Dehydrating is another option. Dehydrated vegetables can be reconstituted for soups, stews, and casseroles.  Dehydrated fruits make great snacks and can be used to make tasty desserts or served plain as stewed fruit. For a fun treat try Strawberry Fruit Roll-Ups!