Why are your canning jars cracking when the hot food are placed in them?

Answer 1

The most common reason for jar breakage is thermal shock. Either you are putting cold food into hot jars, or hot food into cold jars, or cold jars into boiling water.

To prevent jars breaking when putting them into a water bath, begin by washing your jars in hot water. If the water in your sink is not too hot for your hands, it will not shock the jars. After rinsing, put them immediately into the water bath and fill it over the top of the jars with hot tap water. Bring the jars to a boil and let them remain there for 15 to 20 minutes. Afterward, turn off the heat, and let the jars remain in the water bath until you are ready to fill them. Fill hot jars with hot food. lid and ring the jars and return them immediately tot he water bath (if you are hot bath canning--if you are pressure canning, put the jars into the pressure canner rack and fill the canner with hot water after the jars are all in place. (DO NOT PUT COLD WATER OVER HOT FILLED JARS).

Answer 2

Glass cracks when internal stresses is exacerbated by thermal shock.

Mason jars are made of tempered glass, which is to say glass that has been heated and allowed to cool, to relieve those stresses. Mayonnaise jars are made of cheap glass.

It makes sense to use Mason jars in home canning, because you can wash those mason jars and reuse them for the next harvest, year after year for half a century or more. Home canners pay premium prices for the peaches and tomatoes they can.

Commercial canners buy produce for less than 10% of retail prices, so it's not such a loss when a jar cracks - and because they can't reuse jars, they can't amortize the higher cost of real Mason jars. They also use industrial steam to process canned goods, and use glass that is only days old, both of which reduce the number of failures.

You can reduce your failures by preheating your mayo jars to precisely the same temperature as the food you're canning, but it's still a bad bet. It's generally much more economic to use real Mason jars. (Mason was originally a brand name, but most Mason jars over the past decades have been made by Ball or Kerr. If it's a Mason jar, it will say it's a Mason jar.)

You'll also want to inspect your Mason jars before using them. Chips, especially in the mouth or the threads, can lead to the can failing. Such jars are usually safe for refrigerator storage of leftovers, but inappropriate for freezing or canning.

The lid, ring, food and jar should all be heated to the same temperature. Wipe the mouth of the jar clean before putting on the lid and screwing down the cap. Once the cap goes "Bing!", signalling that it's concave, the ring should be loosened, and before the jar is placed in the pantry, the ring should be entirely removed and stored.

Very few people bother with home canning any more. It's easy, economical, and what's more important, it allows us to eat better than we otherwise could. It's probably rude to gloat publicly that you're better than most people - but simply knowing it should give you a warm feeling.

Answer 3

When canning, a minimum of water is kept in the jar for several reasons. First, the less water you have, the more you can fit the canned food. Dried tomatoes consume less space than the same number of fresh tomatoes. Second, water is a breeding ground for bacteria and other organisms that can spoil your food. The less water you have in the jar, the more difficult it is for these organisms to thrive and spoil your food.

Answer 4

Two possible reasons for jar breakage when you place them into the boiling water:

1. The jars are old and need to be replaced.

2. The jars may need to be preheated by placing them in hot water, then filling them with hot food before immersing in the boiling water. Quick changes in temperature such as from hot to cold or from cold to hot can cause glass breakage.

Answer 5

First guess would be going from room temp to hot water or some other drastic change in temperature?