Canning Headspace Rules to Follow

October 20, 2023
Blain's Farm & Fleet

Learn about the proper headspace guidelines to follow while canning.

If you are relatively new to home canning, you may not know the importance of headspace in canning.

Canning headspace is the empty room that’s left in the top of your jar after you add the contents and before you put the mason jar lid on.

No matter what you are canning, or if you’re pressure canning or water bath canning, leaving the correct amount of space specified before processing the jar is extremely important.

Leave enough headspace…

The heat applied to a mason jar during processing causes the contents inside the jar to expand. As air escapes around the lid, canning headspace will decrease.

If you did not leave enough canning headspace, the contents of the jar could seep under the lid. And the canning jar may not seal right.

But don’t leave too much headspace!

Leaving too much canning headspace can also be a problem. Cooling jars naturally contract and pull the lid down tight to seal the jar completely.

If there is too much canning headspace, the processing time called for in the recipe may not be long enough to drive out the air in the jar.

More air in the mason jar means more oxygen is present to discolor the food and promote rancidity in fats. This can prevent it from sealing properly.

Determining the right amount

You need canning headspace when food begins to expand during the canning process, and for forming vacuums upon cooling.

Air expands when heated to high temperatures. The higher the temperature, the greater the expansion. Food expands less than air when heated.

Before you begin a canning recipe, be sure it specifies how much canning headspace to leave, as every recipe is different. The best recipes will tell you how much to leave.

Some canners follow the general rule of 1″ for foods like vegetables, 1/2″ for fruits, and 1/4″ for jams and jellies. When canning meats, poultry, and fish, it is best to have a headspace of 1″ to 1-1/4″.

For more more tips and ideas, visit our Canning Blog.