Looking for Headspace - Home Canning FAQs: What is Headspace? in 2023? Scroll down this page and follow the links. And if you bring home some fruit or vegetables and want to can, freeze, make jam, salsa or pickles, see this page for simple, reliable, illustrated canning, freezing or preserving directions. There are plenty of other related resources, click on the resources dropdown above. If you are having a hard time finding canning lids, I've used these, and they're a great price & ship in 2 days.
The unfilled space above the food in a jar and below its lid is referred to as headspace. Directions for canning typically specify leaving 1/4-inch for jams and jellies, 1/2-inch for fruits and tomatoes to be processed in boiling water, and from 1- to 11/4-inches in low acid foods to be processed in a Pressure Canner.
This space is needed for expansion of food as jars are processed, and for forming vacuums in cooled jars. The extent of expansion is determined by the air content in the food and by the processing temperature. Air expands greatly when heated to high temperatures; the higher the temperature, the greater the expansion. Foods expand less than air when heated. This is why you must leave more headspace when using a Pressure Canner!
Canning & Preserving for Dummies by Karen Ward
most recent version of
the Ball Blue Book