Frequently Asked Questions
Search Knowlege Base
Canning -- Miscellaneous
What is headspace? Why is it important?
The space in the jar between the top surface of the food or its liquid and the inside of the lid is called headspace. Leaving the correct depth of headspace is essential to achieve a strong vacuum seal. If jars are overfilled, the contents may siphon or boil out during processing. Any food residue which then may remain on the jar rim, such as grease, juice, seeds or pulp can prevent the formation of an airtight seal. When too much headspace is left, all the air may not vent from the jar during processing, preventing the formation of a strong vacuum seal. The type of food being canned determines the amount of headspace. See Step-by-Step. Source: Original FAQ posted at http://www.homecanning.com/usa/alfaq.asp