Are mason jars safe to use for hot soups?
Yes, with thermal-shock care. Warm the jar first, and do not pour boiling soup into a cold jar.
What's actually in it
Mason jars are glass. For food contact, that is a better choice than putting hot soup in plastic. The safety issue is physical breakage, not plastic additives.
A cold jar plus very hot soup can crack. A room-temperature jar is better. A jar warmed with hot tap water first is better still.
What the research says
An FDA inspection guide for low-acid canned foods warns that glass jars can break from thermal shock when the jar and water temperatures are too far apart.
A 2025 study in J Agric Food Chem found polypropylene food containers released nanoplastics and microplastics into water, with higher release after 90 degrees C rinsing than room-temperature rinsing. That supports choosing glass over hot plastic when you can do it without breaking the jar.
For soup, preheat the jar with hot tap water, pour the water out, then add hot soup. Leave headspace at the top. Do not tighten the lid while steam is still building pressure.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Guide to Inspections of Low Acid Canned Food 28 | FDA | |
| Release of Nanoplastics from Polypropylene Food Containers into Hot and Cold Water. | J Agric Food Chem | 2025 |