Is it safe to pour boiling water into a glass jar?
Only if the glass is made for heat and warmed first. Thin reused jars can crack.
What's actually in it
Glass is a good food-contact material for hot water. The danger is thermal shock: a sudden temperature change that cracks the jar.
Heat-rated glass handles this better than thin reused jars. A cold jar from the fridge is the wrong place to pour boiling water.
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 is the reason glass is worth using for hot water when the jar is heat-ready.
Use heat-rated glass for boiling water. Warm the jar with hot tap water first. Save thin pickle jars and cold jars for room-temperature or cold storage.
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 |