Some of my canning jars didn't seal
A jar that didn't seal is not a disaster — it's a jar that needs refrigerating. Causes are nearly always mechanical, and all of them are avoidable next batch.
What actually works
Those are the only two options. **Never store an unsealed jar**, and never push the lid down and call it sealed.
A chip or a smear of food on the rim stops a seal. Wrong headspace stops it. **Bands tightened too hard** stop it — fingertip tight only, because air has to escape.
Trapped air expands and breaks the seal, and it's also how jars siphon liquid out during processing.
Don't move them, don't touch the lids, don't put the hot jar on a cold surface. Thermal shock and jostling break more seals than anything in the recipe.
The sealing compound is designed to deform once. Reused lids are a leading cause of failed seals — and bands are reusable, which is where the confusion comes from.
Run the numbers
- Canning altitude adjustment → — free calculator, works offline.
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