What jars are suitable for home canning?
Use jars made for home canning, which are built to take the heat and pressure of canning. Jars from commercial products such as store-bought sauces and pickles are not designed for repeated canning and may break or fail to seal properly. Ask your extension office what they advise.
Jars are sold in different shapes and sizes, and tested recipes specify which can be used. Follow the recipe's jar guidance and never substitute from memory. Old jars passed down in families can be lovely and still not be right for canning. Many are made of thinner glass, have different threads or sit awkwardly with modern lids. Ask your extension office whether a particular antique jar is appropriate before using it, and keep it for dry storage or display if there is any doubt.
How do you inspect jars before use?
Run a finger carefully around the rim, and look at the glass in good light. Check for chips, cracks, nicks, scratches and rough spots, especially on the rim, where the seal forms. Discard any damaged jar or keep it for dry storage only.
Check for cloudy buildup or mineral film. Wash such jars and see if the film comes off, which is often a hard water problem. Sort jars by size before canning day, so you can find the right ones quickly, and set aside any with doubtful rims right away instead of finding them mid-batch.
- Look for chips and cracks, especially on the rim
- Discard damaged jars from canning use
- Wash off mineral film if present
- Keep jars clean until you are ready to fill
How do you wash and prepare jars?
Wash jars in hot soapy water and rinse well, or use a dishwasher. Your tested recipe will tell you whether jars need to be kept hot or sterilized for the particular food and process. Follow it for that detail.
Handle hot jars with a jar lifter and set them on a towel or rack rather than a cold, wet surface, to avoid thermal shock that can crack glass.
How should you treat two-piece lids?
Most home canning uses a flat lid with a sealing compound and a separate screw band. The flat lid is made for one use. Do not reuse it for canning, since the sealing compound may not form a reliable seal a second time. Bands can be reused if they are clean, straight and not rusty.
Follow the lid maker's instructions on preparing lids, because the guidance has changed over time. Check the current instructions printed on the box or on the maker's website. Keep a supply of new flat lids on hand before canning day, since running out in the middle of a batch leads to shortcuts. Store unused lids in a cool, dry place, and check the maker's guidance on how long unused lids stay good, because the sealing compound can age.
How do you check seals after canning?
After processing and cooling, follow your tested source for how to check seals. A sealed lid is concave and does not flex when pressed. Label and store sealed jars. If a jar did not seal, ask your tested source whether to reprocess with a new lid or refrigerate and use it soon.
Remove bands for storage if your source advises it, so a false seal cannot hide behind a tight band.
How should you store jars?
Wipe jars clean, label with contents and date, and store in a cool, dry, dark place. Avoid stacking jars in a way that puts weight on the lids. Keep them off floors that may flood.
Empty jars can be stored upside down or with lids loosely placed to keep dust out. If you move jars to a new shelf or carry them in boxes, pad them well so that they do not knock together. A hairline crack from a bump can show up later as a leak. Keep spare jars in a sturdy box with dividers, and write the size on the outside, so that you can find what you need quickly at the start of the season. Check the box for damage every year.
When should you discard a jar of food?
Discard food from jars with leaks, bulging lids, spurting liquid, mold, cloudiness, bad odor or any sign of spoilage. Do not taste it. Dispose of it where people and animals cannot reach it, and clean surfaces it touched. Ask your extension office if you are unsure what to do with a suspect jar.
Key takeaways
- Use jars made for canning and inspect every rim for damage.
- Flat lids are single-use; bands can be reused if clean and straight.
- Follow your tested source for preparing jars and checking seals.
- Discard any jar showing leaks, bulging, mold or odor without tasting.
Sources and further reading
Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.