HOME CANNING · JAR PREPARATION
Clean jars are always required. Pre-sterilizing empty jars is required only for certain short boiling-water processes; many recipes sterilize jars during processing.
When pre-sterilization is required
Pre-sterilize empty jars for jams, jellies, and pickled products processed for less than 10 minutes at elevations below 1,000 feet. Apply the tested recipe’s altitude adjustment; the equivalent sterilizing process increases as elevation rises.
When it is not required
- Empty jars used for pressure-canned vegetables, meats, poultry, seafood, and other foods do not need separate pre-sterilization.
- Jars for fruits, tomatoes, pickled foods, or fermented foods processed for 10 minutes or longer at 0–1,000 feet do not need separate pre-sterilization.
- Jars still must be washed, rinsed, inspected, and kept at the temperature required by the process.
The boiling-water method
- Place clean jars upright on a rack in a boiling-water canner.
- Fill the jars and canner with hot—not boiling—water to 1 inch above the jar tops.
- Boil 10 minutes at elevations below 1,000 feet.
- At higher elevations, add 1 minute for each additional 1,000 feet.
- Keep jars hot and remove them one at a time, draining the water back into the canner immediately before filling.
What does not sterilize jars
A dishwasher cycle, hot tap water, oven heating, or simply pouring boiling water into a jar is not the NCHFP sterilization process. Dishwashers are useful for cleaning and holding jars warm when the appliance and recipe support that use.
Follow the recipe, not a blanket habit
Do not shorten a tested process because jars were pre-sterilized. If a tested recipe offers a longer processing option that removes the need for separate sterilization, follow that option and its altitude adjustment exactly.
Sources and further reading
Use a tested process
Use a current tested recipe from NCHFP, USDA, or a university Extension source. Follow its jar size, headspace, preparation method, process, time, pressure, and altitude adjustment exactly.