Sterilize 16 oz wide mouth canning jars only when the recipe’s boiling-water process runs under 10 minutes; at 10 minutes or more, or in a pressure canner, the processing itself sterilizes the jars.
Which foods you’re putting up decides everything here, not jar size. A batch of quick-pickled jalapeños processed for 5 minutes needs jars straight from a boiling pot; quart after quart of pressure-canned green beans needs nothing more than jars washed in hot, soapy water and kept warm. Get this one call right and you avoid a pointless extra step — or a real safety gap.
Either way, start with clean jars. Wash them in hot, soapy water, rinse well, and set them right side up on a rack while you work. Sanitizing happens after that, and only for some recipes.
When Do Canning Jars Actually Need Sterilizing?
The National Center for Home Food Preservation draws the line at 10 minutes: pre-sterilize empty jars only when the recipe’s boiling-water process time is less than 10 minutes. Foods processed in a boiling-water canner for 10 minutes or more, and anything run through a pressure canner, don’t need it — the heat of processing does the job instead.
That’s why pressure-canned vegetables, meats, and fruits skip the step entirely, per NCHFP. The reasoning is simple: once a jar and its contents sit in a canner long enough, nothing survives.
Jar size doesn’t move the needle. Sixteen-ounce wide-mouth jars are standard Mason-style jars, and the official directions apply to empty canning jars generally. Mouth style and volume change what you pack, not how you sanitize.
How To Sterilize Wide Mouth Jars In A Boiling-Water Canner
Put washed jars right side up on the rack of a boiling-water canner, then fill the canner and the jars with hot — not boiling — water to 1 inch above the tops of the jars. Bring it to a rolling boil and boil for 10 minutes at elevations below 1,000 feet.
Higher up, add 1 minute for every additional 1,000 feet of elevation. Denver-area canners, for example, are looking at roughly 15 minutes.
- Set washed jars right side up on the canner rack.
- Add hot water to 1 inch above the jar tops.
- Bring to a full boil — start counting only now.
- Boil 10 minutes below 1,000 ft, adding 1 minute per 1,000 ft of elevation.
- Pull jars out one at a time, drain them, and keep them hot until you fill them.
Don’t dump the water — it’s already hot and ready for processing your filled jars. And don’t let sterilized jars cool on the counter; cold jars plus hot brine is a recipe for thermal shock.
If you’re still shopping for jars, it’s worth comparing the best 16 oz wide mouth canning jars before you commit to a case, since wall thickness and lid fit vary between brands.
Steam Canner And Altitude Adjustments
An atmospheric steam canner can sterilize jars too, but only with pure steam. UC ANR guidance calls for heating jars in steam at 212°F at sea level — verified with a calibrated thermometer — for 10 minutes at 0–1,000 feet, plus the same altitude adjustment.
That thermometer detail isn’t decoration. A steam canner that’s venting air instead of pure steam hasn’t reached the temperature the method depends on.
| Method | Time At 0–1,000 Ft | When It’s Needed |
|---|---|---|
| Boiling-water canner | 10 minutes, full boil | Process times under 10 minutes |
| Atmospheric steam canner | 10 minutes at 212°F | Process times under 10 minutes |
| Pressure canner | Not applicable | Never — processing sterilizes |
| Boiling-water, 10+ minutes | Not applicable | Never — processing sterilizes |
The NCHFP sterilization of empty jars page is the one to bookmark — it’s the source the extension services themselves point back to.
Mistakes That Undo The Whole Step
Starting the clock before the water hits a full boil is the most common error. Ten minutes means ten minutes of actual boiling, not ten minutes of warming up.
Two more to watch:
- Sterilizing jars that don’t need it. Extra handling means extra chances to touch the inside of a clean jar or chip a rim.
- Wrong water level. Jars need about 1 inch of water above their tops, no more and no less.
One thing this step doesn’t cover: lids. Jar sterilization and lid preparation are separate jobs, so follow your recipe’s instructions for those.
Michigan State University Extension’s guidance on canning jars and safety is a solid second read if you want the jar-handling side in more detail.
Bottom line: check your recipe’s process time and your canner type before you fill a single jar. Under 10 minutes in a boiling-water or steam canner, sterilize. Ten minutes or more, or pressure canning, just wash and keep warm.
FAQs
Does jar size change the sterilizing time?
No. The 10-minute boiling-water figure applies to empty canning jars generally, whether they hold 8 ounces or 32. What varies with jar size is the processing time for the filled jars, which your tested recipe will state.
Can I sterilize jars in the dishwasher?
Dishwasher cycles rarely hold the water at a full boil for a sustained period, so they can’t be relied on for true sterilization. Wash jars there if it’s convenient, then use the boiling-water method if your recipe calls for sterilized jars.
What happens if I sterilize jars I didn’t need to?
Nothing breaks, but you add handling time and risk. More touches mean more chances to knock a rim or leave a fingerprint inside a clean jar. For pressure canning and long boiling-water recipes, washed, hot jars are enough.
References & Sources
- National Center for Home Food Preservation. “Sterilization of Empty Jars” The 10-minute threshold and the boiling-water canner method.
- UC Agriculture and Natural Resources. “Preserve It: Canning Basics — Sterilizing Jars” Steam canner temperatures and altitude adjustment.
- Michigan State University Extension. “Canning jars and safety” Jar handling and safety guidance.
