My wife and I are about to do some tomato canning tomorrow. We have a bunch of mason jars that we didn't have time to sterilize. She thinks that just washing them in hot water is enough. After searching around all instructions require boiling.

What is the bare minimum necessary?

7 Answers 7


Before filling the jars, you should do the following:

  • Place the jars (right-side-up) on a rack inside a boiling-water canner
  • Fill the canner and jars with water to one inch above the jars
  • Boil for 10 min (or more for higher elevations)
  • Remove and drain the jars, one at a time

I toss the lids and rings in there as well, since the lids seal best when the rubbery-stuff is softened first anyway.

I have read that some people use their dishwasher's "sanitize" cycle instead, but you should contact the manufacturer (or check the user's guide) to see if it really gets hot enough. I don't know much about using the dishwasher for this purpose; perhaps someone else can elaborate.

If you're looking for great canning instructions, check out the National Center for Home Food Preservation. They will explain how to can safely, botulism-death-free.


Washing them in hot water is most certainly not enough. Sterilization via boiling under pressure is guaranteed to kill every harmful pathogen, particularly Clostridium botulinum, the beastie responsible for botulism. The "hot" water from your tap is not enough to kill the spores. C botulinum spores must be heated to 250 F for at least three minutes to guarantee they are killed.

Please do not compromise here under any circumstance. Canning requires sterilization, not sanitization. Botulism can paralyze and kill you.

  • What about the boiling of the jars after we've sealed them with their contents? Is it too late by then?
    – milesmeow
    Sep 4, 2010 at 3:04
  • 2
    @hobodave I think @milesmeow was talking about how to sterilize the jars before filling them, in which case you don't have to put them under pressure, but you do have to boil them. @milesmeow No, it's not enough to boil them only after sealing. Check out the Ball site (freshpreserving.com) or the Nat'l Ctr for Home Food Pres. for more info Sep 4, 2010 at 3:09
  • a textbook of mine mentions 'grave consequences like death'. LMAO. Sep 4, 2010 at 17:46
  • 1
    @Sean After washing with soap, the two easy methods that come to mind are by using your oven (for 30 minutes) and your dishwasher (if it has a sanitize setting that achieves 250 for an extended period of time). I haven't used them, but I have a neighbor who swore by the former until she discovered the latter: I could be wrong
    – mfg
    Feb 2, 2011 at 21:56
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    Oven is dry heat, beware that dry heat typically requires much higher temperatures than wet heat to kill things.
    – derobert
    Apr 7, 2011 at 16:40

All professional sources and manufacturers of canning equipment (Ball, Kerr, etc) now say "If processing for 10min or more, the only sterilization needed is hot soapy water prior to filling, the processing time will finish the job. If processing time called for is less than 10min, then you will need to do a full sterilization which consists of the hot soapy water wash followed by 10min at boiling in the water bath canner prior to filling." This does not include rings and sealing lids, as those have only needed the hot soapy bath for many years now (regardless of processing time or any and all other factors).

Link to the National Center for Home Food Preservation page on pre-sterilizing


You do NOT need to sterilize jars that will be processed in a pressure canner or processed in a boiling-water bath for more than 10 minutes. (Jars that you will process in a boiling-water bath for less than 10 minutes DO need to be sterilized by boiling them for 10 minutes before filling them with product.)

In any case, you need to wash the jars, lids, and rings in hot, soapy water before filling them -- and be sure to rinse them well so that no soap residue remains.


This is just my opinion, but if you're going to go to the trouble of canning in the first place, it seems worth it to properly sterilize the jars so that the food you're putting up will last. The boiling step is the easiest part of canning, really, and it doesn't hurt to do it. It would be terrible to spend the afternoon canning, skip the sterilizing part, and then have all your work be for naught if the stuff goes bad quickly later.


I have seen sources claiming that presterlization is not needed for tomatoes.

  • 1
    It really depends on the amount of time the jars spend processing. And that link firstly doesn't work anymore and secondly is about pressure canning, which is a lot different from hot water canning.
    – lemontwist
    Oct 21, 2012 at 12:53

I always use freshly scrubbed jars, dip them in boiling water for 1 minute, then can using the water bath 10 minutes+. I don't want to take a chance and it only takes a minute. I seriously doubt if my jars are well cleaned, stored dry for a year that there will be much bacteria if any. I don't live in a 3rd world country...

  • 2
    First, it doesn't matter if you live in a third world country, bacteria are everywhere. First world country food chains may be even more contaminated due to mass animal husbandry. Second, what you describe is how you personally like to do it, but you are not giving any reason why this sterilization procedure is either sufficient or minimal.
    – rumtscho
    Sep 7, 2015 at 8:08

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