Important First Step: Safely Sterilizing Jars For Preserves

Home canning has been practiced for generations since it’s a great way to preserve the harvest from your garden or take advantage of the bounty of in-season produce from your local markets. It may be time consuming to do, but very rewarding and it’s fun to experiment with new recipes.

CollectionOne of the most important things for beginners to know is how to sterilize the jars properly. This is a necessary step since it helps prevent the growth of bacteria or botulism.

As you can see from the instructions below, it’s really not all that complicated to do. What you need is a big pot, a rack that will fit in the bottom of the pot, some boiling water and a bit of time.

How To Sterilize Canning Jars:

  • The night before you are ready to process the food, pick through the jars one-by-one, checking for any cracks or chips inside and out as well as along the rims. If you do find flaws, set these aside to use for other projects (they are more susceptible to breakage during the packing process or allow bacteria to thrive after they have been sealed).
  • Wash them thoroughly in hot soapy water and rinse well to remove all traces of detergent.
  • Set each empty jar right side up on a rack placed in the bottom of a water canner or large kettle and space them about 1″ away from each other and 1″ from the sides of the kettle. Fill both the empty jars and the kettle with hot water until the water level is at least 1″-2″ above the tops. Cover kettle with lid.
  • Bring water to a boil and then continue boiling for 10 minutes (Important: start the timer only once the water starts to boil). For those who live in areas that are at higher altitudes than 1,000 feet, the time necessary will be longer–typically 1 minute extra per additional 1,000 feet.
  • Once the 10 minutes is up, turn off the heat and allow them to sit in the hot water until they’re ready to be packed (keep lid on). When ready to use, drain the water from each jar as needed being careful not to touch the rim or inside with anything that hasn’t been sterilized first. Make sure to fill quickly after draining to prevent contamination from airborne bacteria or mold spores.
  • Don’t forget to also process the lids, screw caps and rings as noted by the manufacturer.

Good to Know:

  • The reason why you fill the empty pot & jars with hot water and not boiling is to prevent the glass from shattering from the sudden contact with intense heat. Hot water is fine (will help get to a boil quicker).
  • Can you reuse empty jars from commercial products (say you’ve finished off your favorite brand of pickled asparagus)? No you really shouldn’t. They are typically a thinner glass (higher risk of breakage during processing) and have rims that don’t fit standard canning lids properly. You’re better off to keep those aside for other non-food projects.
  • Can they be sterilized in the dishwasher? They can be washed in the dishwasher, but no this doesn’t sterilize them. The glass needs to be in boiling water for at least 10 minutes.
  • If I’m processing food for longer than 10 minutes, do I still need to sterilize the jars beforehand? According to the National Center for Home Food Preservation, the answer is no. A processing time of longer than 10 minutes will sterilize the jars. See this page for details: NCHFP.


  • Only use jars specifically manufactured to use in canning, others may not have thick enough glass or be able to bear the heat generated from the process or from the heat of product filled inside.
  • If you find old canning jars for a bargain price at garage sales, don’t hesitate to buy them. They can be used over and over again, just make sure to have an eagle eye and look for chips or flaws in the glass as noted above in the first step.
  • Once empty, cleaned and being packed away for storage until the next harvest, sprinkling a little borax or baking soda in them will help keep the jars sweet and fresh until needed again.

Related Posts


    • Pete

    It is worth noting that while many of us still have the old habit of sterilizing our canning jars it is not necessary if your canned products is given a boiling water bath for 10 minutes or longer, or your canning is done in a pressure canner. Obviously the jars still need to be clean, and heated to prevent shocking of the glass when the hot product is added, but for many of us it is easier and more frugal to simply heat the jars in an oven prior to filling.

    For complete recommendations on canning and the proper care of canning jars (and much, much more) see the official info here:

    • Hazel

    I agree with the oven sterilization: I’ve been doing it for years and never had a mishap. I set the oven temperature to 220F (212F is the boiling point of water) and carefully wait for at least 10 minutes at this temprature. Glass does become more fragile with heat, so I am very carefuly to handle with large oven-mitts to protect both the glass and myself.

    • April

    i boiled my jars befor pickling and after pickling a day or two later i noticed a thin milky film on the bottom inside of the jars. what is this,is it harmful and should i throw out the pickles?

    • Beth

    April, it may be that you didn’t use pickling salt? If you don’t, the iodization from the salt will cause a film. It’s not harmful.

Leave a Reply

Your email address will not be published. Required fields are marked *