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Canning in The Oven

In Italian Two Easy, Rose Gray has a recipe for simple tomato sauce. As a footnote, she recommends sealing the jars and putting them in a water bath in the oven at 400 F for 20 minutes. I was very intrigued by this technique and tried it today. So far, only one of the seals is set. I'm wondering if anyone is familiar with this way of canning. I also read on-line someone burning their face and neck because of an exploding jar during a canning session and got freaked out. Did I put myself at risk by trying this method?

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  1. That seems crazy to me. You're supposed to submerge the jars in boiling water.

    1. >>>
      Did I put myself at risk by trying this method?
      In a word, YES! Unless all the sauce you made has not been refrigerated it should be discarded.

      If the sauce only has tomatoes and has added acid, a boiling water bath should be fine. If it has other added ingredients (onions and peppers, for instance) the sauce MUST be processed in a pressure canner.

      If it was refrigerated you can rescue it by putting it all in a kettle and boiling it for 10 minutes, putting it in freshly sterilized jars, sealed with NEW lids, and processing the jars in a boiling water bath...Pints 35 minutes, Quarts 40 minutes.

      The only two USDA approved methods of canning tomatoes are boiling water bath or pressure canning. The purpose of processing is to thoroughly heat the contents of all the jars completely through to kill any nasty microbes, especially botulism. In the oven the water isn't kept boiling, so the temperature is not maintained. This puts the food at risk of underprocessing...a risk I am not willing to take.

      As for the exploding jars you read about, this can happen if you don't use jars designed for home canning. Even tho some pasta sauce jars look like canning jars, they are not the same as home canning jars and shouldn't be used.

      The two best books on canning I have found are Ball Complete Book of Home Preserving
      and Putting Food By

      Home canning can be very rewarding, but it must be done correctly or you or your loved ones could wake up dead.

      I have mentioned this in other canning threads, but it bears repeating. I am not a go-by-the-book person, but when it comes to canning I have religiously gone by the book for over 25 years. I suggest you do to.

      1. I haven't tried it, and won't. It does seem slightly higher risk if a jar breaks - when a jar goes in the water bath canner, I can't even tell till I take the lid off. And I doubt the temperature is as even if you're not totally submerging the jars.

        More importantly, I've water bathed enough custards and such that I KNOW water in the oven is dangerous - pull out a rack with boiling hot water on it and see. No, wait, DON'T.

        Why on earth not just invest in a cheap pot and a jar lifter and do it the right way? You can do tomatoes in a water bath canner. And you won't have to worry about making people sick.

        1 Reply
        1. re: Vetter

          To me, the main issue is not that the temperature would be inconsistent but that the lids are designed to seal at the temperature of boiling water, 220 degrees.

        2. A reliable online source for home preserving is the National Center for Home Food Preservation


            1. I have been canning my whole life (50+ years) and would never try this. Stick with the Blue Book and you won't go wrong. It isn't worth a hospital trip for burns or digestive upset.
              Now, I will say, I do MAKE my ketchup in the oven, since it can stay in there and get nice & thick--THEN when it is finished, I hot pack in hot jars and seal in the water bath canner.

              2 Replies
              1. re: dberg1313

                That sounds like a smart way to make ketchup. Care to share your recipe / techniques? :)

                1. re: rebeccakinney

                  I just put together the ketchup in the ordinary way, using the tomatoes (I used Romas this year) and spices (this was a recipe I got from my friend but I can provide it if you need one). I put the mixture in my large roasting pan--I find a shallow pan works better, obviously because it speeds up the reduction. Put in a 300 oven and watch it, stirring about every 20 min. or so, until you reach your desired consistency. Pour hot, into hot jars, and process the recommended time for your size jars. I tend to use pint or even half-pints for ketchup (who needs it in quart size?! maybe somebody does!). It might be possible to use two pans in the oven at one time, but I only have one roasting pan so it takes two batches. Oh, and of course I remove the rack from the roaster! Anyway this works for me as it avoids the need to stand over the bubbling pot in August. In the oven, it just needs a little watching.

              2. I don't see it working - a water bath would only immerse the bottom part of the jars so they'd heat very unevenly. If you used more water, that's an awfully dangerous amount of boiling water to be pulling out of the oven (not to mention that it would take far longer than 20 minutes to heat up to boiling point!) I scalded myself once badly pulling a boiling pan of liquid out the oven (a roast with broth) - the liquid slops around however careful you are, and your arms and front are right in the line of fire.

                The only canning thing I've used the oven for is sterilising my empty glass jars (so that I didn't HAVE to mess with boiling water.)