Canners: Oven Sterilizing/sealing a good idea?

A canning rack is preferable to a towel in the bottom of the canner because towels don't allow water to circulate around the entire jar the way a rack does. You can use upside-down jar lid bands in lieu of a rack if you have a collection of old ones that have gotten dinged or slightly rusty (and what canner doesn't?).

you can also put aa old clean towel in the bottom of the canner to keep things from rolling around. You can also do this if you are using a hot water bath for custards or other things in small ramekins or cups.

Just a thought. My small jars bounce around too. I place a rolled up piece of aluminum foil in the water bath to fill up the gaps. Works beautifully.

Thank you, ChefOno, for your clear and cogent explanation. I learn something every time you weigh in on the science behind a method!

The reasoning / science behind abandoning oven canning is manifold:

As suggested, actual oven temperatures can vary considerably from the set point, both due to inaccuracy of their thermostats and from the way they function. Ovens cycle on and off to regulate temperature and there can be a considerable variation between the temperature at which they turn on and when they turn off. The set point can represent the high, low or average temperature -- or none of the above in many cases. In contrast, water boils at a consistent point with simple, known adjustments for altitude.

Transmission of heat through air is inefficient compared to water or steam. Put your hand in a 250F oven and then put it in boiling water if you want a quick demonstration of the principle. So a 250F oven will not heat food to the same temperature as a boiling water bath unless it were to remain for a considerably longer time. And even then it wouldn't if the surface of the food is left exposed due to heat lost through evaporation. Canning requires known times and temperatures to be safe.

Radiated heat from direct exposure to an oven's heating coils has shattered many a jar causing injury, loss of food and one hell of a mess. Blue Chair's desire to return to a simpler time may give some people a warm and fuzzy feeling but could very well produce fuzzy food and a case of botulism in the process.

Don't sacrifice all that work by using a method that sounds questionable to so many of us , and to me, sounds like more work than water bath canning.

When I have a canning question, I go to the Ball site and click on "safe canning procedures". I also add a link there when I do a post on my site that involves canning. This is a better idea than to just say "Process according to safe canning procedures". That oven method is NOT recommended, by the way.

I'd be interested in some scientific evidence one way or another. I would think canning jars placed in a 225 degree oven should heat the food as much as in a 212 degree boiling water bath, but maybe I'm missing something. Oven temps are notoriously inaccurate and unstable, so one concern is that a 225 degree oven will result in temps at the jars that may sometimes be lower than the boiling point.

I do use the Blue Chair method for jams. I love the book.

I just canned some tomatoes today, using the traditional boilingwater method. I do always use the oven to sterilize the jars.

Thanks for the reassurance! I'll stick with the water bath--preserved foods would be a shame to lose to spoilage...sort of defeats the whole purpose. (The canning rack is too big for the little jars so it's a lot of fumbling around. Works great for 7 quarts...I just need to make that next purchase of a small-jar rack)

In agreement with ChefOno. I have been canning, dehydrating and preserving for years and learned from my grandmother and mother as well as taking classes. Don't know why the author of the book would make the recommendations she did. Real research has been done by universities and state schools, along with Ball. So follow the directions of the manufacturers and the excellent link Ono provided.

Don't know what problems you are having with your canning rack. I have two sizes of canners, one for quarts and the other for pints and half-pints. Maybe your rack is too big for your jars?

Don't do it.

http://nchfp.uga.edu/how/general/equp_methods_not_recommended.html