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General Canning Information

Equipment and Methods Not Recommended

Open-kettle canning and the processing of freshly filled jars in conventional ovens, microwave ovens, and dishwashers are not recommended, because these practices do not prevent all risks of spoilage. Steam canners are not currently recommended because processing times for use with current models are still being researched. It is not recommended that pressure processes in excess of 15 PSI be applied when using new pressure canning equipment. So-called canning powders are useless as preservatives and do not replace the need for proper heat processing. Jars with wire bails and glass caps make attractive antiques or storage containers for dry food ingredients but are not recommended for use in canning. Neither one-piece zinc porcelain-lined caps nor zinc caps that use flat rubber rings for sealing jars are recommended any longer.

The language above is from the USDA "Complete Guide to Home Canning" (2015 revision).  You may also want to read our National Center Burning Issue: Using Atmospheric Steam Canners. The National Center collaborated with the University of Wisconsin to have research conducted on appropriate use of atmospheric steam canners. As long as certain critical controls can be maintained at various steps in the canning process, there are many products appropriate for canning in atmospheric steam canners. See the Burning Issue above for more information and a link to the University of Wisconsin directions. It will take some time to integrate advice into the USDA "Complete Guide to Home Canning" or other publications and our own website resources.

This document was adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA (Revised 2015).

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