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 recommended because processing times for use with
current models have not been adequately researched. Because steam canners do not heat
foods in the same manner as boiling-water canners, their use with boiling-water process times
may result in spoilage. 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. One-piece zinc porcelain-lined caps are also no longer
recommended. Both glass and zinc caps use flat rubber rings for sealing jars, but too often fail
to seal properly.
This document was extracted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA (Revised 2009).
How do I?
Cure & Smoke ·
Make Jam & Jelly ·
Seasonal Tips ·
Info Request ·