Michigan State University Extension
Preserving Food Safely - 01600940
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 may 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 PSIG BE APPLIED WHEN USING NEW PRESSURE CANNING EQUIPMENT. MOST MANUFACTURERS ALSO DO NOT RECOMMEND OPERATING THEIR PRESSURE CANNERS ABOVE 15 PSIG.
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.