For the sake of time I had a pressure canner and hot water bath both going. The ph was 2.5-2.6 so hot water bath was safe, but only hold 6 quarts at a time and the pressure canner holds 7. This way each batch was 13 jars between the two. One jar cracked in the pressure canner and one cracked in the hot water bath. At first I thought I screwed up with the pressure canner and blew out the jar, but when the jar cracked in the hot water bath in the next batch I was fairly certain it is a jar issue. Also, there was no sign with the lids of over pressuring in either case. And the cracks extended to/from the bottom edge/corner of the jar in both cases also. I'm thinking hairline cracks are to blame. I should have checked the jars more thoroughly before filling and processing them.
