Materials and methods:
I prepared two identical 1L starters in 2L erlenmeyer flasks. OG of the starters was 1.038 (calculated, not measured). One starter was placed directly in the pressure canner. The second was placed in a covered stock pot. Both pots contained enough tap water to cover the flasks to the 750ml mark. Heat was applied to both pots at the same time.
At + 17 minutes the pressure canner reached 15psi and began to boil. The stock pot had been simmering several minutes by then.
When the sterilization cycle was complete (+ 15 minutes at 15psi) heat was removed. 30 minutes later the pressure had dropped to zero, the starter was moved to the counter top to cool, and the second starter was transferred from the stock pot into the hot pressure canner. The top was affixed, and heat was again applied. At this point the second starter (from the stock pot) had been immersed in boiling water for 62 minutes.
Operating temperature for the second starter was achieved at +72 minutes, and at +118 minutes the sterilization and depressurization cycle was complete.
Results:
The first starter boiled over losing roughly 100 ml of starter wort in the process. The inside of the vessel was covered with hot break from the wort's surface to the lip of the flask, and the aluminum foil cap was glued to the flask with evaporated wort goo.
On opening the canner the second starter was observed to have numerous large bubbles (roughly 2 to 3 inches in diameter) filling the flask. The interior of the flask was not noted to have hot break on it, the foil cap was clean, and no starter was lost in the sterilization process.
Analysis: Problem solved.
