Canning breads or cake.
When searching online for info on canning cakes at home experts agree that oven canning, particularly in a low acid product like a cake, is bad news bears. But what if you water bath can it? or pressure can it? I specifically want to can a sourdough batter which will have a ph much lower than 4.6. Other than it not being an approved recipe what could go wrong? One thing I can think of is the batter is going to puff up significantly during boiling and then collapse during cool down making calculating head space difficult. The composition of the atmosphere in the jar would also have a significant amount of CO2 from the leavening which, I'm guessing, would be unusual for a canned good.
Ball/Kerr and other reliable manufacturers have designed canning jars for moist heat conditions. "Oven canning" is a dry heat method and can cause the jars to break, so this practice is never recommended. Ball/Kerr doesn't recommend dry heat methods for canning in their jars.
The nature of starches, when heated, is to expand and thicken - at unpredictable rates. This will likely cause the lids to buckle or jars to explode in boiling water canners or pressure canners.