With oven sterilization similar problems arise as with the microwave: The heat conduction of dry air compared to steam (as in the pressure cooker and a covered pot of boiling water) is much smaller - therefor the sterilization time has to be longer -> this dries out the substrate.
With oven sterilization similar problems arise as with the microwave: The heat conduction of dry air compared to steam (as in the pressure cooker and a covered pot of boiling water) is much smaller - therefor the sterilization time has to be longer -> this dries out the substrate. Raising the temperature of the oven much over 212°F will dry the substrate even further. Colonizing substrate needs adequate water to colonize, otherwise it either won't start or will halt mid colonization.
There is a workaround though that eliminates the problem of drying the jars out:
Get yourself a casserole with a lid, put the jars in and add water 1/2 of the height of the jars, and put in oven at 350°F for at least one hour. Better 90 minutes to be sure.
Check for the water level during the procedure, don't let the water completely evaporate.
This sterilisation method is equally good than boiling or steaming in a pot with lid.
