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It's just my opinion, but I think it’s easy to break oven curing into 2 major phases, drying the oven and breaking in the oven structure.
Drying of the oven.
For simplicity, oven drying relates to available, not chemically bonded, water. Unbonded water will be converted to steam over its boiling point, 212F or 100C at sea level, at altitude the temp change of course.
It’s easy to forget that even if the interior of the oven is above 212F / 100C the exterior will be something less, especially so when you’re salivating for your first pizza. The top of the dome will be hotter than the bottom of the dome structure. These differences in temperatures in the beginning are differences in wetness, and this creates a big opportunity to stress the oven unevenly and crack the oven. A wet brick will absorb heat to a greater degree than a dry brick and therefore hold the temperature down. This differential allows the dry brick to expand faster relative to the wet brick and I feel that it’s this difference that creates the majority of dome cracking seen during curing.
To avoid these cracks, dry the oven using low, slow, even heating. Ideally, though not particularly practical, the oven would be heated from all sides to just under 212F/100C and maintained at this temperature while dry air is circulated around the whole oven until the water is baked out. As I said this isn’t really practical, but my imagination goes to using some sort of oversized Christmas fan inflated snow globe with heat. The more practical answer is to warm the oven and keep it warm and dry while circulating air around the structure, passively or actively, until most of the available water has been removed from the brick.
Simple methods of gentile warming are placing light bulbs and space heaters in the oven while keeping a make shift door ajar. There are other methods of heating that can be found by digging around in the forums. Fires by their nature are more dynamic and so somewhat less controllable, but using fire was the only way that curing was done for thousands of years and done successfully. And, just because most of the water is gone a light bulb isn't likley to get your oven above that magic 212F/100C point. At the point where your temps are steady with a bulb, your going to have to graduate to some controllable fire. Be very conservative with these fires, go low and long if you can.
Breaking in the oven structure
In the second phase, the major problem is stress related cracking from thermal shock. The oven swells and contracts during curing cycles and the bricks, like shoes need a bit of time to fit just right. Heating the oven with a big fast fire, don’t allow the bricks of the oven structure to comfortably find their respective “happy places” within the oven structure. A large fast fire will heat the interior to high temps before any real change in temp occurs in the exterior of the oven. I envision that when the oven is young it’s like a great pair of new boots that hasn’t had time to become flexible. Again, Be very conservative with these fires, go low and long if you can.
You will be rewarded!
Chris
PS. Regarding insulation and curing;
It’s my opinion that early in the curing up to say 250F, insulating the dome has some downside relating to air movement and drying, I could be wrong here. After 250F or so, I think there are advantages to loosely insulating. The insulation should maintain a more even dome temp and therefore should keep thermal stresses to a minimum. Another advantage is that the oven will stay hot longer and this should help to dry the structure in a more homogeneous way. I could be wrong.
Drying of the oven.
For simplicity, oven drying relates to available, not chemically bonded, water. Unbonded water will be converted to steam over its boiling point, 212F or 100C at sea level, at altitude the temp change of course.
It’s easy to forget that even if the interior of the oven is above 212F / 100C the exterior will be something less, especially so when you’re salivating for your first pizza. The top of the dome will be hotter than the bottom of the dome structure. These differences in temperatures in the beginning are differences in wetness, and this creates a big opportunity to stress the oven unevenly and crack the oven. A wet brick will absorb heat to a greater degree than a dry brick and therefore hold the temperature down. This differential allows the dry brick to expand faster relative to the wet brick and I feel that it’s this difference that creates the majority of dome cracking seen during curing.
To avoid these cracks, dry the oven using low, slow, even heating. Ideally, though not particularly practical, the oven would be heated from all sides to just under 212F/100C and maintained at this temperature while dry air is circulated around the whole oven until the water is baked out. As I said this isn’t really practical, but my imagination goes to using some sort of oversized Christmas fan inflated snow globe with heat. The more practical answer is to warm the oven and keep it warm and dry while circulating air around the structure, passively or actively, until most of the available water has been removed from the brick.
Simple methods of gentile warming are placing light bulbs and space heaters in the oven while keeping a make shift door ajar. There are other methods of heating that can be found by digging around in the forums. Fires by their nature are more dynamic and so somewhat less controllable, but using fire was the only way that curing was done for thousands of years and done successfully. And, just because most of the water is gone a light bulb isn't likley to get your oven above that magic 212F/100C point. At the point where your temps are steady with a bulb, your going to have to graduate to some controllable fire. Be very conservative with these fires, go low and long if you can.
Breaking in the oven structure
In the second phase, the major problem is stress related cracking from thermal shock. The oven swells and contracts during curing cycles and the bricks, like shoes need a bit of time to fit just right. Heating the oven with a big fast fire, don’t allow the bricks of the oven structure to comfortably find their respective “happy places” within the oven structure. A large fast fire will heat the interior to high temps before any real change in temp occurs in the exterior of the oven. I envision that when the oven is young it’s like a great pair of new boots that hasn’t had time to become flexible. Again, Be very conservative with these fires, go low and long if you can.
You will be rewarded!
Chris
PS. Regarding insulation and curing;
It’s my opinion that early in the curing up to say 250F, insulating the dome has some downside relating to air movement and drying, I could be wrong here. After 250F or so, I think there are advantages to loosely insulating. The insulation should maintain a more even dome temp and therefore should keep thermal stresses to a minimum. Another advantage is that the oven will stay hot longer and this should help to dry the structure in a more homogeneous way. I could be wrong.
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