Originally Posted by Zagut
"Glc perhaps a thick full shelf stone might show some temperature holding characteristics???"
That's where I was going. Thermal mass doesn't let the heat waft out as just hot air does. (Kinda like people)
My stone/stones are 3/4 inch thick and are the size of the shelf minus aprox 1/2 inch. They don't lose heat when the door is opened for a short period of time.
They take a while to get up to temp but once they are there they stay that way.
The reason that such a stone doesn't give you any significant temperature holding is that, as soon as the temperature drops, the oven fires up with a burst of heat to recover. A stone that has reached equilibrium is putting out the same amount of heat all the time (which is the heat it takes in), so it can't react to the temperature drop, being just a dumb stone. There's just not enough mass to compete with the elements in heating the oven.
The stone will, of course, maintain it own temperature far better than a baking sheet, but it's not doing much for the oven air temperature.
Now, in wood fired brick ovens, the mass is enormous. Takes a very long time to store up heat, but the brick mass itself is from that time itself the heat source and massive enough to recover the oven temperature.
When you look at how the stone affects the temperature as the oven element cycles on and off, you find that the stone moderates that cycle by a few degrees, detectable but not significant.