Preheat combo-cooker?
I've been baking two loaves at a time, one in a cast-iron Dutch oven (4 quarts, deep bottom), the other in a cast-iron combo-cooker (3.2 quarts, shallow bottom), and the loaf in the combo-cooker seems to cook faster and darker.
I preheat the oven at 475°F for about 50 minutes, bake covered 30 minutes, finish uncovered 20 minutes. During the preheat, I use an oven thermometer to gauge when my cast-iron cookware is up to temp, and I've noticed some variation depending on whether I place the thermometer in the Dutch oven or in the combo-cooker, and where I place the lids.
The combo-cooker has less mass than the Dutch oven, so it preheats faster, and I suspect this plays a part in the difference in the finished loaves. I might try putting the combo-cooker into the preheating oven a few minutes after the Dutch oven to try and even things out.
What sort of preheating arrangements have people found to work well when using a combo-cooker? Lid on, lid off, no preheat, lid-only preheat, etc.?
For context, I'm working through the recipes in Ken Forkish's Flour, Water, Salt, Yeast.
My mental picture of how hot air circulates in an oven, with or without a convection fan, leads me to believe that pots will come up to temp faster when the lids are off.
For two vessels, I would put the lids on one rack and the two pots on another.
When I use a combo cooker, I preheat the bottom part on a burner on my range for 5 minutes or less to get around 400 to 500 F. I don't see the benefit of preheating the top - normally we want to top to expand, not cook, at the beginning of the bake.