Giving No-Preheat a Try
With warm weather and more time spent in the garden than in the kitchen these days, I finally decided to give the "no-preheat" method  a try since ehanner, crumb bum, sourdough-guy, and many others seem to like the results and the ease (not to mention energy savings).
I must admit I have been very skeptical of this method, it goes so against the grain of how I have made bread my whole life - I couldn't bring myself to do it for the longest time after carefully making each batch of dough, not wanting to sacrifice it, and I was convinced people who liked this method didn't require a thick, crispy crust like my family does - maybe it works fine for sandwich loaves, but crusty, chewy hearth loaves? Bread is sacred to my French husband and not something to be trifled with (he often hovers about the kitchen while I'm baking to make sure I hear the oven alarm and don't ruin the precious bread...)
So this past weekend I made a double batch of both the Thom Leonard  and the Columbia  (both from Glezer's ABAA) and decided to try the Leonard as the no-preheat and compare it to the Columbia which I would do on the hot baking stone as usual. First, as I mentioned to Zolablue in another blog, this weekend's bake was different than any previous sourdough bake I've done since starting back in November in that with the warm weather and warm house temps (70-75F) my starter was incredibly active and I've never seen these same doughs rise as much in the same time period as they did this weekend, they nearly blew the lids right off the dough buckets I use.
So I was a little worried the dough would be over-proofed, but when I slashed the Thom Leonard loaves after flipping them out onto a cold parchment covered baking sheet they seemed to hold their shape well. I put them in the cold oven on the middle rack (baking stones removed) and turned the oven on to 425F to bake the whole time, no steam or mist (needless to say, my husband was probably more nervous than I was...). I kept the light on to watch, and I noticed the slashes opening up and the loaves spreading - and I thought "great, I'll end up with pancakes", so I was extremely surprised to check back about 10 min later to see the loaves had bloomed and rose up very high - good oven spring - I was impressed! I left them in for about 15 min. before I opened the oven and rotated the loaves, then let them get nice and brown for another 15-20 minutes. I took them out when they looked nice and brown and the internal temp was about 204 . The crust felt nice and hard as they always do when you first take them out of the oven, but I knew the real test would be once the loaves cooled and we could cut into them and taste them. I should also mention that I have a gas stove, so the oven pre-heated and reached 425F pretty quickly without the stones in there.
Results below: we were very pleasantly surprised at the oven spring and open crumb, and the crust was crispy, but thin. Still, I could live with that considering how easy this was to do, no waiting for the stone to heat up, no misting, etc.
For comparison, below in front are some Columbias that I baked on a hot stone that I let heat up to 500F after the oven was already hot from the previous bake, then turned down to 400F after misting first 2 minutes. No-preheat Leonards are in the back. I made these Columbias as very large 3 lb boules rather than the usual batards (I like this large shape as it seems to keep the bread fresh longer throughout the week with just the cut side wrapped partially in foil). These Columbias also had tremendous oven spring, height, and open crumb, in fact they had better height and more open crumb than the no-preheat Leonards, and they also had a very thick crisp crust, which we prefer over the thin.
That said, I am still very happy with the no-preheat results given how easy it is, and will continue to use this method throughout the hot weather when I'm using the oven less anyhow. So I tip my hat to Sourdough-guy, ehanner, crumb-bum, and others who use this method, I've learned much from your advice before, but on this particular one I was skeptical, I'll never doubt you again...
Still, in cooler weather we cook so much on the weekends in the oven that I prefer to keep the stones in place, and my husband definitely prefers the resulting thick crust. Here is a crumb shot of the Columbia baked on the hot stone.