Help with pain au levain crust
I recently got Peter Reinhart's Artisan Breads Everyday. I've tried the pain au levain recipe 3 times and have had the same problem every time. The crust of the bread is a kind of pale gray color on top and a nicer golden on the bottom. And, although the bread does have a good spring, the crust doesn't really crack open on top (even where I've scored it). (See pictures below).
I'm wondering if anyone has any idea of what's going on.
I should say that I am using King Arthur French Style Flour (11.5% protein); I am using both starter and instant yeast; the dough is fermenting in the fridge for about 18 hours before baking; I preheat the oven to 500 Farenheit with a baking stone in the oven for 45 minutes; I pour a bit less than a cup of boiling water into a preheated baking pan on the rack under the stone; and I open the oven door for a couple seconds after 13 minutes and then bake for another 15-25 (depending on the size of the loaf).
Any advice would be greatly appreciated!