To get a more open crumb, the dough needs to be wetter, to the point where
it may be difficult to handle. There are good discussions of this in the
Bread Baker's Apprentice by Peter Reinhart, The Village Baker (blanking on
the author's name right now) and I think I rmeember a good discussion also
in Bread Alone by Daniel Leader (sp?). But basically the dough needs a
higher percentage of water; also, a moderate level of gluten like an
all-purpose rather than a bread flour will help (too much gluten will
contain the gas in smaller bubbles). The best results I've gotten for this
type of bread were a recipe called Pain L'Ancienne from Reinhart's book, in
which I use a moderate gluten flour, knead up the dough with cold water,
retard it overnight in the refrigerator, then gently shape it and let it
rise to bake the next day--with just that one initial kneading and no
punching down. It makes a wonderfully open holey crumb.
Diane Brown