I've been trying forever to get large, cavernous holes and a chewy texture in my whole wheat bread and I finally achieved success this week.  I tweaked a few things and I am curious as to which change made the real difference.  First, I added 1/4 tsp citric acid as opposed to the small pinch that I previously used.  I increased my retardation in the fridge from two hours at 38 degrees to 36 hours at 42 degrees (I use red star active dry).  I also increased my proofing time from 45 minutes to an hour and 15 minutes.  Finally, I increased my baking temperature to 425 with steam and.  I am just really interested in the science behind what I changed and how I can further take advantage of it.