Bread Science
I came across this investigation researching an indirectly related subject--general gas permeability of baked bread.
http://digital.csic.es/bitstream/10261/39916/1/J%20Food%20Engineering-2012-108-128.pdf [1]
It deals with the effects on crumb, oven-spring and, especially, crust when baking dough is subjected to varying amounts of steam.
I found it interesting, and--if I read it correctly--in some cases "less is more". For example, we like a thin, crispy crust, and a light crust color in baguettes. I typically steam baguettes for only 10 minutes--reasoning the thinner loaves will have reached their limit in oven spring in that time. The investigation reports this relatively short steam exposure also contributes to a lighter crust.
I found this report quite readable. Although I have a science background, it's not a food science background. Consequently, I frequently find reading food science reports difficult. This one isn't.
David G