From: What makes a bread either close or open crumbed/textured? Oven spring Yeasts continue producing CO2 until they die at 60C/140F. Also, gasses expand with heat, so it will also help ...
A recipe that I am trying says that it's very important I follow the instructions to the letter. However, at one point it says "Each loaf should bake at 300 degrees Fahrenheit in convection/steam oven ...