types:
  * All-Purpose - 9-12% protein. mixture between soft and hard wheat.
  * Cake - lowest protein content at 5-8%. from soft winter wheat. (or, make it from all-purpose + corn starch)
  * Pastry - soft wheat, 8-9% protein
  * Bread - 12-14% protein. higher percentage of hard red winter or hard red spring.
  * self-rising - baking powder and salt added during milling. Usually to pastry flour
  * whole-wheat - more of the wheat. Higher protein but doesn't form as much gluten. makes denser stuff.
  * Gluten-free - usually based on rice flour blended with tapioca, potato starch, xanthan gum
  * 00 - in the states we classify flour by protein content. In italy they classify it by how fine the grind is. 00 is the finest possible. Mostly used for pizza.