Two pounds of stone milled organic brown rice flour. Mix with water and grade 2 medium vermiculite to make your own PF Tek substrate jars or as an additional nutrient source in many other substrate formulas.
For an indepth explanation of how to make PF Jars check out the Let's Grow Mushrooms! - 2 DVD Set by Marc Keith.
For PF Tek Jars use 2:1:1 recipe
measure 2 units Vermiculite
add a little less than 1 unit water (be careful adding water, continue stirring while adding the water, only add enough until a small puddle forms under the verm)
continue stirring while adding 1 unit brown rice flour to evenly coat the wet vermiculite.