I am finally getting my forge pieced together. While doing more research on burners I ran across several information stating a forge needs to be lined with 2" of insulation (in my case I've chosen kaowool). However I have not ran across any information regarding the addition of satanite clay on top.

The forge I am building which the body is done, started as a piece of 6" diameter pipe. If I add 2" of Kaowool my opening will become too small to use. Will I do nine with 1" layer of Kaowool with some saranute or do I need the full 2" regardless?