I'm planning construction of a small forge with a friend inspired by this one

http://ronreil.abana.org/minifor1.shtml

by Ron Riel. In researching Kaowool, I can't find a source for all the technical specs I want. For instance, what is the practical difference between #6 density and #8 density? I've ordered some ITC 100 for another project and plan on using it to treat the Kaowool inside this forge as well, but I've seen reference to needing something like ITC 200 to coat the "wool" first to toughen it up ...others make no mention of any need for such. Can anyone point me to a good source of info on these questions?