http://straightrazorpalace.com/forge...shiny-wip.html
This is my 6" pipe forge based on the great Charlie Lewis's set up and works fine for him

I used 1" 360 wool and applied 2 layers one was a split layer to half inch
Then applied a thin coat of Satinite now , my original high temp mortar did not last long

This gives me a 3" chamber sufficient for razors and I have made knives up to 2" wide with no problems either
So go for it I say
Hope this helps you mate