John's pic of the kiln build has inspired me to dust off plans for a small soft brick cantenary car kiln. The 2 kilns I previously built were dry stacked but I noticed John used a mortar.
I was wondering if it is fireclay used for leveling each course or kiln cement to hold the brick in place. my concern is material from the mortar, falling into the pots during firing. My last 2 kilns were sprung arch with ifb in the arch that contained no sand, those were used in the side walls.