Not enough heat

Posted by Richard Stybak on September 19, 2004 at 03:57:59:

Rado; Thanks to you I finally understand why there is not enough heat and have taken steps to correct this problem. I climbed inside and removed the stainless steel and the insulation one layer above the stainless. I now have facing the fire in order going up; approx 1 " refractory cement, then 1" insulating blanket and lastly capped off with another 1" of refractory cement. I am now thinking of lining the inside with fire brick, but that poses problems I need some help with.

Fire brick being 4 1/2 " wide I would lose 9" from my 34" wide hearth floor So, On top of the oven floor, I have laid a piece of steel flat-bar on top of small firebrick shims (2"x2 1/2") and laid 4 courses of brick without mortar. This maintains the 34" width. Now after these 4 courses the arch of the dome begins, so continuing laying the brick on the flat becomes very difficult. So here are my questions; Do I need to use mortar in the joints ? Will starting the brick 2 3/4" above the hearth floor be OK?

How about other voids or air spaces, do they have to be filled with mortar so that the mass is solid to the existing dome? After the first 4 courses can I lay the brick on edge, putting the 2" side down? This would cut the depth of the mass to 3 1/2" on the dome as opposed to the mass of the first 4 courses which would be 5 1/2'.

Of course any other ideas you have would be welcome.

PS: The castable refractory cement is difficult to trowel vertically, let alone overhead.