High duty fire bricks Getting Started Discuss High duty fire bricks in the Pizza Oven Design and Installation forums; I purchased several pallets of high duty fire bricks cheap. I have decided to use them on the hearth only. ...

[M.J.FULLER]

I purchased several pallets of high duty fire bricks cheap. I have decided to use them on the hearth only. My reasoning is that they will tend to get hot and stay hot- this would seem to be an advantage. How many people have posted on this forum complaining that the hearth is not hot enough to cook their pizza bases? (possibly a technique peoblem).
I also remember seeing in Alan Scotts book a comment that high duty bricks were good for the hearth (I think). I also saw a post on another forum about 5 years ago from Canada. This oven builder owned a foundry and built his entire oven from high duty fire bricks. He said he had no problems.

I am in the middle of the build. I will let you know how I go.

[Johnny the oven man]

Low duty refractory bricks are usually in the 18-26% AL203 grade with med. duty about 26-45, and superduty 45% and up. Density usually increases as alumina content increases. Most firebricks are dry pressed, but you can get extruded/ wirecut poor quality product. We sell 40% grade f/bricks to the general public for their WFO's.

[Abear]

I've finally finished our oven with medium duty bricks (40% alumina content) and I can honestly say I'm quite pleased with the bricks. It takes about 1.5-2.0 hours to get about 850-900 degrees on the dome and 650-700 on the hearth. After a round of pizzas, we've done oven-dried tomatoes and brisket overnight with fantastic results! At 12PM the next day, the walls are still reading 250 degrees. I wouldn't be worried about using medium duty bricks - if they're cheap, use them!

[Neil2]

I suspect, that for pizza and bread ovens, there is no practical difference in heat up time or heat retention between "high duty" and "low duty" firebricks.

[gpappas]

Where can I get BF Varnon Slabs

[Johnny the oven man]

I think Varnon are made by AP Green?

[fornax hominus]

I built my oven with a combination of med and hi-duty bricks .. all salvaged and some vintage from steamship boilers.. I did come across some ''chief'' #1 arch bricks which I used on row 6 , they are the last bricks to lose their soot as they have more mass the further they go into the dome , and I mortared them in . After parging with mortar I put a layer of extreme heavy duty aluminum foil [shiny side in ] over the whole oven , before the ceramic fiber layer. I also have a floor of 3x5x7in. hi dutys and they do hold their heat!!
One aspect that hasn't been mentioned so far is that hi-dutys weigh more! so they have to take longer to heat up , and longer to cool .
I am tossing a handful of snow in these days to add moisture for the bread.. it vapourizes fast!!

[fornax hominus]

Originally Posted by Johnny the oven man

I think Varnon are made by AP Green?

I may be wrong [what? Again?] but I think AP green is no longer with us.
tim

[dmun]

There was a big consolidation of the refractory industry a few years back, I think partly because of asbestos liabilities. I think AP green was absorbed into the Harbison-Walker refractory conglomerate. Now HW is about the only game in town in the US.

[fornax hominus]

Oh! Asbestos! ... great! I bought and am still using on my kiln a stash of AP Green's EPG50 insulating cement .. grey , fluffy and they claimed no asbestos... they claimed.. sigh!! .. Anybody heard a discouraging word on this?
tim