#101  
Old 06-01-2008, 06:01 AM
Peasant
 
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Default Re: Driving heat across the cooking floor

Hmmm...conflicting opinions....

I guess I'm not that worried about extra cutting time or effort for just the floor since I'm not going to be cutting that much (I think). If the high-duty brick would really make a difference over the many, many years I plan on using the oven, it would be worth it. Trouble is, I have no way of knowing if it would or not.
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  #102  
Old 06-01-2008, 08:00 AM
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Default Re: Driving heat across the cooking floor

From The Bread Builder's by Alan Scott and Daniel Wing:
"For ovens, it is fine to use standard low-duty 'fireclay firebrick,'...good to about 2,700 degrees Fahrenheit (1500 degrees Celsius), which is far above the temperatures you will ever achieve in your oven. Higher-percentage alumina bricks are more resistant to heat and abrasion (good for pizza hearths) but they have a disadvantage in bread ovens: the higher alumina brick is more conductive and may transfer an excessive amount of heat to the bottom of the loaf. Also, High-duty firebricks are actually less resistant to the cycles of heating and cooling such as those experienced by oven brickwork and are more likely to crack, spall and fail than standard firebrick. Low duty firebrick contains tiny voids into which the solid material of the brick can expand when it is heated."
That said, I am used medium duty in my oven (it is all I could get). I do experience burnt bottoms of my bread if I don't let the oven cool enough. (For the record, I think it is not that easy to cool the oven. I have to wait hours before I can bake after firing for pizza). I would not advocate having the hearth bricks on their thick sides. I have been regularly baking 25 lbs of bread after a pizza firing (I do have about 1" of extra mass - heatstop - on the dome, but no extra mass on the hearth), and I still cook a roast (or 3 last weekend) the next day, I don't think any extra mass in the hearth is needed. I know you this is just more conflicting advice, but in general, the standard plans seem to work the best: Low duty firebrick, hearth bricks on their flat sides, lots of insulation. If you plan to use your oven only for pizza and never for bread, you could consider the high duty bricks. But you will make fabulous pizza from a low duty brick oven and may have more trouble with bread from a high duty brick oven...

Hope that helps.
Drake
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  #103  
Old 06-02-2008, 02:25 PM
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Default Re: Driving heat across the cooking floor

Quote:
Originally Posted by cuda View Post
Three times the cost is reason enough for me.

In reference to medium/high duty brick: Would it keep the floor hotter, thereby making a better floor for pizza cooking, or just hold more heat for a longer period (btu vs. temperature), all other things being equal? Sounds like for our purposes there is no appreciable difference.
I heard good advice from the pro who builds the Artigiano oven. He can use any brick, and chooses a purpose made oven brick with alumina content around 30%. He says, "we cooking food here, not melting metal."

I like that.
James
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  #104  
Old 06-03-2008, 04:49 AM
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Thumbs up Re: Driving heat across the cooking floor

Then the solution is easy to decide.
Get your high temp bricks and try to cut them to fit "inside" of your full height soldier 1st course bricks. Build your oven as you wish and if you are not happy with the hearth performance, you simply remove it and replace it with the low fire bricks. In other words, don't build your oven on top of your hearth bricks.

Neill
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  #105  
Old 06-04-2008, 02:07 PM
Peasant
 
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Default Re: Driving heat across the cooking floor

That idea crossed my mind for a hot second (no pun intended), but I'm not interested in doing the floor twice. Actually, I'm really only curious for academic purposes. I'm sure that the countless ovens that have low-duty brick floors work great- I was merely wondering if anyone had any theoretical or practical experience with higher-duty floors for pizza.
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  #106  
Old 11-04-2011, 01:19 AM
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Question Re: Driving heat across the cooking floor

a question,
please redirect me if I am in the wrong place.
I am at the stage of base nearly complete and about to lay the floor / hearth.
3 inches of Hebel (aerated concrete) 2 inches of cal sil and 3 inches of fire tile.
I would like to make provision for thermocouples, either a tube or the device itself.
Any thoughts re material, placement, number , other relevant detail would be appreciated,
Oven is to be 42 inch diameter hemispherical shape much as per forno bravo plans.

Thanks

Dave Ly
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  #107  
Old 11-04-2011, 07:45 PM
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Default Re: Driving heat across the cooking floor

I have a thermocouple ( an old fashioned anologue type) in the side of my oven. I placed it about half way up the dome and used some stainless steel tube as a protective sheath for the probe. Stainless steel is not as good a conductor as copper. The sheath should not be a tight fit in the inner dome otherwise it will push out as the oven expands.
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  #108  
Old 11-04-2011, 08:49 PM
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Default Re: Driving heat across the cooking floor

I've been curious as to why one would want thermocouples. The hassle of installation, expense of purchase, display, etc... They are very cool but why not just shoot whatever with the laser. At the end of the day, we just want to know the temp, right? The laser is working for me but am I missing something? It seems like a lot of effort for little reward. JMO...
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  #109  
Old 11-04-2011, 09:16 PM
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Default Re: Driving heat across the cooking floor

Quote:
Originally Posted by david lyons View Post
a question,
please redirect me if I am in the wrong place.
I am at the stage of base nearly complete and about to lay the floor / hearth.
3 inches of Hebel (aerated concrete) 2 inches of cal sil and 3 inches of fire tile.
I would like to make provision for thermocouples, either a tube or the device itself.
Any thoughts re material, placement, number , other relevant detail would be appreciated,
Oven is to be 42 inch diameter hemispherical shape much as per forno bravo plans.

Thanks

Dave Ly
Dave you will get more replies if you start your own thread, unless you have the answer you seek.

Quote:
Originally Posted by Les View Post
I've been curious as to why one would want thermocouples. The hassle of installation, expense of purchase, display, etc... They are very cool but why not just shoot whatever with the laser. At the end of the day, we just want to know the temp, right? The laser is working for me but am I missing something? It seems like a lot of effort for little reward. JMO...
Same Les, nice toy but the laser gives me all the info I require too.
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  #110  
Old 11-04-2011, 10:08 PM
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Default Re: Driving heat across the cooking floor

People who are new to wood fired ovens always seem to be rather obsessed with reading temperature. After lots of firings your stopwatch hand and eye are enough. I always use the semolina on the floor trick (3 secs to turn black) to test floor temp. An infrared thermometer only reads the temp of the surface, so it has some limitations.
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