Author Topic: Are these the right bricks for my Neopolitan oven?  (Read 3964 times)

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Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #20 on: September 14, 2013, 01:20:36 PM »
Temperature, that makes sense.  Then I can pretty much guarantee you that the conductivity variations your seeing for each process are due to changes in density.

Not so quick - I found the density data - look at the revision to my post above.
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scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #21 on: September 14, 2013, 01:43:17 PM »
Curses! ;D

I stand corrected, but, just to be fair, density does seem to correlate for cast (lowest density, lowest conductivity). When you remove cast from the equation, the variations are less significant, and, like I said, when discussing processes/and process based impact on conductivity, I believe non insulating and insulating bricks are apples and oranges.

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #22 on: September 14, 2013, 01:50:46 PM »
Unless you assume the trend is logarithmic in which case you get a rather interesting result.

Might make sence.....


Online shuboyje

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #23 on: September 14, 2013, 02:07:40 PM »
I'm curious if some of the others with WG bricks can chime in on their results.  I've personally cooked on these bricks at 1000F many times with no issues.  I know others with medium duty bricks around 1.4 end up with burning issues cooking at 800F.  I really think there is SOMETHING here, I just have no clue what it is and would love to hear others results.  I think Gene has the same bricks as I do in his oven and Robyn has the red version in her, although I'm not sure what their conductivity is but I would assume similar. 
-Jeff

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #24 on: September 14, 2013, 02:11:17 PM »
This data here:

http://www.traditionaloven.com/articles/84/firebricks-heavy-dense-fire-clay-bricks#comment-6095

shows a 37% alumina firebrick increasing .05 in conductivity from 400 f. to 800 f.  I don't think the increase in conductivity at higher temperatures is that significant.

The actual W-C test data shows an increase of .07 in conductivity from 10 celsius to 30 celsius. So at high temperatures it might not be very significant anymore, at low temperatures, it appears to be more significant....

Offline sub

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #25 on: September 14, 2013, 02:13:34 PM »
Hi Christian,

Raffaele Vassallo who used to work with Stefano Ferrara uses unistara STARMAX firebricks in his oven.

Quality: alumina <35%
Refractory brick pressed dry and is widely used in the production of fireplaces, grills and barbecues. Available in two colors.
chemical composition

     Al2O3 + TiO2 [%]: 19-21
     Fe2O3 [%]: 1.5

physical Properties

     Bulk density [kg/dm3]: 1,850
     Apparent Porosity [%]: 20
     Resistance to cold compression [kg/cm2]: 320
     Refractoriness under load [° C]: 1210

Online shuboyje

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #26 on: September 14, 2013, 02:24:14 PM »
Hi Christian,

Raffaele Vassallo who used to work with Stefano Ferrara uses unistara STARMAX firebricks in his oven.

Quality: alumina <35%
Refractory brick pressed dry and is widely used in the production of fireplaces, grills and barbecues. Available in two colors.
chemical composition

     Al2O3 + TiO2 [%]: 19-21
     Fe2O3 [%]: 1.5

physical Properties

     Bulk density [kg/dm3]: 1,850
     Apparent Porosity [%]: 20
     Resistance to cold compression [kg/cm2]: 320
     Refractoriness under load [° C]: 1210

But these are in the dome, he is using Biscotto for the floor.  The conductivity of the dome is irrelevant since it doesn't transfer heat to the pizza by conduction. 
-Jeff

Offline Tscarborough

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #27 on: September 14, 2013, 04:16:49 PM »
Not only does vacuum forming increase the density it also decreases the size of the pores.  That is why they have better absorbtion numbers.  Vacuum forming may be common in fire brick production, of the 2 producers that I am familiar with, one does and one does not.  And the one that does not is only 20 miles away and we still rail the W/G in from Ohio, that is how much better (because they are not cheaper) they are.

Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #28 on: September 14, 2013, 07:50:20 PM »
Not only does vacuum forming increase the density it also decreases the size of the pores. 

This is the key. Pore size is likely the second most important factor (behind density) with respect to conductivity, AOTBE.

As Tom noted, this is a function of the manufacturing process explaining why process matters. It also explains why the WG LD buff firebrick has such low conductivity.

1) Since conductivity is directly correlated to density, it stands to reason that AOTBE, the material with the larger pore size will be more conductive because it will therefore have less pores and areas of higher density. This is confirmed by the model in this paper: http://web.ornl.gov/sci/buildings/2012/1992%20B5/013.pdf

2) At high temps, radiant heat transfer will also be a factor. Heat moves through a porous material by thermal IR in addition to conduction. The higher them temp, the more IR is a factor (a fourth order relationship). When it comes to IR, I suspect the smaller the pore size, the less efficient the heat transfer as the thermal energy must be emitted, absorbed, and readmitted more and more times as the pore size gets smaller.

So, the efficiency of both conduction and radiant transfer decrease with pore size, thus smaller pore size = lower thermal conductivity, AOTBE.
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Offline stonecutter

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #29 on: September 14, 2013, 11:03:18 PM »


This is true, but there is little to no knowledge of Neapolitan ovens there, and little to no knowledge of the importance of thermal conductivity for the floor there.  If you want to build a Pompeii style SUV of an oven it is a great place, but if you want to build an oven to cook 60 second Neapolitan pizza there is a bit of a knowledge gap there.

That depends on who gives the feedback.
« Last Edit: September 14, 2013, 11:09:27 PM by stonecutter »
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Offline ChristianVerschaeren

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #30 on: September 17, 2013, 11:26:10 AM »
Wow, thanks for all the info, this is the most complete answer I got ever on any message board.

As suggested I called to know the heat conductivity numbers and got this by email:

Quote
Bonjour Monsieur,
 
Voici des valeurs typiques de conductivité thermique pour des réfractaires denses silico-alumineux  (température °C/lambda en W/K.m) :
 
30% Al2O3 : 200°/1.15 ; 600°/1.25 ; 1000°/1.3
40% Al2O3 : 200°/1.20 ; 600°/1.3 ; 1000°/1.35
60% Al2O3 : 600°/1.6 ; 1000°/1.65
 


So, not what I'm looking for. When I explained my situation he said that what I was looking for is isolating refractory bricks. Those bricks do have the  W/K.m values I am looking for.

But, and please excuse my complete n00b question here, is this even feasible? Because I guess this forgoes the whole concept of the floor being a heat sink doesn't it?


Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #31 on: September 17, 2013, 11:30:43 AM »
I guess this forgoes the whole concept of the floor being a heat sink doesn't it?

Conductivity works the same way in both directions regardless of material.
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Offline Tscarborough

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #32 on: September 17, 2013, 12:33:08 PM »
That is true, but for the purpose of a floor you also need mass, i.e. density, so the answer is, No, you do not want to use insulating bricks for the floor.  Aside from the fact that they are friable, they do not have enough density to act as a heat sink.

Offline sub

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #33 on: September 17, 2013, 02:40:20 PM »
But these are in the dome, he is using Biscotto for the floor.  The conductivity of the dome is irrelevant since it doesn't transfer heat to the pizza by conduction.

Yeah, my bad I've read too quickly  :-[

I don't know who else you can contact for the biscotto, I'll try to ask on italians forums.

Alfa refrattari Tavellone Rosso 50X50X5 are used by some members.

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #34 on: September 17, 2013, 04:00:03 PM »
I don't know who else you can contact for the biscotto

http://www.aversaforni.it/

Offline ChristianVerschaeren

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #35 on: September 17, 2013, 05:42:03 PM »
Great find Nachtwacht.  Wanneer vertrekken we? ;)

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #36 on: September 18, 2013, 01:50:04 AM »
Great find Nachtwacht.  Wanneer vertrekken we? ;)

It's half way Italy. I was thinking about holiday there next year but buying together it might be intresting to have them shipped over. No idea how expensive they are, I unfortunatly do not speak Italian.

Offline ChristianVerschaeren

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #37 on: September 18, 2013, 03:12:06 AM »
I can't wait till next year, the oven has to be finished by Milan- San Remo 'cause I already promised my friends a pizza party. :chef:

Either way, I've called and mailed around, I asked my le panyol dealer for for info on their conductivity hoping I could just buy the floor tiles, he should get back to me, but I don't really have high hopes on that.

Than I found these http://www.acrivi.com/fr/6-pierre-a-pizza-pour-pizzerias through gsans thread.
This http://www.acrivi.com/fr/pierre-a-pizza-pour-pizzerias/171-radiant-pierre-refractaire-dalle-a-pizza-pour-four-pro-morice.html looks promising, composition is refractory material, quartz and volcanic rock, and it's reinforced.
I'll keep you guys posted.

Offline sub

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #38 on: September 18, 2013, 04:12:31 AM »
Hi Christian,

Izzo Forni uses biscotto di Sorrento in their ovens.

Try to send an email  info@izzoforni.it

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #39 on: September 18, 2013, 04:16:59 AM »
http://www.fydrofire.com/_fydrofire/index.php/technical-data

Dutch company making specialized professional baking stones. Have not contacted them about the costs but their thermal conductivity, wich is what you are looking most at, is good. If my normal floor fails (in the process of making it now) I will put one of those on top was my plan. (or the Italian one....)