Author Topic: Are these the right bricks for my Neopolitan oven?  (Read 3831 times)

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Offline ChristianVerschaeren

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Are these the right bricks for my Neopolitan oven?
« on: September 14, 2013, 05:54:35 AM »
So I'm building a low-dome Neapolitan oven.
I pretty much read this whole forum. Twice. So I'm pretty sure about what I want to do and how Im going to do it (apart from the traditional flue, I'll figure that one out when you guys do  ;) )

Yet I still have some questions pertaining to materials, as the stuff you get here and the tech terms to describe them here (Belgium) are not what you guys are using in the Commomwealth.


Before I was just planning on using these  bricks for the whole oven:
http://translate.google.com/translate?hl=en&sl=fr&tl=en&u=http%3A%2F%2Fwww.lebailly.com%2Ffr%2Ffichtech%2Fly40.htm
Based on the AL2O3 figure which is the amount of Aluminum Oxide in a brick I deducted this is what you would call 'medium duty' stones.

After reading Fagilia's thread, I know now I need floor stones with less 'Thermal Conductivity'.
Now, you guys seem to use a figure from 1.X to 0.3 that is the thermal conductivity of a stone.
I was wondering if there was a way to deduct the conductivity from these datasheets.

For instance, this brick has a lower AL2O3 content, but will it have the right thermal conductivity for a low-dome oven:

http://translate.google.com/translate?hl=en&sl=fr&tl=en&u=http%3A%2F%2Fwww.lebailly.com%2Ffr%2Ffichtech%2Fly18.htm

Hope you guys can help, thanx!


Offline stonecutter

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #1 on: September 14, 2013, 06:46:24 AM »
They will be fine for what you are doing.  Check out Forno Bravo forum for help too, there is more focus on oven building than anything else.
http://oldworldstoneandgarden.com/


When we build, let us think that we build for ever.
John Ruskin

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #2 on: September 14, 2013, 07:36:47 AM »
The more I learn about bricks, the less I know.  I know that the Whitacre Greer Light Duty bricks are the best domestic option for floors, but matching that in Belgium by looking at brick specs? Yeesh, that's tough.  To this day, I don't even fully understand which facet(s) gives the WG bricks the low conductivity that they have.

That being said, there may be a few data points that could help.

Density.  More air should translate into lower conductivity.  As the density drops, though, you should look at abrasion resistance- and that's not going to be on a data sheet.  You'll need to have a brick in hand with a knife to see how sturdy it is.

Alumina.  WG seems to contradict this, but, in theory, alumina is about 30 times the conductivity of silica, so lower alumina bricks should have less conductivity.

Color. This is probably not hugely important, but IR is a player in WFO thermodynamics. In theory, a lighter color floor should take longer to pre-heat and allow for slightly hotter ceiling temps, which, in turn, should foster better balance.

Belgium is not that far from Italy.  Have you looked into sourcing Biscotto di Sorrento?  I haven't known anyone, personally, with a floor that's needed to be replaced, but, from what I understand, these Neapolitan WFO floors eventually fail, so there has to be some kind of distribution network in place for replacement stones.  If you can, I'd hook into that.

Offline shuboyje

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #3 on: September 14, 2013, 10:58:46 AM »
Contact the manufacturer and ask for the thermal conductivity.  Most don't seem to publish this, but in my experience in the US they have it if you ask.  That is actually how I got the data for the WG bricks. 

They will be fine for what you are doing.  Check out Forno Bravo forum for help too, there is more focus on oven building than anything else.

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.
-Jeff

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #4 on: September 14, 2013, 11:45:31 AM »
You come from Belgium, this suplier has special bricks for building wood fired ovens:

http://www.broodoven.com/verkoop-vuurvaste-materialen

It is based in the Netherlands, close to the Belgium border. If you buy your material there, you will be sure it can be used for what you want to do. They have several different stones and tiles but like most supliers, no ready information on conductivity etc. I however believe, that if the stones are made from the same materials, like most firebrick are, they will have the same specifications. (I will reply to scotty's message about this also)

I come from Holland, speak dutch, and am currently in the same process as you are. Building a 100cm Neopolitan oven. I am starting the build next week. If you want to discuss some feel free to contact me.

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #5 on: September 14, 2013, 11:59:15 AM »
I know that the Whitacre Greer Light Duty bricks are the best domestic option for floors,

I looked into that last week. I did see the document you reffered to, looked at the specs of the stones because, also coming from Europe, I wanted to buy something simular. But when looking into that, I found the W-C stones are made of the same material as all other stones and they are vacuum pressed like most stones we have here are. Still, the thermal conductivity of the stones I found was a lot higher every time.

So then I noticed something on the document that supprised me but so far I did not have time to investigate further yet. They tested thermal conductivity of those stones and came to an average number of something like 0.65

However... from what I read, they tested those stones at very low temperatures. 30 celsius seems to be the highest mean temperature they used. That looked so strange to me... why test at those low temperatures because usualy, the higher the temperature, the higher the thermal conductivity will become. You allready see that in those test results. At 10 celsius it is 0.62, at 30 celsius it allready goes up to 0.69 Also, again something I do not know but was thinking about, is it not so that thermal conductivity is also influenced by outside temperature... If the stones are 10 celsius and outside temperature is 30 celsius, the thermal conductivity will be different from when the stones are 30 celsius and the outside temperature is also 30 celsius.

But I am not an engineer and have no idea about all those numbers. Maybe I am completely wrong. Then again, maybe I am not and those stones have the same thermal conductivity as any other stone made of the same materials and they just tested the wrong temperatures.....

I wanted to look into it before I posted about it but since it came up again I might as well post it now.

greetings

Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #6 on: September 14, 2013, 12:10:49 PM »
I'm going to take the other position and say that you might not want those bricks for the floor of your oven. I'm going to guess they are around 1.0 W/(mK).

There is no doubt that conductivity is closely correlated with density, AOTBE.  In the chart below, the blue markers are various alimina fire bricks. The yellow markers are the Promaboard and Duratec from fagilia's posts, and the red is the Whitacre Greer buff paver. As you can see, it is a bit of an outlier. The only thing I see (given the data available) that stands out between it and other similar alimina fire bricks is that it has a bit less porosity at 15% vs. 20-22% for the LY18, and ~28% for the other bricks of similar density in the chart. It has a higher alumina content than the LY18 (28% v 18-23%), but I don't think that is the difference as other firebricks in the chart with a similar density have a similar alumina content. Perhaps the manufacturing process is what results in the low conductivity?

All that being said, I agree with Jeff that you should call and ask about the thermal conductivity.
Pizza is not bread.

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #7 on: September 14, 2013, 12:22:49 PM »
Craig, that's a very informative chart.

I would expect an alumina content vs. conductivity chart to have W-G as an outlier as well.

If Jeff didn't have first hand experience with the W-G bricks providing better heat balance, I'd swear that W-G's testing methods had to be faulty.

Perhaps Tom could shed more light on this, but I just don't see the manufacturing process playing that much of a role in conductivity. You mix the ingredients, you vacuum press the bricks, you let them dry and then you fire them. I can't see it being any more complicated than that.

I'm telling you, every time I start pondering W-Gs specs vs. their conductivity, my mind twists up like a pretzel.  It's a puzzlement  ;D

Offline nachtwacht

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #8 on: September 14, 2013, 12:30:57 PM »
I'm telling you, every time I start pondering W-Gs specs vs. their conductivity, my mind twists up like a pretzel.  It's a puzzlement  ;D

And the temperature I wrote about, might that not unpuzzle it somewhat ?

Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #9 on: September 14, 2013, 12:32:55 PM »
Craig, that's a very informative chart.

I would expect an alumina content vs. conductivity chart to have W-G as an outlier as well.

If Jeff didn't have first hand experience with the W-G bricks providing better heat balance, I'd swear that W-G's testing methods had to be faulty.

Perhaps Tom could shed more light on this, but I just don't see the manufacturing process playing that much of a role in conductivity. You mix the ingredients, you vacuum press the bricks, you let them dry and then you fire them. I can't see it being any more complicated than that.

I'm telling you, every time I start pondering W-Gs specs vs. their conductivity, my mind twists up like a pretzel.  It's a puzzlement  ;D

I just saw this chart that suggests that manufacturing process is a factor: http://www.industrialheating.com/articles/89693-insulating-firebrick-maximizing-energy-savings-through-product-selection?v=preview

Pizza is not bread.


scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #10 on: September 14, 2013, 12:42:18 PM »
And the temperature I wrote about, might that not unpuzzle it somewhat ?

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.

Again, if we didn't have real world experiences of the W-G acting like .6ish conductivity, I might look more closely at the testing.  But we seem to have trusted members seeing the W-G act like the numbers they publish.

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #11 on: September 14, 2013, 12:52:37 PM »
I just saw this chart that suggests that manufacturing process is a factor

Craig, what are the figures on the x axis? Are these all the same density?  If they aren't, then density (caused by varying processes) is responsible for the differences, not the process.

Also, manufacturing processes for insulating bricks can get pretty complex, and thus might have an impact, but non insulating bricks, from what I've seen, use simpler methods.

Offline Tscarborough

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #12 on: September 14, 2013, 01:06:59 PM »
Vacuum forming them makes a fair amount of difference.

Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #13 on: September 14, 2013, 01:08:17 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.

Again, if we didn't have real world experiences of the W-G acting like .6ish conductivity, I might look more closely at the testing.  But we seem to have trusted members seeing the W-G act like the numbers they publish.

Unless you assume the trend is logarithmic in which case you get a rather interesting result.
Pizza is not bread.

Offline shuboyje

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #14 on: September 14, 2013, 01:09:58 PM »
I agree with everyone else, there is no explanation for the WG bricks.  The data sheet I received was from a third party testing institute, not in house testing, so that does lend some credibility to me. 

Could it be their clay?  Could there be some sort of organic component that is burning out and leaving microscopic air pockets?  This is all far fetched, but I agree with everyone else, if the constituents are fairly standard there doesn't seem to be any simple explanation.  It seems to me a different process would lead to either different constituents(like some form of cement for the cement line on the second chart), or a density in line with Craig's chart.

Interesting conversation.
-Jeff

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #15 on: September 14, 2013, 01:10:11 PM »
Vacuum forming them makes a fair amount of difference.

Vacuum forming removes air, which impacts density.  If manufacturing process is going to be the smoking gun here, it has to be independent of density (two bricks, same density, different process, different conductivity).

Offline TXCraig1

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #16 on: September 14, 2013, 01:12:34 PM »
Craig, what are the figures on the x axis? Are these all the same density?  If they aren't, then density (caused by varying processes) is responsible for the differences, not the process.

I believe the X is temp. They don't give detailed density data.

Density does not correlate to thermal conductivity when process is included:

Slinger       0.611
Extrusion   0.569
Cement       0.52
Cast          0.483
« Last Edit: September 14, 2013, 01:19:56 PM by TXCraig1 »
Pizza is not bread.

Offline shuboyje

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #17 on: September 14, 2013, 01:12:54 PM »
Vacuum forming them makes a fair amount of difference.

How common is that Tom?  I was under the impression from reading I've done it was pretty standard, but I know you have a lot of insight on the actual process in use at a lot of different brickyards.
-Jeff

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #18 on: September 14, 2013, 01:14:43 PM »
Unless you assume the trend is logarithmic in which case you get a rather interesting result.

 ;D

scott123

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Re: Are these the right bricks for my Neopolitan oven?
« Reply #19 on: September 14, 2013, 01:19:32 PM »
I believe the X is temp. They don't give detailed density data.

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.


 

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