Author Topic: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento  (Read 7989 times)

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Offline Tscarborough

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #40 on: February 27, 2013, 09:51:11 AM »
OK, I just talked to my contact at W-G, the vacuum process is used to reduce the air entrainment.  I also asked him about slabs, but that is not something they have plans to do, although he does stock 6x12x1-1/4 firebrick which will work nicely for my next project.


Offline Tscarborough

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #41 on: February 27, 2013, 09:59:57 AM »
Out of curiosity, I ran our numbers for firebrick last year and we sold nearly 100,000 fire brick.  That is a lot of fireplaces for somewhere where it doesn't even get cold!

Offline Tscarborough

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« Last Edit: February 27, 2013, 10:53:27 AM by Tscarborough »

Offline Serpentelli

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #43 on: February 27, 2013, 01:01:21 PM »
Why?  What positive do you see from a lower conductivity at the cost of strength?  I cook on these at traditional Neapolitan temperatures and get traditional Neapolitan results.  I see no positive out of an even lower conductivity.  With my experience and the data I now have on these If I could get them in larger slabs I would take them over Biscotto any day. 

I agree, I don't see anything out of the ordinary, but again, we have data from a major brick and tile laboratory at a major university that directly correlates to every cooking experience I have on this material.  For a couple years I have been baffled by people complaining about their firebrick hearths be too hot and burning while mine worked perfectly.  Now it all makes sense. 

Jeff,

I would love to see a picture of the interior of your oven, especially the cooking surface. Although another WFO is decades away, I'd like to know that I have the most suitable material when I do eventually build one down the road!

Thanks,

John K
I'm not wearing hockey pads!

scott123

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #44 on: February 27, 2013, 01:35:29 PM »
Why?  What positive do you see from a lower conductivity at the cost of strength?  I cook on these at traditional Neapolitan temperatures and get traditional Neapolitan results.  I see no positive out of an even lower conductivity.  With my experience and the data I now have on these If I could get them in larger slabs I would take them over Biscotto any day.

Jeff, I'm not willing to trade conductivity for strength.  IF a particular chunk of Biscotto does actually clock in at .3 and will last, in a commercial environment for as long as a couple years, then I want that in a domestic option.

Now, bear in mind, my intentions go beyond Neapolitan oven owners.  It sounds like your W-G bricks could very well be the perfect domestic solution for John Q. WFO owner.  As far as deck ovens go, though, I have no idea that I'd ever find someone that needs .3, but if I can get a durable .3, I want it.  A few years back, I thought steel would be more conductivity than I'd need, and, more recently, I thought aluminum's conductivity was most likely way too high, but now I see both of these materials very differently.  As I consider .3, a part of me is saying that's ridiculous low and would most likely have no deck application, but... another part of me says 'you never know.'

Now that I see Tom's reference about Tuff coming in, on it's own, at .2 or .3, I'm pretty certain that .3 biscotto is a pipe dream. At this point, I'm not holding out much hope, but, if it turns out durable .3 can be done, I want it.

Btw, while we're talking about deck ovens, the best deck oven on the market, the Marsal MB, takes the top position because the low conductivity of the fibrament decks allows it to be be run at hotter temps while still maintaining good balance.  The W-G bricks have even lower conductivity than fibrament, and, since you're using them with direct flame, they are most likely far more thermally durable as well.  I, like you, would like to see these in larger sizes, but, other than that, these could easily blow fibraments out of the water and be the cornerstone for the next ultimate deck oven.

Offline Tscarborough

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #45 on: February 27, 2013, 01:49:26 PM »
FYI, I have replaced fibrament panels in a deck oven with W-G split firebrick and the owner really liked it.

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #46 on: February 27, 2013, 02:05:10 PM »
FYI, I have replaced fibrament panels in a deck oven with W-G split firebrick and the owner really liked it.

That's sweet, Tom.  Here I am thinking about doing it, and you've already done it.

Offline shuboyje

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #47 on: February 27, 2013, 06:22:21 PM »
Btw, while we're talking about deck ovens, the best deck oven on the market, the Marsal MB, takes the top position because the low conductivity of the fibrament decks allows it to be be run at hotter temps while still maintaining good balance.  The W-G bricks have even lower conductivity than fibrament, and, since you're using them with direct flame, they are most likely far more thermally durable as well.  I, like you, would like to see these in larger sizes, but, other than that, these could easily blow fibraments out of the water and be the cornerstone for the next ultimate deck oven.

Once you get to certain point this just becomes to inefficient to be a commercially viable option.  If an oven needs a stone with the same conductivity as Tuff, which is used as an insulator(obviously not a good one), isn't this a case of the wrong oven for the job?  Putting massively oversized burners under and stone with low thermal conductivity all in the goal of getting a heat balance with more heat on top seems like a mess.
-Jeff

Offline Tscarborough

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #48 on: February 27, 2013, 08:34:47 PM »
They do not use the tufa as a block, they use it as an aggregate, along with other materials so that it is denser and has a higher modulus of rupture, better abrasion resistance, and (probably) a lower thermal coefficient of expansion.  The mix also would probably tend toward the higher end of thermal conductivity I would guess, because of the cementious material used (volcanic pozzolans).

Offline shuboyje

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #49 on: February 28, 2013, 11:18:00 AM »
So Tom, just to sum up this conversation.  If someone wanted to produce a Biscotto like product domestically, I'm guessing they would start with fly ash and lava rock?  That I would have never guessed, lol.
-Jeff


Offline Tscarborough

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Re: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento
« Reply #50 on: February 28, 2013, 11:21:26 AM »
Pretty much.  I have fly ash and access to a different type of tufa, maybe I will make a mix.

Offline misterschu

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I'm planning to build a new pizza oven out of castable refractory in May so I've been looking at oven floor material, which seems to me to be very important and very hard to get right.  My past experience has shown that conventional firebricks are way too conductive.  For this effort I've been emailing some refractory manufacturers.  I emailed Plibrico and got a very positive response from them, though I'm unsure of the strength of these bricks.

Seeing that Biscotto di Sorrento is mentioned as having .3-.5 W/mC, Plibrico has two domestic firebrick options that are in the proper range. Can anyone advise on the durability of these?  I've uploaded the datasheets showing conductivity below, and linked the the MSDS on their site here: http://plibrico.com/uploads/MSDS/msds%20Pli-Bric%20IFB%2023%20%2026%20%2028%20%2030.pdf

Offline shuboyje

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Those are insulating bricks, and as such don't have near the mass you want for an oven floor.  They are 55 pcf density, my quick calcs say standard firebrick at about 8 pounds is around 151 pcf.  If you are already going the firebrick route, whitacre greer low duty fire bricks have proven to be the best choice, the only downside to them is you can't get them is large tiles.
-Jeff

Offline vtsteve

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In addition to the lack of mass, IFB is very soft and friable; it wouldn't hold up well to contact with peels/firewood/brushes.

Offline sub

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Hi

From my research the Biscotto is only composed of clay and water, hand pressed and dry for few weeks.

Forni Aversa: la lavorazione

Biscotto means first cooking (but not vitrified) in pottery, they fire the clay around 800C -1500F

Come Trasformare L'Argilla In Biscotto

The thickness is 5cm or 2"


Offline sub

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In the pictures, you can see impurities in the clay which make me think it's dug and used as is and not refined.

Biscotto from Aversa

scott123

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Biscotto means first cooking (but not vitrified) in pottery, they fire the clay around 800C -1500F

American potters use the term 'Bisque' or 'Biscuit.'  I wasn't ware that BdS wasn't vitrified.  As far as I know, cordierite and firebrick are always vitrified.  I can't help but wonder how the lack of vitrification impacts moisture in the exterior pizza crust as well as conductivity.

We've tested the absorption of vitrified ceramic materials (cordierite/firebrick) side by side with less porous materials like soapstone and steel, and the differences seemed fairly inconsequential, but the porosity of unvitrified ceramics is another story completely.

If BdS is truly unvitrified, then if you maintained a puddle of water on top, eventually, the bottom of the stone would weep with moisture. I'd be interested to see if this could be achieved.

As far as conductivity goes, this could be the missing link in understanding why BdS is so low compared to other materials.

In the pictures, you can see impurities in the clay which make me think it's dug and used as is and not refined.

Tom may be better able to address this, but it's my understanding that, for most industrial applications, clay is used in it's natural state.  That being said, aggregates are almost always added to clay in these types of applications, so the particles you're seeing in the photos most likely are added aggregate.

Offline sub

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As far as conductivity goes, this could be the missing link in understanding why BdS is so low compared to other materials.

The weight, they're light from what I've heard. 


Also the firing temperature can change the end up product from what I've learn about pottery:

Quote
The temperature a clay is fired to makes a tremendous difference. A clay fired at one temperature may be soft and porous, while that same clay fired at a higher temperature may be hard and impervious. 

From Aversa website: 
Quote
Prima di essere cotti nell'antica fornace a legna a 800 gradi, i mattoni vengono messi ad esssiccare per qualche mese nella stagione estiva, due nel periodo invernale.

Antonio Mastroianni   (another Biscotto maker from Casapulla) fire them at 930

Quote
Dopo la formatura, vengono messi ad asciugare a temperatura ambiente, dopo asciugato vengono inseriti nel forno a legno e cotti  all'incirca a 930 C.


« Last Edit: July 05, 2014, 05:40:50 PM by sub »

scott123

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The weight, they're light from what I've heard.

The supposed conductivity range of BdS posted earlier in this thread matches up with that of insulating firebricks.  BdS is light, but it's no where near insulating firebrick light.  There's more going on here- the lack of vitrification.

As you look at American firebricks and commercial WFO hearth materials, the choice seems to break down, across the board, to either vitrified ceramic or cast cement. That could very well be the reason why Americans can't find a domestic product that matches up to the Biscotto specs.

This knowledge could, to a small extent, open the door for someone interesting in making BdS domestically.  This is probably going to raise Marco's blood pressure ;) but I'm pretty sure a domestic analog clay could be found.  I'm not saying anyone with a kiln can do this- I've tried making molded ceramic tiles in the past and getting a final product that's perfectly flat is close to impossible. For the right person/people, though, there's a chance. This forum has seen potters/ceramic engineers in the past, but, unfortunately, none of them are presently active.

Still, though, I think there could be a market for this.

Offline sub

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The weight for a stone of 34,5x40x2,5cm is 4.7kg.

ps: It may be not very accurate, the thickness vary a Little, they are made by hand after all.

I will try to make a sample at home, I've dug up some clay,  used water extraction and let it dry, but the plasticity wasn't right, too much fine sand in it, I've screened it again, now it's drying hanging in a cloth bag.

For the kiln, this may do the trick:




 

pizzapan