Author Topic: An Open Call to Ceramic Engineers- Reverse Engineering Biscotto di Sorrento  (Read 8043 times)

0 Members and 1 Guest are viewing this topic.

scott123

  • Guest
Chris, that video is for a raku technique.  The temperature is too low and too uneven for your purposes. You can't do this without a proper kiln.

I applaud your initiative, but digging up some clay is not the answer.  Your best bet is to do further research on the clay used in biscotto, and then purchase a clay that matches those specs. For instance, if they're using a clay that sinters at 800 C, then you'll want a clay that sinters at 800 C as well.


Offline sub

  • Registered User
  • Posts: 512
  • Location: Belgium
Well, I' ll try anyway, I don't want to buy clay.

I can past the quartz inversion stage, in my electric pizza oven     ::)

Here is a video of Marcello Aversa, from his website he fire the clay at 920° - 1688°F



I don't think he bought it, he's very traditional in his approach.

The biscotto must be undercook on purpose, there is no way they built ovens with a floor who need to be changed often without a reason behind it.


A COMPARATIVE STUDY OF MINERALOGICAL TRANSFORMATIONS IN FIRED CLAYS

scott123

  • Guest
Chris, I'm not sure if you're joking or not, but you can't use your pizza oven to fire clay :)

Different clays have different sintering temps, but 800C is about as low as you're going to want to go. That's 1472 F.  Your oven isn't going to hit that, and, even if it could, it couldn't maintain it evenly over the course of a few hours.

Kilns are highly specialized equipment.  They're insulated in such a way and have thermostats that regulate the heat so that they heat up very gradually and evenly over long periods of time (a day or more) and then cool down just as gradually.  It's this very gradual heating and cooling process that prevents your pottery from cracking.

If you watch the video you just posted, almost every shot captures an incredibly traditional approach- from appearances, almost everything you see could be from 500 years ago. The sole exception, though, is the brief shot of the kiln. That's a very modern/technologically advanced kiln. I don't recall seeing any shot of Biscotto kilns- most likely because they're not as timeless looking as the rest of the process.  I guarantee you that they're using modern equipment.

You've uncovered some important pieces of the puzzle, but, if someone's really going to reverse engineer these, they're going to need some serious ceramics background and equipment.  No offense, but it's not you- nor, for that matter is it me. Over the years, I think we've had members with the necessary background, so, hopefully we'll get someone with that kind of knowledge again.

Offline Hickory.Bill

  • Registered User
  • Posts: 9
  • Location: United States
  • I Love Pizza!
Have you considered a clay bonded fused silica.  Close in density and hardness to corderite (cheap pizza stone) but extremely thermal shock resistant. can easily go from 800F to ice water. Good to a use temp of 2200F.

Bill

Offline TXCraig1

  • Registered User
  • Posts: 12836
  • Location: Houston, TX
Have you considered a clay bonded fused silica.  Close in density and hardness to corderite (cheap pizza stone) but extremely thermal shock resistant. can easily go from 800F to ice water. Good to a use temp of 2200F.

Bill

The key requirement is extremely low conductivity not thermal shock resistance.
Pizza is not bread.

Offline Hickory.Bill

  • Registered User
  • Posts: 9
  • Location: United States
  • I Love Pizza!
The key requirement is extremely low conductivity not thermal shock resistance.

Ok, they you need to go with a composite system.

This is how high temperature refractory kilns are constructed.

The walls and ceiling are made from IFB, (insulating fire brick) as other have mentioned.   The deck is made with IFB and topped with a hard deck tile.

This photo shows loose fill, but it could be IFB.  It also shows piers to hold the weight.  Definitely needed if you have loose fill, but not for an IFB base if your not loading a lot of weight in.


Offline shuboyje

  • Registered User
  • Posts: 1134
  • Location: Detroit
Completely different then a kiln.  The oven floor directly contacts the pizza.  Therefore the thermal conductivity of the material that the pizza bakes on is incredibly important.  Any oven worth a darn has a composite construction with a dense floor and dome backed by a insulating layer.  What we are after in a specialized material for the inner layer of the composite system that will contact the pizza.  It needs to be suitable to serve as a hot face in a wood fired oven, but also needs to have a thermal conductivity of about 0.6 and currently it is not available in the american market above brick size.
-Jeff

Offline Hickory.Bill

  • Registered User
  • Posts: 9
  • Location: United States
  • I Love Pizza!
Completely different then a kiln.  The oven floor directly contacts the pizza.  Therefore the thermal conductivity of the material that the pizza bakes on is incredibly important.  Any oven worth a darn has a composite construction with a dense floor and dome backed by a insulating layer.  What we are after in a specialized material for the inner layer of the composite system that will contact the pizza.  It needs to be suitable to serve as a hot face in a wood fired oven, but also needs to have a thermal conductivity of about 0.6 and currently it is not available in the american market above brick size.


Ok then, how about a castable. Then you can make any shape you want.

Here is a fused silica castable that has a conductivity of 0.69 W/mK @ 600C.  the conductivity would be less at lower temperatures.

http://www.morganthermalceramics.com/sites/default/files/datasheets/1_fused_silica_cast.pdf


Or this one made from Calcined Fireclay with a conductivity of 0.72 W/mK @ 600C.

http://www.morganthermalceramics.com/sites/default/files/datasheets/1_hs_cast.pdf



And for lower conductivity there is Insulcast with a conductivity of 0.46 W/mK @ 600C.

http://www.morganthermalceramics.com/sites/default/files/datasheets/1_insulcast.pdf

You may be able to mix them to dial in the conductivity you want.


May need to call them about food safety.

Offline shuboyje

  • Registered User
  • Posts: 1134
  • Location: Detroit
Now we are talking Bill.  I've never found a castable in that range locally, and the only supplier in the area could care less to help.  The first two have really peaked my interest.
-Jeff

Offline TXCraig1

  • Registered User
  • Posts: 12836
  • Location: Houston, TX
Why not the last? I think 0.3-0.4 W/mK is where you want to be for NP.
Pizza is not bread.


Offline Hickory.Bill

  • Registered User
  • Posts: 9
  • Location: United States
  • I Love Pizza!
Why not the last? I think 0.3-0.4 W/mK is where you want to be for NP.

Likely the last one will be physically weak. 

As I eluded to in previous posts, only the last 1/2" or so need to be hard.   If you have 2" of 0.3-0.4 W/mK topped with 1/2" of harder 0.7 W/mK  you will not get heat transfer as if the whole mass was 0.7 W/mK.  There isn't enough heat capacity in the thin material to over cook the bottom.  Sure the 0.7 W/mK  layer will transfer the heat it has twice as fast as the thicker 0.4 W/mK layer, but once it's heat is gone, the heat will have to bleed up from the 0.4 W/mK layer at the slower rate.   Heat will also travel sideways through the 0.7 W/mK layer but as a practical matter it won't act like 2.5" of 0.7 W/mK castable.

Another idea would be to just get the calcined fire clay castable and split the batch when it's wet an mix in vermiculite or alumina bubbles with half and put that in the bottom of your form then top with the full strength.   Vermiculite is very cheap, but I'm not sure if there will be an initial burn off.  Alumina bubbles work great, but they are a bit pricey.  If you order alumina bubbles, make sure you know the volume, they are deceptive light.

Not sure where you guys are located, but you might try Southern Refractories in TX. TXCraig1 is from Texas.

http://www.southernrefractoriesinc.com/material-supply

Online Tscarborough

  • Lifetime Member
  • Global Moderator
  • *
  • Posts: 3478
  • Location: Austin, TX
    • Pizza Anarchy
Insulcast has a fair amount of perlite aggregate, so it is not suitable for a flooring material.  I have some 12x12x2" pavers that are made in the same fashion and fired to the same temps as the Italian biscotti, but they are not composed of exactly the same materials.

Offline stonecutter

  • Registered User
  • Posts: 756
  • Location: SC
    • Old World Stone & Garden
Why not the last? I think 0.3-0.4 W/mK is where you want to be for NP.
That's insulating firebrick range.
http://oldworldstoneandgarden.com/


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

Offline TXCraig1

  • Registered User
  • Posts: 12836
  • Location: Houston, TX
TXCraig1 is from Texas.

I'm lucky enough to have a biscotto floor.
Pizza is not bread.

Offline shuboyje

  • Registered User
  • Posts: 1134
  • Location: Detroit
I wouldn't want to build a floor out of anything classified by the manufacturer as insulating and not dense.  That says it can be used as a hot face, but probably in the context of a hot face for walls in a gas oven.  A floor in a wood fired oven takes a beating comparatively.

I've cooked lots of Neapolitan pizzas on WG at 0.6 @ ambient temperature.  I'm sure they go up a bit as the temperature rises.  For my oven designs I'm pretty confident 0.69 @ 600C would be adequate. 
-Jeff

Offline TXCraig1

  • Registered User
  • Posts: 12836
  • Location: Houston, TX
I've cooked lots of Neapolitan pizzas on WG at 0.6 @ ambient temperature.  I'm sure they go up a bit as the temperature rises.  For my oven designs I'm pretty confident 0.69 @ 600C would be adequate.

Have you tried baking on a piece of Fibrament in your oven at 600C?
Pizza is not bread.

Offline shuboyje

  • Registered User
  • Posts: 1134
  • Location: Detroit
Craig,

My post last night was clear as mud.

What I was trying to say is WG low duty buff firebricks have a thermal conductivity of 0.6 when measured at ambient temperature.  I think it is safe to assume that at 900F+ the conductivity has risen a bit.  I've baked a lot of Neapolitan pizza on this material and am happy with the results.  I think a Castable material at 0.69 thermal conductivity measured at 600C would be VERY similar to the WG bricks, if not a little less conductive. 

Have you tried baking on a piece of Fibrament in your oven at 600C?

I've never purposely baked at 600C, but the few times I have it hasn't gone well.  Once I oil fired my first oven with an experimental oil burner running on waste cooking oil.  Pizza burned to charcoal in no time.  The other time was a few months ago in my coal oven when I go it crazy hot to do Neapolitan.  That time I was on top of it to not burn the pie, but the drying effect of the coal at that temperature produced a very odd pizza.

Fibrament has never entered the equation for me due to it's inability to operate in direct contact with flame.  That obviously won't fly in a wood oven.  I might be able to get away with it in my coal oven, but that is so small and square so doing a brick floor was a no brainer compared to an experimental, expensive, custom floor.
-Jeff

Offline TXCraig1

  • Registered User
  • Posts: 12836
  • Location: Houston, TX
Right after I posted, I jumped in my truck. As I drove off, it hit me what you were saying.

In my oven at 600C on the deck, you need to dome the pie after about 20 seconds. 15 seconds later it's done.
Pizza is not bread.

Offline sub

  • Registered User
  • Posts: 512
  • Location: Belgium
I was talking to an owner of a four grand mère F 1030C about the benefits of a Biscotto floor, and He put terracotta baseboards as a temporary mod to tryout.

He is quite happy with the result,

before that he was burning the bottom of his pies when the floor temperature was above 750-770°F.
« Last Edit: August 09, 2014, 06:45:21 AM by sub »

scott123

  • Guest
Terracotta tends to be pretty low in conductivity, but it's also not very resistant to thermal shock, so I don't see it surviving all that long.