Author Topic: boric stone / Mulite  (Read 2115 times)

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Offline SinoChef

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boric stone / Mulite
« on: April 19, 2012, 07:56:34 AM »

The manufacture of the oven I am working with is giving me two different definitions for my stone.

Boric stone and/or  Mulite

Anyone have a clue as to what either of these could be?



Offline SinoChef

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Re: boric stone / Mulite
« Reply #1 on: June 19, 2012, 09:03:11 AM »


anyone anyone, bueller bueller (scott 123) bueller bueller  :-D

"1. Biult-in hollow boron board" sic

http://www.alibaba.com/product-gs/398397522/Commercial_Electric_Stone_Pizza_Oven.html?s=p

Not that it matters that much. It works for me. Just curious. I need to let it rest for a couple minutes after 3 rounds of pies.

When its a little dirty, just crank it up to 500c, and it seems to absorb the carbon. Very little smoke. The board itself feels like it is made out of chalk.

Great little oven. The first one I had was bought used for about 100$ USD. 20 pizzas later, it paid for it's self.





scott123

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Re: boric stone / Mulite
« Reply #2 on: June 19, 2012, 11:11:19 AM »
I'm not sure how I missed this post.

From what I can tell, 'boron board' is a Chinese variation on the traditional cordierite baking stone theme, much like 'schamotte' is a European version.  Cordierite, mullite, schamotte, rokite (brand name) and most likely boron board are all pretty much the same thing- kiln fired silica alumina ceramic materials.  Within these materials, you're going to have different recipes, some with more alumina, some less, some with other trace elements (such as possibly boron) and different manufacturing processes, so the final products can have different resistances to thermal shock, density, conductivity and heat capacity, which, in turn, produces different baking properties, but... the ranges of properties you see in baking applications are usually not that wide. None of these materials re-invent the wheel.

Ceramic baking stones are almost always going have good resistance to thermal shock and a realm of conductivity between 1 and 6 (steel is 43).  While a pizza oven owner is going to have a hard time measuring conductivity (chemical breakdown from the manufacturer really helps), the one attribute that is easy to measure is density.  Density tells us a lot.  The denser the material, the greater the heat capacity per cubic inch and the greater the conductivity (air increases insulation). Density in baking stones is generally a positive trait.

The 'hollow' descriptor is giving off a corelite vibe:

http://www.mnclay.com/kilns/corelite.html

Corelite is great for potters that don't want to lug around heavy shelves or for manufacturers that want to save on shipping costs, but it's not so good for pizza ovens. It sounds like they get around the lack of thermal mass caused by a hollow core by having a material with higher conductivity than your average cordierite. The lack of thermal mass is causing the need for recovery time after 3 rounds of pies, but, thanks to the higher conductivity (and relatively high wattage elements), the stones are bouncing back quickly.

Is it safe to say that the hearth pre-heats relatively quickly as well?

I think, for many places in the states, a need for a couple minute rest would be completely unacceptable due to the fact that they have periods of the day with high demand and any kind of down time would leave them in the weeds.

From our other conversations, it sounds like the pace of Chinese pizzerias is a little slower, so a couple minutes isn't the end of the world. Should this recovery schedule ever become an issue, I'm relatively certain that you could do away with it with a solid stone.

Other than the stone, this oven seems to have some very impressive specs.  The wattage, for a thousand-ish dollar oven is through the roof and the peak temp is right on the money.  Does it have separate controllers for the top and bottom elements? The ad talks about 'temperature independent layers', but, it looks like 'layers' is their word for decks. I see 4 knobs, but sometimes these ovens have one knob as a temperature controller, but the other is a  timer.  Does this have 4 temperature controllers?

If it does have separate controllers, and is as durable as you're describing, they could sell a load of these to the American market.

Offline SinoChef

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Re: boric stone / Mulite
« Reply #3 on: June 19, 2012, 01:18:52 PM »
Quote
From what I can tell, 'boron board' is a Chinese variation on the traditional cordierite baking stone theme, much like 'schamotte' is a European version.  Cordierite, mullite, schamotte, rokite (brand name) and most likely boron board are all pretty much the same thing- kiln fired silica alumina ceramic materials.  Within these materials, you're going to have different recipes, some with more alumina, some less, some with other trace elements (such as possibly boron) and different manufacturing processes, so the final products can have different resistances to thermal shock, density, conductivity and heat capacity, which, in turn, produces different baking properties, but... the ranges of properties you see in baking applications are usually not that wide. None of these materials re-invent the wheel.

Scott123, one of my concerns. is this crap safe to serve off? China is great for some aluminum poisoning,  It holds temps, like I said. But, the stone does chill out. If it its busy, I just crank upper and lower. Wide open, 500c.

I dont want as an option. I can do it.

 But I want all of my guys to do what I do, so I can have a day off.

Quote
Ceramic baking stones are almost always going have good resistance to thermal shock and a realm of conductivity between 1 and 6 (steel is 43).  While a pizza oven owner is going to have a hard time measuring conductivity (chemical breakdown from the manufacturer really helps), the one attribute that is easy to measure is density.  Density tells us a lot.  The denser the material, the greater the heat capacity per cubic inch and the greater the conductivity (air increases insulation). Density in baking stones is generally a positive trait.

As you know. Quite funny, as I just had a local go off on me today for not buying her anemic bread oven.

Quote
Is it safe to say that the hearth pre-heats relatively quickly as well?

No, or if 1 hour is quick. Then ok. I have tried to make my own quuick za. poached.

Quote
I think, for many places in the states, a need for a couple minute rest would be completely unacceptable due to the fact that they have periods of the day with high demand and any kind of down time would leave them in the weeds.

From our other conversations, it sounds like the pace of Chinese pizzerias is a little slower, so a couple minutes isn't the end of the world. Should this recovery schedule ever become an issue, I'm relatively certain that you could do away with it with a solid stone.

All true. And pizza is not my bread and butter. It is a side, 60 other items to chose from.

It's a 4 hour delivery time here most days. 9p.m., umm I will have a pizza........... 1:30 am, maybe the guy comes...


Quote
Other than the stone, this oven seems to have some very impressive specs.  The wattage, for a thousand-ish dollar oven is through the roof and the peak temp is right on the money.  Does it have separate controllers for the top and bottom elements? The ad talks about 'temperature independent layers', but, it looks like 'layers' is their word for decks. I see 4 knobs, but sometimes these ovens have one knob as a temperature controller, but the other is a  timer.  Does this have 4 temperature controllers?
ff.
I bought a Rado here for 300$USD Good stuff.

I doubt this crap would make US specs. But it is a good oven. I would love to take a couple back with me. NSF? umm noo.

As your attorney, I would advise you to come here  and spec the crap they are selling!

enjoy....

http://www.alibaba.com/trade/search?SearchText=wood+fired+pizza+oven&IndexArea=product_en&fsb=y


Sell in America? The level of understanding you must have. To get A to point B is beyond me. But I have people here that can set you straight.

scott123

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Re: boric stone / Mulite
« Reply #4 on: June 20, 2012, 07:34:20 PM »
Earlier, you said the stone felt like chalk.  Is it actually chalky? When you rub a dark fabric on it, can you pick up a whitish tan residue?

For a commercial deck oven, a one hour pre-heat is very quick.

If American Neapolitan pizzeria owners can get non UL listed Acunto ovens approved by fire inspectors, then I think they should be able to get something like this passed.  When I talk about the 'American market,' though, I'm really referring more to the home baker than the pro. We've had quite a few members who are pleased with their Chinese Sage brand countertops. This is, imo, just a step up from that, and, since Sage is generally MIA these days, this would be a lot more readily available. I'm not necessarily saying that these ovens are the best thing since sliced bread, but this is most excited I've ever been reading the specs of a $1,000 oven.

I know, it's $1,000 for you, but after an importer marks it up, it's probably $2K for me, so my excitement is probably a little unfounded, but even for $2K, this might not be bad- if it's durable.

Would you happen to know if it's $1000 per 'layer' (deck) or if it's a grand for both decks?

Offline SinoChef

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Re: boric stone / Mulite
« Reply #5 on: June 21, 2012, 08:18:23 AM »

As of this afternoon. The double deck was 920$ USD. The single deck was 460$. And this was from an outlet, not factory direct.

"20 prices for everything in China". Ali babba is giving you a very high price. The love to negotiate here. It's part of business.

Out of the box I was picking up a lot of powdery substance. But after a couple days it stopped. It feels like you could run a screwdriver over it, and scrape out some veins. 

It does not flinch at 500 c.,(900 f). Kicks out some heat from the vent. But seems to be well insulated. A little bulky for a home kitchen, but would work well in a garage.

scott123

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Re: boric stone / Mulite
« Reply #6 on: June 21, 2012, 03:36:28 PM »
$460 for a single deck, huh?  All we need now is an enterprising, Chinese speaking ebay seller that will mark it up to $800 and ship it for another $300 and we have a pretty major competitor to Sage.  Of course, it is, as you said, only for those with the space, AND only for those willing to go through the trouble of wiring it.

Are you using metal peels on the deck?  If you're really concerned, I might stick to wood.  I know the Chinese have a really bad track record when it comes to toxic materials, but they'd have to be really stupid to put heavy metals in a baking stone.  It's probably not all that tasty, but my guess is that eating stone dust would be comparable to eating clay, which is perfectly safe. If this thing gives off bigger pieces than dust- like say a small pebble ending up in the pizza, that could wreak havoc on teeth and put you in a difficult legal situation.

From your description, it sounds like the baking stone wasn't fired to a hot enough temperature and the clay particles didn't have a chance to bond.

Offline HickoryBill

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Re: boric stone / Mulite
« Reply #7 on: July 02, 2012, 07:56:54 PM »
Mullite is a generic term for an alumina / silica material.  Corderite is a Alumina / Silica / Magnesia Blend.

Both "blends"  can have a wide range of properties, depending on their actual composition.  For example, mullite can range in alumina content from 40% to 70%.    Not sure of boric stone, but as others have said, you need to find out what the actual chemistry is to make a sound decision.

Offline SinoChef

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Re: boric stone / Mulite
« Reply #8 on: July 04, 2012, 05:57:00 AM »
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Are you using metal peels on the deck?  If you're really concerned, I might stick to wood.

Can't find either in the small market I am in. Had to go online and buy from the Chinese version of Ebay. I prefer wood peels and that was all we could find.

Quote
From your description, it sounds like the baking stone wasn't fired to a hot enough temperature and the clay particles didn't have a chance to bond.

I would bet money that is correct. Is 900F enough to continue the bonding process? Or is it a one time shot in a kiln?

One of my guys decided he did not have time to wait for our regular oven to free up, so he braised some pork knuckle in the oven, (I repeatedly stated, and translated) was only for pizza. So I had pork grease spatter every where in it.

The grease stuck to the stone, discolored it and took the "chalky" feel off of it. I cant burn it off anymore. Aside from making the oven smell like crisp pork skin. It seemed to help.

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All we need now is an enterprising, Chinese speaking ebay seller that will mark it up to $800 and ship it for another $300

The only people I know here that ship, do it by the container.  :-\

But anyway, thanks for taking the time to respond. It works well for me. Just a year or so on this site, and I get more curious as to "why" questions. And I wanted to be sure I was not serving toxic pizza to people, Cause I eat them too! :o

Thanks!

scott123

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Re: boric stone / Mulite
« Reply #9 on: July 04, 2012, 07:11:57 AM »
You're welcome.

The bonding process would require kiln temps well above 900, but could be done any time. Anything ceramic that's glazed has been fired twice, once at a lower temp, and, after glazing, at a higher temp.  It isn't until the second firing that the clay particles fuse and the pottery can hold water.

This would involve a massive amount of trouble, but if you knew a potter with a large enough kiln, you could fire the stones.  You'd have to figure out the correct temp to fire them to, which would both involve sacrificing a bit of the material (a small strip) and quite a lot of time testing. It totally wouldn't be worth the effort- I just wanted to share that it could be done.

That's good news about the pork fat. I'm guessing that it's safe to say that you're not running your oven very high?  In a NY oven running at 650, pork fat wouldn't last long.


Offline SinoChef

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Re: boric stone / Mulite
« Reply #10 on: July 04, 2012, 08:04:49 AM »
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It totally wouldn't be worth the effort

I agree. I would have to damage the oven to get the stone out. Or at least disrupt the metal seals/lip that is holding the stone in. It makes good pizza. I am happy. It was just the texture of the stone I was uneasy with. So next time i will season the whole thing with bacon strips to start. :)

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I'm guessing that it's safe to say that you're not running your oven very high?

It was my morning crew, I usually don't fire it up till around 4 p.m. Minimum heat on it is 100C, or 220F. They usually do the shanks at around 370F. It was the low ceiling and exposed elements on the upper that caused the spatter. Pizzas I do,do around the 650 mark.

Offline HickoryBill

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Re: boric stone / Mulite
« Reply #11 on: July 04, 2012, 01:49:00 PM »
Out of the box I was picking up a lot of powdery substance. But after a couple days it stopped. It feels like you could run a screwdriver over it, and scrape out some veins.

Typically a corderite is fired to 2200F  and a mullite to maybe 2400F.

There of courses shouldn't be any powdery material.  If it goes away and doesn't come back it was probably just dust from the factory.  Ceramic plants are very dusty.

Any kind of soft vein would indicate poor mixing, or that some other material (different ceramic material) was inadvertently  blended in with your ceramic. 

My big concern would be trace levels of heavy metals such as nickel, cadmium, etc that could have been in the original ore and clay.

There are labs that can test a very small sample, but I'm not sure what they charge.