Author Topic: Sillimanite Kiln Shelf  (Read 1588 times)

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Offline breadman_nz

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Sillimanite Kiln Shelf
« on: December 16, 2011, 05:16:40 PM »
I just bought a sillimanite kiln shelf from these guys (16" x 16" x 3/4") to replace my cheapo thin ceramic round stone. (http://www.potterysupplies.co.nz/shopexd.asp?id=629)

Haven't used it yet, but I understand it should be very similar to cordierite, which no-one locally seems to sell. My oven gets to about 560-570F, so again, this should be able to do a good job on a 4-5 minute NY-style pie.

I can't find anything that suggests sillimanite kiln shelves are toxic. I could still be in the market for a fibrament or cordierite stone (imported from the USA), such as the Best Manufacturers UC-500 (cordierite/porous ceramic) or the Old Stone Oven 14 x 16" (cordierite too, I believe)

Will report back in due course.

Any further thoughts on sillimanite / the other options above?


Offline Jet_deck

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Re: Sillimanite Kiln Shelf
« Reply #1 on: December 16, 2011, 05:20:08 PM »
Did you consider cooking on steel plate?
Her mind is Tiffany-twisted, she got the Mercedes bends

Offline breadman_nz

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Re: Sillimanite Kiln Shelf
« Reply #2 on: December 16, 2011, 06:28:28 PM »
Yes, but a kiln shelf was easier to get hold of. Also, reading Scott123's and other postings here, my oven gets warm enough to go with a cordierite (? also sllimanite) type stone.
« Last Edit: December 16, 2011, 06:36:50 PM by breadman_nz »

Offline scott123

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Re: Sillimanite Kiln Shelf
« Reply #3 on: December 17, 2011, 05:50:02 AM »
Breadman, while I applaud your 4-5 minute baking goal, your desire to get a better stone and the research you've done toward this end, I don't think this stone will perform as well as you expect.

From the photo, it appears that sillimanite is just another word for cordierite.  To do successful NY bakes, cordierite generally has to be in the 600+ realm.  I'm in the process of looking at a special high alumina kiln shelf that might be able to do 4 minute bakes at 570, but that's only at an inch thick.

You could do some homework and get the density of the stone (by finding out the weight) and contacting the manufacturer to establish alumina content, and that will go a long way in predicting how it will perform, but even in a best case scenario, you won't break a 7 minute bake at 570. I've been talking a bit about gentle oven mods lately, and perhaps if you can squeeze another 50 degrees out of your oven, you might be okay.

Otherwise, I highly recommend 1/2" steel plate.  By the time you pay shipping for an American kiln shelf or baking stone, steel will be far less expensive and outperform them all.

Offline breadman_nz

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Re: Sillimanite Kiln Shelf
« Reply #4 on: December 19, 2011, 03:10:37 AM »
Thanks for the advice so far!

Two updates:

1) We had a major pizza baking session this weekend, feeding about 30 people (24 pies in total). Two pizzaiolos (me and my brother). Had a simple, el-cheapo round stone on the top shelf, and the sillimanite block on the lower shelf. Didn't have an oven thermometer, but I'm not convinced the electric oven was very hot at all. The sillimamite shelf cooked well - but both top and bottom shelves were taking in the order of 9-10 minutes, and the tops weren't bubbling (hence my impression the oven was quite cool). Still - got a couple of nicer pies off the sillimanite block - with crispy non-folding bases. Overall - it performed a bit better than the skinny stone, but we need to try it in a better oven.

2) I Found and ordered a 12mm x 400mm x 400mm steel plate and will pick it up tomorrow afternoon. I'll throw some pies on it tomorrow evening & report back in due course.

To avoid getting OT - I've added to another thread on steel plates: http://www.pizzamaking.com/forum/index.php/topic,16519.0.html
« Last Edit: December 20, 2011, 05:24:39 AM by breadman_nz »

Offline tinroofrusted

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Re: Sillimanite Kiln Shelf
« Reply #5 on: December 20, 2011, 02:01:21 PM »
Scott, what would you think of the conductive properties of 1/2 inch stainless steel with a diamond pattern on it?  I have a chance to buy a piece of this and wondered if you thought it might be better just to get plain metal.  Your advice on this would be great.  Thanks.

TinRoof

Offline tinroofrusted

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Re: Sillimanite Kiln Shelf
« Reply #6 on: December 20, 2011, 02:03:33 PM »
Scott, what would you think of the conductive properties of 1/2 inch stainless steel with a diamond pattern on it?  I have a chance to buy a piece of this and wondered if you thought it might be better just to get plain metal.  Your advice on this would be great.  Thanks.

Also, is there a certain grade of steel that I should look for?  Are there any types of steel that you would avoid?  

TinRoof

I quoted myself by mistake. Sorry! 
« Last Edit: December 20, 2011, 02:05:14 PM by tinroofrusted »

buceriasdon

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Re: Sillimanite Kiln Shelf
« Reply #7 on: December 20, 2011, 03:44:45 PM »
Actually carbon steel is better than stainless when it comes to conductivity. SS=16, carbon steel=43. Cast iron slightly higher than carbon steel. However metals such as copper and silver are near ten times more conductive with silver slightly edging out copper.
Don
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html


Scott, what would you think of the conductive properties of 1/2 inch stainless steel with a diamond pattern on it?  I have a chance to buy a piece of this and wondered if you thought it might be better just to get plain metal.  Your advice on this would be great.  Thanks.

TinRoof

Offline scott123

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Re: Sillimanite Kiln Shelf
« Reply #8 on: December 20, 2011, 05:16:57 PM »
Thanks for the advice so far!

Two updates:

1) We had a major pizza baking session this weekend, feeding about 30 people (24 pies in total). Two pizzaiolos (me and my brother). Had a simple, el-cheapo round stone on the top shelf, and the sillimanite block on the lower shelf. Didn't have an oven thermometer, but I'm not convinced the electric oven was very hot at all. The sillimamite shelf cooked well - but both top and bottom shelves were taking in the order of 9-10 minutes, and the tops weren't bubbling (hence my impression the oven was quite cool). Still - got a couple of nicer pies off the sillimanite block - with crispy non-folding bases. Overall - it performed a bit better than the skinny stone, but we need to try it in a better oven.

Breadman, for future reference, regardless of what kind of stone you're working with, you really can't bake with two stones at the same time in a home oven.  Beyond taking twice the pre-heat time to heat both stones, you can't use the broiler to bake the pizza on the bottom, and, in most non modded oven scenarios, you will want to incorporate the broiler.

Offline scott123

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Re: Sillimanite Kiln Shelf
« Reply #9 on: December 20, 2011, 05:24:22 PM »
Scott, what would you think of the conductive properties of 1/2 inch stainless steel with a diamond pattern on it?

Jim, as Don pointed out, it has half the conductivity of steel.  Soapstone clocks in at quite a bit lower, but, what soapstone (at least a good grade of soapstone) lacks in conductivity, it makes up, to an extent, in heat capacity.  Stainless gives you all the weight of steel (and it's heavy), with half the conductivity and the same heat capacity- at usually a few times the price. If you were getting this stainless plate for free, then it might be worth playing around with, but, when compared to regular steel, stainless loses in almost every area.


Offline tinroofrusted

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Re: Sillimanite Kiln Shelf
« Reply #10 on: December 20, 2011, 05:27:06 PM »
Thanks Scott. I'm glad I asked.  It's not free, so I will move on and look for carbon steel. 

Best regards,

TinRoof

Offline breadman_nz

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Re: Sillimanite Kiln Shelf
« Reply #11 on: January 01, 2012, 05:00:46 PM »
The sillimanite chemical formula is Al2SiO5, according to wiki, which is different from cordierite ((Mg,Fe)2Al4Si5O18).

Of course it's more than the formula which determines baking stone performance. I don't have access to any of the other details (density, porosity etc) of this particular shelf to more objectively determine its likely characteristics in the oven.