Any Experience With Corderite?

[skan]

In preparation for using the cordierite shelf for baking a pizza on tomorrow, I carbonized the bottom by mopping it with sugar-water and heating it in the oven at 600°F for about an hour.  This is to darken it for more rapid radiant heat absorption.  I will likely sugar-heat treat it a few more times before all is said and done.  I will only treat the shelf this way on the bottom, as I want the top to remain as reflective as possible to benefit the rim of the crust not in direct contact with the shelf.  Attached is an image of the contrast resulting from the first treatment.

- red.november

Hello

It would be nice to have an accurate measure of the temperatures on the black coated face and on the other one.
You want the top face white because you think it will reflect heat.
But other factors need to be considered.
Most of the heat could be transfered by convection or conduction.
If the face is black it could also absorb more (heating more the stone) and irradiate more, depending on its temperature, or more precisely it will irradiate at a different wavelength.
To summarize we need to know what's more important, reflectivity or emisivity.

[PizzaEater101]

I just thought I would throw up an image or two of a pizza I baked tonight on the cordierite shelf.  I have been baking on this shelf constantly since September 11, but I haven't stopped to take pictures of the products until tonight.  Even tonight's picture taking was totally unplanned, so the images aren't really all that great due to a rushed setup.  The pizza however was great.  It simply had mozzarella cheese and baby portobello mushrooms (no sauce).

- red.november

I know this is an old post, really old post but I love that spider web effect in the rim.  Always love spider webbed effect in pizza rims.  I know this is an old post but do you know what dough formulation you used?


Thanks

[November]

It would be nice to have an accurate measure of the temperatures on the black coated face and on the other one.
You want the top face white because you think it will reflect heat.
But other factors need to be considered.
Most of the heat could be transfered by convection or conduction.
If the face is black it could also absorb more (heating more the stone) and irradiate more, depending on its temperature, or more precisely it will irradiate at a different wavelength.
To summarize we need to know what's more important, reflectivity or emisivity.

Firstly, if you look through more of my posts you will notice I have talked quite a bit about carbonizing or seasoning the top.  It was in this particular case I only wanted to carbonize the bottom.  Secondly, there is no question that a darker surface will absorb heat more rapidly than a white or reflective surface, so I'm not sure why it matters what the temperatures are.  Also, simply saying "temperature measurement" doesn't mean much anyway.  Measured how, IR thermometer or thermistor?  An IR thermometer will only measure radiation, and a thermistor will only measure conduction (assuming a silvery metallic probe).

Other factors need to be considered, indeed.  Here are two of them.  Metal conducts heat better than air or stone/ceramic, and a broiler element gets exponentially hotter than the stone.  So if you aren't preheating your stone with a broiler element, and you aren't planning to preheat very long, or you use the broiler element during the bake, the top of your oven will be much hotter than the top of your stone.  Depending on the preheat time and where the stone is placed, there is great potential for more thermal energy reaching the top of the stone via radiation from the top of the oven than from the stone itself.  If you question this, just look at the top of your crust sometime.  All that browning is a result involving convection and radiation; not conduction.  Now look at the pockets that form on the bottom of the crust during baking, and take note of how pale they are.  The surface of those pockets are only millimeters away from the stone surface.  You have to realize that the pizza itself is a big heat sink.  It's drawing so much energy from the stone via conduction, that the emission of radiation is diminished.  So when you compare radiation from the stone versus radiation from a broiler element or preheated metal surface, the stone loses almost every time.

or more precisely it will irradiate at a different wavelength.

Wavelength and temperature are not related in the manner you suggest.  Bodies emit radiation over a broad range of wavelengths.  To understand the full relationship, read about the Stefan-Boltzmann Law and spectral radiancy.  However, carbon is the main actor in all oven radiation no matter what surface we're talking about, so spectral radiancy is unlikely to change significantly in any case.

- red.november

[November]

I know this is an old post but do you know what dough formulation you used?

I can't be 100% certain, but this was the last formula I posted before getting the shelf:

http://www.pizzamaking.com/forum/index.php/topic,1014.msg46728.html#msg46728

It's likely to be some variation of that formula, such as with or without malted milk.

[TXCraig1]

If the face is black it could also absorb more (heating more the stone) and irradiate more, depending on its temperature, or more precisely it will irradiate at a different wavelength.

If you're curious, a while back, I wrote a couple posts that discussed the relationship between temperature, wavelength, and radiance:
http://www.pizzamaking.com/forum/index.php/topic,18573.msg180727.html#msg180727

CL

[bfguilford]

After experimenting with 1/2-inch steel plate, and stopping because the weight of it was too heavy for my back, I am now wondering if a high alumina kiln shelf would be a better option for quicker heat transfer than a regular cordierite shelf. I have located 3/4" thick high alumina shelves (claimed to have 11-12% more alumina content).

Oven setup is electric oven that goes to 550 degrees, with a broiler that will remain on even at that temperature. Not a true convection oven, but a small fan on the back wall. I'm also thinking of using a soft firebrick drilled out to fit over my thermostat to get it up to 600-625.

Barry