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Would a pizza stone assembled from multiple pieces be smart/useful?

I have access to an old marble quarry, and I would like to go cut a stone there. It seems too complicated to cut a huge piece (even more considering I need to sand it and all) so I wondered if I could instead cut "bricks" that would be easier to handle (and even to store). For example, 20 centimeter pieces I could assemble depending on the size of the pizza and when I'm done put it away.

Has someone ever attempted this? Or is there some fundamental rule that would ruin my plans? I expect to have something less performant, but not too much

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Orsu
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    I realize you already accepted an answer, but please see the comments below about the inadvisability of using marble. – FuzzyChef Sep 01 '21 at 18:15
  • Homogenous stone like Graywacke or Granite would be better options, as long as you can dry them initially. Can you get either of them ? – Criggie Sep 02 '21 at 04:34
  • @FuzzyChef yes thank you! @\Criggie granite very probably, but now i realize that DIY stone extraction is probably way too complicated for now real ROI. I'll stick to an unglazed tile, or a thick piece of metal if i find one – Orsu Sep 02 '21 at 07:07
  • Orsu: other stone would be fine -- granite is OK, I believe, and just about any igneous stone is good. But not marble or slate. – FuzzyChef Sep 03 '21 at 00:40
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    I use a cheap granite "chopping board" (a fine way to wreck your knives) that was also described as suitable for putting hot dishes on. I had to remove some rubbery feet from the back, which left it wet, so gave it a couple of hours in an oven at less than boiling point, before ramping up the temperature slowly - the drying isn't hard – Chris H Sep 03 '21 at 09:11
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    This isn't what you were asking, but I'd highly recommend baking pizza on a sheet of steel. Do a web search for "baking steel". – aswine Sep 03 '21 at 19:39
  • @aswine Yeah it does seem even better! I saw Mr Ragusa's video about it, but it's just more expensive to me. But one day... – Orsu Sep 03 '21 at 19:43
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    FWIW, a baking steel is just a sheet of 1/4" to 3/8" steel. If you have a scrapyard near you, and have time and access to a grinder, you can make your own for about 1/3 the price of a name-brand one. Personally, I prefer corderite ceramic. – FuzzyChef Sep 06 '21 at 04:36
  • @FuzzyChef There's no guarantee that some random piece of metal that you pulled out of a scrapyard hasn't been exposed to hazardous chemicals. I'm fairly confident that even paint might break down and release potentially hazardous chemicals in the heat of an oven. – nick012000 Sep 14 '21 at 07:19
  • Nick: that's why you grind & polish the whole surface, first. Generally you need to do that to remove rust, regardless. And you sure don't want painted steel. – FuzzyChef Sep 14 '21 at 18:12

2 Answers2

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Do not do this. Marble is, compared with ceramic brick or lava stones, extremely vulnerable to thermal shock. Your "bricks" will almost certainly crack within a few uses, and might even shatter dramatically.

FuzzyChef
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    The veins in marble are cracks of various degrees. A few likely to contain enough water to crack open , depending on heating rate and temperature. – blacksmith37 Sep 01 '21 at 21:03
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    Marble will also start to decompose slowly at pizza oven temperatures, breaking down into calcium and magnesium oxides (ie: lime) that become corrosive hydroxides when mixed with water. You definitely don't want that in your pizza!. – J... Sep 02 '21 at 13:24
  • @J... Depending on the quantities involved, wouldn't you just end up with something like a pretzel crust? :) – chepner Sep 02 '21 at 13:25
  • @chepner Sure, if you're in the habit of salting your pretzels with lye... ;) – J... Sep 02 '21 at 13:27
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    Not salting, but the dough is prepared by boiling it in a (weak) lye solution before baking. (OK, baking soda is probably more common, but it's pH that matters more than the particular base used.) – chepner Sep 02 '21 at 13:35
  • @chepner Fair enough, though it's really a weak solution. I'm not sure how long the marble would take to break down at only 480C, but it would be slow. Maybe it *would* make for something tasty... I'll let someone else make that gamble! – J... Sep 02 '21 at 14:59
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    FuzzyChef is right about danger -- Just get firebricks! They work great. https://www.homedepot.com/p/Rutland-4-5-in-x-9-in-x-1-25-in-Fire-Brick-6-per-Box-604/300980334 – rrauenza Sep 02 '21 at 20:27
  • I add about 40g of lye to a liter or so of water when making pretzels. I have no idea where that ratio came from, but it works well so I haven't tried to vary it. Without the lye bath they're just breadsticks. – GargantuChet Sep 02 '21 at 22:54
  • @rrauenza Are firebricks food-safe? Given you're putting the pizza directly on them? – Joe M Sep 02 '21 at 23:25
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    Joe: speaking as a potter: Maybe. It really depends on how they're made and what they're intended for. Firebricks made for ovens and for the hobby kiln industry have nothing in them but clay and stone, and are fine. But, industrial firebricks made for furnaces may have "clinkers" in them which can contain toxic minerals. – FuzzyChef Sep 03 '21 at 00:38
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America's Test Kitchen did tests of pizza stones, and one was actually a set of bricks. They found no problems from the seams ... which makes sense, considering that brick ovens would've been made from bricks, not large slabs of stone.

What I'd be concerned with is that you're talking about marble. It's not the most dense of stones, which means it won't hold heat as well as other stones, and it will absorb liquids. It also has veining, which are basically fault lines running through it. If you accidentally heat up a wet slab, you risk it cracking (possibly explosively, if you heat it up too quickly).

As such, you would want to heat it up to just below the boiling point of water, wait for it to dry out, and then crank the heat up on it.

Joe
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    Nitpick: from the figures I can find online, the specific heat of marble is pretty much the same as cordierite clay (which is what's usually used for "pizza stones"), and it's actually a bit more dense. So I'm skeptical that "it won't hold heat as well as other stones". – Michael Seifert Sep 02 '21 at 12:40