Heat treating with Kamado grill?

azmdted
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azmdted
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September 5th, 2018, 4:56 pm #1

Hi all,

I've recently picked up some Flint Ridge material that is harder than anything I've wacked yet.  Time to experiment with heat treating.  I've read all I can about Turkey Roasters.  While I wait for turkey season to come around, I 'm thinking of using my Kamado Joe (like a Big Green Egg), ceramic grill to heat treat.  I can put enough lump charcoal in it to run 12 hours at 250 and then bring it up to 550 for another 10 hours or so.  I'm thinking of using the heat deflector that is used to diffuse the heat when smoking, and an extra pizza stone to further avoid direct heat and then just putting the rocks in a roasting pan on top of that.

Anyone ever tried that, or see any serious issues?

I thought of posting this on the Kamadoguru.com cooking site, but I don't think many of them intentionally cook rocks.

Thanks
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azmdted
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azmdted
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September 6th, 2018, 12:24 pm #2

Using the old scientific adage of 'what the heck', I plunged in and started my kamado heat treating. It's been at 250 for the last 15 hours. I will be slowing raising it to 500-550 today and probably let it stay there tonight, we will see.
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freeze cracked
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freeze cracked
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September 6th, 2018, 1:30 pm #3

the specific "recipes" online for how to heat rocks are followed because of lots of failures during heating with different protocols. many people have lost big loads of rock that they had a lot of time and effort in. 

i would follow the recipes, particularly as they relate to initially holding the temperature at least slightly under the boiling temperature of water, to allow all moisture in the stone to exit in an orderly fashion without fracturing the material. ridge material is very dense, and so the moisture in it got in very slowly and needs to come out very slowly.

when you heat rock too rapidly and/or overheat it, you will probably end up with potlids and/or aquarium gravel.
i dream of a better world in which chickens can cross roads without having their motives questioned.
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azmdted
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September 6th, 2018, 1:37 pm #4

Thanks Freeze, I understand.  I'm sure that many recipes don't fully explain their initial conditions as well, e.g., how long the rock has been out of the ground and drying before heat treatment.  The 'recipe' I chose to follow is what Roy Miller discussed in his  videos on heat treating Flint Ridge.  He said 5-10 hours at 250 then gradually increasing.  No doubt I will learn many lessons from this first batch.  I appreciate all input as I learn them.
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freeze cracked
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freeze cracked
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September 6th, 2018, 1:57 pm #5

the quality of material chosen and how thin it's blanked out prior to heating also matters a whole lot. roy is certainly an expert and i think many who've heated vast quantities of material have an intuitive understanding of what they can do without paying any big price. 

i think the guidance at this link is also relevant info i would have under consideration were i to do much rock cooking. ==> this link
i dream of a better world in which chickens can cross roads without having their motives questioned.
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azmdted
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September 6th, 2018, 2:29 pm #6

Thanks again, I studied that page last night.  I noticed the 205 v 250 degrees and hoped that the 250 was something best for the nature of Flint Ridge.  I only have about 15 pounds in the pan with another 75 or so left.  Worst case is I make another run to the Ridge when the weather is cooler and drier.  BTW, I was going to try the Turkey Roaster method but both local Walmarts didn't have any in stock.  I'm guessing it's largely seasonal and I won't see any for another month.  I also have to get better at spalling this stuff.  Given the nature of the material I found (about 1.75" thick sheets between cracks) I had a heck of a time trying to spall it raw.  More lessons to learn.
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freeze cracked
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freeze cracked
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September 6th, 2018, 2:39 pm #7

there are other materials that are considerably more user friendly
i dream of a better world in which chickens can cross roads without having their motives questioned.
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azmdted
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September 6th, 2018, 10:43 pm #8

Update:  I heated up the rock to 370 after about 17 hours between 200 and 250, then a slow rise up. It peaked at 370 after 22 hours when it seems to have used up all the charcoal. It is slowly dropping temp now. This is okay as it fits in with the link that Freeze cites above. This weekend I will start flaking the pieces and see which ones need to go back in for heating up to 500.  Hopefully the larger pieces will also spall better now. 

On a separate note, we are heading to the Meadowcroft Rock Shelter tomorrow for a tour led by Dr. Adovasio on Saturday. I’m looking forward to it. 
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WIoutdoorguy
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September 7th, 2018, 12:23 am #9

Azmdted,
If you have a local thrift store or Goodwill you may be able to get a used turkey roaster for cheap.
Lucky you on the tour of the Meadowcroft Rock Shelter. That would be a great experience, even better with Dr. Adovasio as a tour guide.
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azmdted
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September 7th, 2018, 1:32 am #10

WIoutdoorguy wrote: Azmdted,
If you have a local thrift store or Goodwill you may be able to get a used turkey roaster for cheap.
Lucky you on the tour of the Meadowcroft Rock Shelter. That would be a great experience, even better with Dr. Adovasio as a tour guide.
Thanks, good idea. We’ve got a couple Goodwills here. I will check them out. First though I need to see how this batch turned out. Fingers are crossed. 
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PaleoSoul
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September 10th, 2018, 12:38 pm #11

No sure if this was covered but I'd use some sort of medium such as sand to help hold the temps. I rarely just put rock in the oven unless it's a kiln.

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azmdted
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azmdted
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September 10th, 2018, 12:46 pm #12

PaleoSoul wrote: No sure if this was covered but I'd use some sort of medium such as sand to help hold the temps. I rarely just put rock in the oven unless it's a kiln.

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Thanks, while I didn't use sand, the Kamado Joe grill has an inch and half of ceramic surrounding it which holds the heat in.  Probably not as well as a kiln, but infinitely better than a typical sheet metal grill.  It can take about 6 hours to get back to air temp following a cook.  Nonetheless, I'm going to head out to a Goodwill today and see if I can find an old turkey roaster and I will definitely use sand in it.
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Bill Skinner
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September 15th, 2018, 12:59 am #13

The sand is to keep the heat even on the rock.  If one side is hotter than the other, that will cause the rock to heat faster on one side than the other and that can cause the rock to crack.  Specifically, the bottom of the rock heats up faster than the top when it is over coals.

EDIT:  You don't need an actual turkey basting pan, just a metal pan with a lid to hold the sand.  And if you are careful, you don't actually need a lid.  The lid is there to catch sand and fragments if a rock explodes inside your oven.
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