Heat treating rock?

[Lobo69ss]

Greetings Gents &/or Ladies...  Having gotten a nice turkey roaster to play with I`m about to try my first load of stone cooking... is there a "Rock Cooking for Idiots" book I can get to attempt to learn this new skill?  I don`t have a lot of stone to play with & most  that I do have I have NO idea if/or how heat treating will affect the rock...
  I was gifted a couple slabs (1/4") of Louisiana Carnelian & some of Agate (of unknown variety Grey/white w/inclusions) ... Any hints as to a possible temp/time frame which might make these pieces more workable? I`ve also got some Texas flint (Lano)...
  I`m aware that I`ll be heating to around 200 or so for several hrs. drying time... Any suggestions as to a starting point for ramping up the temp. & hold time?  As I said, this cooker is new in the box, I won`t be using the inner pan, just sand on the bottom, layering slabs alternating w/ more sand .... Where do I go from there please?         Thanks in advance for any/all help

[cowboy]

Hey Lobo, it's pretty straight forward process.. The darker the rock the less heat it'll need if any, lighter colored stuff will need to go to max in my experience.
 Load your roaster and try to keep the pieces no thicker than say 1 1/2" or thinner. The corners of the cooker seems to get the hottest so place your thinner/lighter colored stuff there. I don't even use sand, just load it up full.. Dry them at 200 for a day, start ramping up around 50 degrees every several hours or so till your at max, let soak at max for around a day then ramp down the same way, turn off unplug whatever after its been at 200 for a couple hours, pull your rocks out after they've cooled for awhile couple hours or less probably. Voila! their either perfectly treated, didn't quite get enough or have blown up, ha... You'll probably have a mix of all that depending on type of rocks.. Good luck!

[Dalton Knapper]

I take a slightly different approach and you can watch my video here: https://www.youtube.com/watch?v=qQ5r6ejiZrM

Be aware that if you take Cowboy's approach, and there is nothing wrong with that, be sure and ramp up and down because the mass of the sand acts as a buffer against rapid temperature changes and if there is no sand, it is possible you could crack rock if it heats up or cools down too rapidly - hence the need for ramping if there is no sand. I think it helps distribute the heat better, but then again, what works.....works.

[knapperboy]

Hey Lobo, these guys have pretty much summed it up. But here is what I do if it helps any at all. I cut my blanks on a wet saw or billet them out roughly before baking. I then sandwich my blanks in between layers of sand to keep the blanks at an even temperature. Then (depending on how hot the bake needs to get) I start to work my way up to the heat I need, then I evenly start to decrease my temperature back down to zero. Be sure to give your stone enough time to cool and don't be too hasty about things. Pretty soon you'll learn what works and what doesn't. As far as rock itself goes, it's somewhat individual. Different rocks will need a higher heat (hot bake) and others not so much (cool bake). Allow yourself some room for mistakes and learn from your experiences. That's all there is to it! Hope that helps
                                       KB

[JackCrafty]

After heating literally a ton of rock, I just throw it all in (chunks, small flakes, and whatever) and never use sand.  Sometimes I only heat one piece.  I heat it @ 200-250 for a day to dry it out, crank it up to 400-450 degrees all at once and let it stand for 4 to 6 hours, then turn it off and let it sit for 12 full hours before I open the lid.  I throw a piece of canvas over the top of the oven to keep out drafts during the whole process.

Make sure you insulate the lid.  I use regular R-13 fiberglass insulation and heavy duty aluminum foil to hold it in place.

My way is the lazy way and it works for me.   Cowboy's method is what I used in the beginning and got excellent results. 

Good video, Ben!