Heat treating in roaster.

[Allyn T]

I recently tried this for my first time and it ended up not being a success. What I think I learned is first sucky rock will stay sucky, this mostly has to to with chalky layers in the stone. So I think it helps tough poor rock become better, it can't fix what isn't there to begin with. The second thing I learned is the stuff on the bottom gets the hottest so that's where the biggest stones should go so they can soak. I had no breakage and a few pieces did improve enough to use but most did not.

[bjrogg]

I have played around very little.

I know some you can get to hot and make it brittle.

Some you can’t get hot enough.

And some like Goldilocks is just right.

I have some local stuff I want to cook under a bonfire when my cousin comes to visit this summer.
I’ve never been able to get it hot enough to improve it much in a roaster. Not sure I can under a bonfire,  but it’ll be fun to give it a try.

Bjrogg

[Allyn T]

I would like to try a bonfire cook too if I had the room. I've already cooked the second batch of Burlington It was better rock and I soaked it for longer I've only taken out one piece but it is like butter. It turned out very nice

[bjrogg]

That’s great.

Looking forward to seeing what the future brings.

Bjrogg

[RickB]

Allyn, I heat treated some slabs recently and put this info together. Hope you don't mind me putting it in your thread but maybe
it will have something of value. RickB

I heat treat some rock as it can improve the workability and sometimes enhance the color. This
does not work or is needed for all rock. An internet search can provide you some temperature ranges that different
types of rock will need. The roaster that I used was bought at a local flea market for $10. This is an older model
and the temperature on the dial goes up to 500°F. With the ceramic liner taken out, I have gotten temperatures up
to 650°F

Wife and I went camping a couple weeks ago and I used the campground's electricity to power an old
turkey roaster for a couple days. To get higher temperatures, I removed the ceramic liner in the roaster.
You will see in the photos below that I have drilled two holes into the top of the roaster lid. One is in the
center and one is in a corner. There are 4 heating elements in a roaster, one in each of the corners. That
is where the higher temperatures are attained. I put a high temperature BBQ thermometer in each hole to
get accurate temps as the dial will be inaccurate when the liner is taken out. I have a five gallon bucket
of clean playground sand that I keep using over and over for heat treating. I placed the trimmed mookaite slabs
along with some Florida coral and a piece of Brazilian agate into the corners of the roaster with some sand
to hold them in place. When all the pieces were added, I then filled up the roaster with the rest of the sand.
The sand helps retain the heat and keep it at a constant temperature.

I had to constantly check the temps out as I slowly raised it to 200°F/250°F for at least a couple hours. This
drives out any moisture that could crack the rock. After that, I slowly ramped the temp 50 degrees per hour until
it got to 450°. I ended up keeping it at the higher temp for about six hours and turned the power off to let it
slowly cool. When it got down to 100°F I took out all the pieces and randomly pressure flaked some of them
to see if I could pull a nice flake off. All pieces flaked good enough for me to work but I selected several to put
back into the oven at 500°. I wanted to see if the higher temperature helped get the rock any better. I did
not see  much difference at all so that was it. Photos below show three pieces that I tested. I just flaked one
of the sides and not both. I did end up making one point out of the mookaite. Nice, thin, good color and
light gloss. In the Southeast we would call this point a Morrow Mountain.

Raw slabs


Trimmed preforms


Two photos of the roaster oven




Heated slabs


The same slabs, flaked on one side


Test flake running across the top edge


Arrowhead

[Allyn T]

Man that is beautiful stone! Im really glad you posted, we need more info on poor man's heat treating for sure. Do you insulate the lid of your roster? I need to test mine and see what temps I'm getting. Mine goes to 450, I used no sand and I cooked for 24 hours this time. I used a drying temp of 175 for 11 hours first then I turned it straight to 450. When it was done I turned it all the way down and unplugged it. Opened it about 10 hrs later. No pops or broken rock inside.

[RickB]

Thanks, glad to help and others may have additional info to chip in. I do not insulate the lid but I know that many others do.
This mookaite is pretty expensive material from Australia and I've picked up a piece or two at various gem and mineral
shows in North Carolina through the years. Finally was able to get someone to slab some and then I did the trim work. It has
so many fissures that it has to be trimmed along the cracks to get fairly clean pieces that are knappable. I have heat treated
chert spals basically the same way as I did these slabs. Soak time in the heat is longer when heating thicker pieces. Check out
temps and heating times for different rocks on the internet.

Here's a ten year old post from archaeologist/flint knapper Michael Miller that has great information.

[bjrogg]

Thanks for sharing Rick

That’s some pretty stuff.

Bjrogg

[gutpile]

When cooking rock under a fire best be sure you have no rain in forecast or you will lose that stone.. I've never cooked any rock yet .. when I buy it it is already treated..no rock around me but quartz and you got to find the right quartz too.. most milky or real translucent is only knappable stuff around me.. so I have to buy or barter my rock..  I watched full circle by thad beckum.. he cooks rock under a fire with great success.. lines the rock in a sand bed and covers it.. really cool stuff to watch it change colors and upgrade the lithics of the stone.. early man were badasses.... gut

[Allyn T]

Yes early man really set the stage for the rest of us. D.C. Waldorf in his book uses a kiln and the temps he gave for material around me were 550-600 for harvest, and 600-675 for Burlington. With him doing it in a kiln it really isn't applicable to what I do but I'm trying to base my longer cook times off of his temperatures. I really need to get a thermometer in my roaster to see what it is getting too. I hope people keep posting their turkey roaster rock recipes and their results I think it would be beneficial to all of us. I'm going to try to heat treat some harvester just to see what it does. I'm just glad I don't have to heat agatized coral or novaculite, those require some ridiculously high temps.

[Allyn T]

So my second batch was a better success. The chalky rock still didn't improve just color changed but the good Burlington got slick and is a pure white except for the fossils. Some of the crystal looking blue grey Burlington turned a pinkish purple and it's workability improved a lot! I'll post some pictures later. Here is one of the fossil pieces though.

[gutpile]

bad ass.. gut

[bjrogg]

I somehow missed the last picture Allyn. I would have to agree with gut. Bad ass

Bjrogg

[Allyn T]

It is pretty cool. I really like the fossils

[Allyn T]

I checked my roaster last night. With the insert taken out and lid insulated it still only got up to 450 which is the max temp on the dial