Heat treat fire experiment and your ideas

[iowabow]

I am goint to do a heat treating experiment. I will be recording data and detailing the findings on this post. Does anyone what input on the construction of the experiment before hand. For example " Could you record the rate of climb based on 2 inches of sand vs 1 inch". I have two pyromenters.

[JackCrafty]

Yes, all information is good...before or after!

[TRACY]

Yes, all information is good...before or after!

Ill second that


Tracy

[Will H]

Sounds cool John, Ive never tried the abo heat treating method. I know cowboy does it, maybe he'll chime in and give u some tips

[Tower]

I heated with a pit for several years, until I moved to New Braunfels. I prefered 2 to 3 inches of sand covering the pieces. Too little & pop. The heat will be too high.  I found the speed in which I brought the rocks to temp was the greatest factor. Small flakes & spalls can be heated rather quickly, but larger chuncks need a lot more time to reach the desired temp. I will add I prefer the color changes in abo heating to roaster. Lots of luck.  Tower

[iowabow]

Tower did you use a pyrometer "heat probe" during your firing? Not everyone has one so i was thinking i would  chart my data so people could have a base line to guess from.

[Tower]

I did use an old heat tec heater controller that had burnt contacts in it. The mercury indicator still worked. I used it to monitor the rise in heat. I would bring the temp up to 200 deg & hold it there for 3 to 4 hrs. Then I'd build a good bed of coals & let it cool down on its own. If the rock was REAL tough I'd put a little extra wood on it & call it a night. Thatmy method.

[cowboy]

I like 2 1/2 to 3 inches of sand all packed down good. Start a fire in the am, keep it going all day with about 4 to 6 inches of coals before bed. Don't have a clue what the temp was but was darn sure hot .

[jcinpc]

I cooked rock more than I cooked supper back in the day . I always put my spalls to the middle knuckle on my finger. I layered a good payer of charcoal and I sometimes would put a cooking therm. in it to see the temps. I didthis last week and had temps of 700 degrees near my thicker spalls and 500 by my candy pinhead coral.
The type of rock will also make a difference....also now that charcoal is hitting $8.50 a bag I am switching to wood

[mullet]

I've had good luck with about 3" of sand, big pieces on the bottom and smaller ones closer to the sand. Then a 20# bag of charcoal on top and let it go till it cools down. It works good this way for coral. Texas rock I've put a little more sand on top.

[iowabow]

Mullet this is a real cool thread and is a topic often on PA. Some of the best  knapper giving a advice on heat treating wow that is cool. I will keep a heat chart and take lots of photos during this firing. Maybe we can post this somewhere so new people can read it.

[mullet]

When it's done, John we can either pin it to the top here or move it to the Archives or Build along.

[iowabow]

Thats cool.
If anyone else wants to share your results please do. Pictures are welcome.

[RickB]

Here's a photo of my outdoor setup - it's a washtub and I call it my redneck grill, and you can see why from the first photo. I heat Savannah River Chert 3 to 4 inches down in the sand (each inch deeper equates to appx. 100 degrees cooler). Note: It is better to use clean sand and not dirt as you will get better heat conduction. 16lb bag of charcoal in the morning followed by another bag in the afternoon. Rock is finally cool enough to handle and comes out late afternoon of the third day. I use a piece of roofing tin to protect from wind and rain. Second photo is some chert and debitage along the front side of my shed. I'm currently using a turkey roaster, liner out, with clean sand (filled to the top). I put it on 250 degrees for a couple hours then turn it up to 450 - at 250, I've had steam condensing under the lid and sizzle when it falls back onto the hot sand. I now crack the lid a little to let it out when at 250. Thermometer I stick in shows hotter temps in the corners, cooler temps in the center. I put thicker and rougher pieces in the corners, thinner pieces everywhere else. I let it go for about 48 hours before I turn the heat off. Have had good result this way. Every time I look at this first photo I start getting hungry. Rick B