Heat Treating Chert in a Turkey Roaster Video

[Dalton Knapper]

Most folks already know how to heat treat rock in a turkey roaster, but I saw a need for a good video of that and posted one to You Tube. I hope some people can benefit from it. In this video, I heat treat some Crowley's Ridge Chert  AKA Lafayette Formation Gravels/Chert. It's a crazy rock because there are dozens of kinds of rock together called "Crowley's Ridge," but it varies from agates to misc. cherts to Burlington. I am finally figuring out which ones need higher temps and which ones need lower temps by the way they look. Regardless, this video should be helpful to anyone who wants to heat treat rock in a turkey roaster. Enjoy - Ben

http://www.youtube.com/watch?v=qQ5r6ejiZrM

[JackCrafty]

Cool.  Can never have too many heat treating vids.   

I don't use sand in mine but I insulate the lid and throw a canvas cloth over the top for the cool-down.

[Dalton Knapper]

I have thought of using foil-backed insulation before and would probably use it in winter since all but the lid of a roaster is insulated anyway. One reason I dome the sand is to add as much mass to the process as possible and reduce temperature fluctuations. Bottom line is that there is more than one way to heat treat a rock. I am curious however about your method. I am sure the heat transfer with insulation must be good. How full do you pack your roaster? Do you put the insulation inside or outside the lid? If it works, it works and I am absolutely sure you know what you are doing. There is more than one way to heat treat a rock!

[JackCrafty]

Yes, there is more than one way to heat treat stone.

I insulate the inside of the lid with fiberglass and cover it with heavy duty aluminum foil.  I wrap the foil up and over the rim of the lid and it keeps the insulation in place.  This interferes with the seal of the lid, so I drape a canvas cloth over the oven to keep out drafts.  I use plain old fiberglass insulation for the lid. Because of the out-gassing issue, I used to keep the oven outdoors but the moisture (dew and rain) causes shorts and burn-outs in the control wiring (behind the temperature dial).  I now keep the oven inside the ventilated area of my shop.

I don't worry how much stone goes into the roaster but I usually fill it at least 1/3 full.  I've heated single large chunks before without any issues.

The guys that I know that have the fancy, expensive kilns never use sand so I've never used it either.

[Dalton Knapper]

I may have to try that. The contacts on my roaster keep getting rusted. I don't have any other place to roast, but I think I will start taking it into the garage when the roaster is not is use. Thanks for that tip. I don't want mine to burn out.

[knapperhead]

Thanks for the video, some of the Texas stuff I've been cooking needs to go a little longer. I may fire up the lighter colored stuff again and let it cook for about 24 hrs this time.

[Dalton Knapper]

I had some lighter colored and more coarse Edwards that was so tough the shock hurt my hand to hold it when doing percussion work. After heat treating it for 48 hours at about 500, I have to tell you that it is now one of my favorite rocks to knap.

24 hours would probably do, but you might consider a longer "soak."

Glad you liked the video and good luck.

[knapperhead]

Thanks for the reply, your'e not kidding about the hand shock. It should be ok to re-cook them huh?

[Dalton Knapper]

If it never achieved good heat treatment, it certainly won't hurt anything to try and heat treat it again. Just make sure you don't over do it and burn everything up. Re cook it for sure.

[knapperhead]

Just an update: I re-cooked it at 200 for 4 hrs and the 400 for 24 hrs. This time it brought out a lot of bands and some nice red colors. Most of it is slick now and makes a nice crisp crack sound when flaked. I only had time to take a few test flakes but hope to turn it all to rubble some time next week. Thanks for all the advice......