Author Topic: Central Texas Chert?  (Read 5396 times)

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Offline paulc

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Central Texas Chert?
« on: November 26, 2016, 11:50:30 am »
All, I bought a box of above stone more than 1 yrs ago. Just now getting around to trying to work it. I bet this is too little info but should I cook it first?  And how?

Thanks, I can try to get some pics if that would help.

Paul

Offline Chippintuff

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Re: Central Texas Chert?
« Reply #1 on: November 26, 2016, 12:33:34 pm »
Pictures would help a lot. A lot of the Central TX rock is ready to chip when it comes out of the ground, but some needs to be cooked. Don't cook it till you get some input, because even if it needs some heat, the heat needs to be just right. Too much heat and it fractures to pieces.

WA

Offline Zuma

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Re: Central Texas Chert?
« Reply #2 on: November 26, 2016, 11:43:54 pm »
This was exposed and not down in the sand
at 500 degrees a tad to warm.
Zuma
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Offline Outbackbob48

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Re: Central Texas Chert?
« Reply #3 on: November 27, 2016, 08:26:34 am »
ooooh, potlids :o :o :(

Online bjrogg

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Re: Central Texas Chert?
« Reply #4 on: November 27, 2016, 09:17:34 am »
My brother had some that I cooked in turkey roaster. I over cooked it and ruined about half of it. It became really brittle. I didn't realize at the time that I could even over cook any stone in turkey roaster. Now I try to get more info and try small amount with more conservative temp and soak time 1st then if that's not enough get a little more aggressive till I get results I want. I believe some of the Texas stuff is quite a low temp I think if my memory serves me right some as low as 350 degrees. I haven't cooked a lot of stone.  I'm sure many more experienced "chiefs" on here than me. I have had some excellent results but I did over cook some Texas stone. If it's not cooked enough you can always recook it more aggressive. If you over cook it it's ruined
Bjrogg
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Offline paulc

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Re: Central Texas Chert?
« Reply #5 on: November 28, 2016, 12:44:39 pm »
So here is one pic of the stones I have to work with.  I hit one with a hammer stone several times and ended up chipping the hammer stone and the chert broke into 3 random pieces...didn't seem to follow any kind of pattern.  I will try to get a pic of pieces up too.

Thanks, for the help

Stringman

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Re: Central Texas Chert?
« Reply #6 on: November 28, 2016, 02:39:02 pm »
Needs heat

Online bjrogg

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Re: Central Texas Chert?
« Reply #7 on: November 28, 2016, 03:10:03 pm »
I'm sure Scott knows way better than me. I agree it doesn't look real smooth. I might be workable but it looks like heat would help it. Now you have to figure out how much heat and I'm thinking you might have to get your pieces thinner too. Hopefully someone will jump in here and give you a recipe
Bjrogg
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Offline Tower

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Re: Central Texas Chert?
« Reply #8 on: November 28, 2016, 08:13:11 pm »
When I heat cobbles of flint like that  I keep it at 210* for 24 hrs to reduce moisture. After the that I take it up  50* ever 4  hrs to 375*.   I hold it at the final temp for 8 hours then I unplug & let cool
Most TX stone doesn't need much heat. That should turn it into candy.
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Offline Chippintuff

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Re: Central Texas Chert?
« Reply #9 on: November 28, 2016, 11:05:37 pm »
I have chipped a lot of stuff that looked like that. It needs to be sawn or bifaced before cooking, else it will most likely blow up. I agree that it needs a preheat temp of 190-210 degrees F before beginning to ramp up. I think it will take 500 degrees to get very agreeable. Hold it there for 3-4 hrs or a whole day before ramping down.

Instead of ramping, I put sand under, around, between and over the rocks when placing them into the cooker. The sand is excellent for ramping the temp down for me. In other words, after cooking at the top temp, I just turn it off and the sand prevents any fast ramp down. It usually takes at least 16 hrs before I can touch the rocks.

To do the cooking, buy a turkey roaster for $25 at Walmart. Take the liner out. Drill holes into the lid at various places to allow insertion of a meat thermometer. Wire some fiberglass insulation to the inside of the top cover. When loading the cooker, keep in mind that around three sides (not the side with the regulator) the temp will be 50 or more degrees above the temp of the rest of the inside. Put the toughest stuff there. Do NOT depend on the temps printed on the control dial. Insert a meat thermometer. Be sure it is a thermometer that can go to your target temps. Do not open after starting the cook until the temp is down to 120F or lower, else the rocks may fracture when fresh air hits them. If they have been sawn, be sure to soak them in soapy water for a few hours or overnight then wash them thoroughly.

If the rocks were recently wet, be extra careful that the preheat at below boiling temps is adequate to dry the rocks thoroughly.

PM sent.

WA
« Last Edit: November 28, 2016, 11:16:23 pm by Chippintuff »

Offline paulc

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Re: Central Texas Chert?
« Reply #10 on: November 28, 2016, 11:10:52 pm »
Thanks Tower!

Paul

Offline mullet

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Re: Central Texas Chert?
« Reply #11 on: November 29, 2016, 08:47:43 pm »
I've destroyed some at 450-500 degrees for 24 hours. I will bring it up slow to 350, about 2 hours, then up to 400 for another 5 hours then turn the kiln off and let cool down till I get home from work the next day. A kiln holds heat for a long time.
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Offline paulc

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Re: Central Texas Chert?
« Reply #12 on: November 29, 2016, 11:09:38 pm »
Thanks so much everyone!  I might be able to pick up some flint Ridge, OH stuff over winter holiday. Hopefully the weather won't be too miserable...

Paul