Heat Treating - The Light Bulb Turned On! (Updated 6-15-2011)

[JustinNC]

I'd heat treat that gray Ryolite. I'd be more fun watching it blow up than beating on it.

I think that's about the only way to get this crap to break.

See Eddie...i aint the only steewpud, desperate soul in NC

Although I'm somewhat proud of myself for carrying that 100 lb. rock out of there, I keep wondering just why in the hell I did that.

Yeah yeah yeah....coulda just took a big arse bag and carried it out on your back.

After seeing that photo I showed you today...there IS hope in that junk.

[jonathan creason]

I'd heat treat that gray Ryolite. I'd be more fun watching it blow up than beating on it.

I think that's about the only way to get this crap to break.

See Eddie...i aint the only steewpud, desperate soul in NC

Although I'm somewhat proud of myself for carrying that 100 lb. rock out of there, I keep wondering just why in the hell I did that.

Yeah yeah yeah....coulda just took a big arse bag and carried it out on your back.

After seeing that photo I showed you today...there IS hope in that junk.

Oh, I think the rock has potential, just don't think I do.

[JustinNC]

I'd heat treat that gray Ryolite. I'd be more fun watching it blow up than beating on it.

I think that's about the only way to get this crap to break.

See Eddie...i aint the only steewpud, desperate soul in NC

Although I'm somewhat proud of myself for carrying that 100 lb. rock out of there, I keep wondering just why in the hell I did that.

Yeah yeah yeah....coulda just took a big arse bag and carried it out on your back.

After seeing that photo I showed you today...there IS hope in that junk.

Oh, I think the rock has potential, just don't think I do.

Yep. You gotta be a special kinda stupid to break it just right.

[Ncsnipe]

Aw come on now, rhyolite ain't that bad. Just because it goes from bad to good side to side and front to back and has funky folds in the way the grain runs. Well maybe you guys are right come to think of it. You know it just makes it more satisfying when you do make something out of it.

[mullet]

It'd only take a ten pound bag of charcoal to find out.

[Tower]

I've a lot of grey from Richland springs Tx. Like that. Tough grainy but it knaps good when treated. Stays a little grainy but has the gloss and knaps good. Not my favorite Tx. Rock but It works.

[JackCrafty]

Richland Springs?  Never been there but looks like nice country.  I think the rock I have came from the San Angelo area.  Most of the grey I have knaps fine raw but the grainy stuff cooks well.  REALLY well.  I've narrowed down the possible rock types and I should know after this weekend.

[JackCrafty]

Well, figuring out what rock cooks best at what temperature is not as easy as it sounds... good grief!  I'm sure all you rock chefs know what I'm just now discovering.  Rock is not a consistent material.  Even though I've narrowed down the types of rock that heat well, the batches I'm cooking are all slightly different.  Sometimes the good stuff will blow up and sometimes the stuff I think won't heat well turns out fantastic.

 

[criveraville]

Sounds like you got a rock oven full of conundrums

[JackCrafty]

OK, the heat treating experiments are beginning to show fruitful results.

First, I will offer a link for you technical types:

http://www.latrobe.edu.au/geosci/Downloads/pdfs/John%20Webb_Jan%2009/Geoarchaeology/Domanski%20et%20al%201994.pdf

In this paper the change in various properties of the stone material tested is shown on graphs.  Certain materials do increase in elasticity while decreasing in fracture toughness (leading to fantastic flaking quality).

There are some materials in my "batch" that exhibit these changes and I am trying to isolate and identify them.  At this point, they seem to be cherts that are neither dark nor light in color.  The various medium "greys" and "tans", that are not glossy to begin with, seem to work best.

On page 202, the first two paragraphs mention a separate study that basically shows that heat treatment makes the structure of the stone more uniform and orderly.  This, in turn, allows the pathways of cracks to travel with less resistance.

Clear as mud?

Me take nap now.