Over cooked stone?

[paulc]

Is this what over cooked stone looks like?

Too hot? Or too long? Crappy stone? Thanks for your thoughts?

Paul

[bjrogg]

It could be. I’m not sure. Is that what it looks it when you try to flake it.

If you overcook it it becomes very brittle. It just kinda crumbles when you hit it. Breaks instead of flakes
At least that’s what happened to the stuff I overcooked.
Bjrogg

[JEB]

That looks like crappy cracked up Texas rock to me. I bring home a couple 5 gallon buckets of the stuff after the winter months out west and maybe I get a 1/2 a 5 gallon bucket of good stuff.

[paulc]

JEB, it is Texas rock. I had purchased perhaps 8 or 10 stone in a box from an online vendor. Probably 3/4 looked like this after cooking. It just crumbles and fractures randomly when  hit....it is nice and waxy but crazed and I can do zip with it. Maybe if I had cooked it less BJ it would flake proper?

Paul

[JackCrafty]

Yes, that's one type of heat treating fail.

The heat was probably too high. A lot of TX rock, especially the darker colors and translucent stuff, needs only slight heat. Some as low as 275 F. I usually test a few spalls at 300 F. That way, I don't lose too much stone in the test phase.

The stone doesn't look crappy. Did you try to knap some raw?

"Too long" is usually not a thing. Stone can stay hot for days without problems.

[paulc]

Thanks Patrick, I did try some raw and it refused to break...maybe I should try another box and keep the temp down....

Paul

[JEB]

Not sure who you are getting your Texas rock from but give Curtis Smith a call. He shows up at a few of the knap ins that I go to and I have seen his Texas rock and it looks pretty good.  If you order from the same guy you may be getting that same rock .  All Texas rock ain't equal.  I gather it up from a 60 mile radius and some looks like the stuff you have after a heat treat and others butters up real nice. Patrick has a heat treating chart at the bottom of his posts. Follow that as he knows what he is doing.