Knapping Petrified Wood

**Erratus Animus** · 08-08-2010, 04:45 PM

Is there any preparation to knap Petrified Wood?

**Erratus Animus** · 08-08-2010, 06:52 PM

Ok I found out that it needs to be cooked at 300-450 degrees. So does anyone have experience knapping it?

**crashdive123** · 08-10-2010, 10:52 PM

I do not, but it sounds similar to coral. The coral I use has been baked at 450 to 500 for about 12 hours.

**Erratus Animus** · 08-10-2010, 11:04 PM

When you say coral are you talking about the reef pieces? I worked in a saltwater store for a couple of years and can get Tonga shelf coral pretty easily. Looks like a small board 1 1/4 thick and all coral. It is used in constructing the environment of the saltwater tank.

**crashdive123** · 08-11-2010, 07:22 AM

Originally Posted by Erratus Animus

When you say coral are you talking about the reef pieces? I worked in a saltwater store for a couple of years and can get Tonga shelf coral pretty easily. Looks like a small board 1 1/4 thick and all coral. It is used in constructing the environment of the saltwater tank.

I'm sure they were parts of reefs at one time or another. These pieces were gathered from the central part of the state, and probably have not been part of a reef for a few hundred thousand years or so.

**Erratus Animus** · 08-11-2010, 10:01 AM

I got ya. I should have known it would not be as easy as walking in the fish store and picking up a piece of coral

I see i am going to haft a search the net for the best price on Dacite to learn with

**ravenscar** · 11-05-2010, 06:40 AM

sorry for the bump but, how long do you cook petrified wood, and can i use my oven?

**canid** · 11-05-2010, 07:16 AM

yeah; the knappable coral is fossilized. i believe coral itself is mostly calium carbonate and fossilized coral is formed by mineral replacement mostly by silicates.

ravenscar: i've seen recommended between 300 and 450. when heat treating, increase the temp by 50 degrees per hour until you reach the desired temp, hold for two hours then kill the heat and allow to cool slowly.

not only is not all petrified wood suitable, i would say most that i've seen is not. make sure to select the stuff that seems solid and is not already crumbling/cracking.

**ravenscar** · 11-05-2010, 07:36 AM

thank you, i will try this when i can. any floridans have a nice steady supp. of coral from schools and biuldings.

**crashdive123** · 11-05-2010, 07:46 AM

The baked coral that I use was heated gradually to 500 degrees. Not sure what the starting point was, but Canids description sounds about right. Total process was about 10 hours.

**your_comforting_company** · 11-05-2010, 09:17 AM

I believe my mentor's suggestions are right on par with CanID, but I think he let his stay at 450 for 4 hours, and then he steps it back down the same way as going up.. in 50 degree increments per hour.
I also think he uses sand in his pan just in case any blow up.
Do NOT use your indoor oven, as when many of the "rocks" heat up and the molecular water is driven off, so is cyanide and several other poisonous gasses.

I have not had much success in cooking rocks or wood, myself.. they tend to blow up with me. I will be doing more experimenting with primitive methods of firing now that the weather is cooler.
I do know that calcium is NOT stable in extreme temps so caution should be use when cooking any limestone, or ocean rock. Some materials can explode rather violently.

**ravenscar** · 11-05-2010, 10:00 AM

your making me have second thoughts......

**your_comforting_company** · 11-05-2010, 10:08 AM

A little common sense, a lot of research, and always putting safety first. You'll be fine.
Just don't cook the rocks inside the house!

**ravenscar** · 11-05-2010, 10:10 AM

its a good thing you piped up, i was gunna pop them in in a few....

**oldtrap59** · 11-05-2010, 05:18 PM

I have two old videos. One on bow building and one on knapping. Haven't watched either for some time now but do remember that the guy that did the knapping video made the comment several times when talking about prep of the chert and heating it to be very careful. He used a metal 5 gal bucket and covered the chert with sand to heat his material. Not sure this is common practice but he seemed to think it needed to be done. Said that cracks and moisture in the chert could cause some real problems safty wise when raising the temp to high levels. This old boy said that the bucket and the sand did alot to hold down flying debris. If I remember right this guy stated he had been knapping for 30 plus years so maybe he knows something. Btw. Looking at his hands in the tape made it easy to believe that he had been at it that long.

Oldtrap

**canid** · 11-05-2010, 05:31 PM

the sand helps keep the heating even, and helps keep the cooling slow and even after.

it's not necessary, it's just one way to do it. another way to do it is to heat treat your rock in a deep fryer.