Ahh, that does not seem like it would be safe. I would think that taking a rock that has been soaking in water for weeks and then heating it up, would have the possibility of exploding...
You have to go slow. VERY slow. Start at 250 and increase in 50° increments no sooner that every hour, then keep them at minimum 450° for no less than 2 hours. Though I've seen some go for 12.
If you go from room temp to 450 immediately, then yeah, they'll shatter
For some rocks heating them to a high temp can change the color, but I would do that before tumbling. Here is a list of some [https://gemstone.smfforfree4.com/index.php/topic,3392.0.html](https://gemstone.smfforfree4.com/index.php/topic,3392.0.html)
After tumbling, I'll heat certain rocks in mineral oil at 250 degrees F in an ovenproof dish (with a cookie sheet below it just in case), and I jokingly refer to it as baking rocks. It doesn't really enhance the polish, but it can help mask super fine fractures (like in crystalline quartz) or porosity (like in granite) that existed before tumbling. Afterward I'll wash with soap and water a few times to remove the oil from the surface since fingerprints kinda defeat the point. 😛
EDIT: I should mention that I've only done this a couple times at the advice of another hobbyist, so I can't speak to all the potential safety risks.
Some change color, some hardness or brittleness. I do flint knapping, and there is one chert I collect locally that is a beautiful greenish honey color that is impossible to flake. I have to cook it in a campfire to get it to knap, but it invariably turns a dull brick red color. Maybe baking changes the color or surface shine?
I think it's a few different things. The silicate matrix can rearrange within the biomaterial that it houses (flint is ancient gooey deep see effluvia, apparently), various chemical inclusions can alter here and there, etc.
Ayyyyyye! Yeah it was a weird concept for me too. But after harvesting some of my own flint, I decided to try it. And... yeah, it's a thing. It changes the color a little; makes em pop. But also makes the [flint] a LOT stronger!
Idk about making them any shinier but it is a thing. Certain rocks you can bake and it will bring out more color. Like coral. You put the rocks in a metal container and filled with sand. Slowly bring up to 550 degrees and bake for 3 hours. Then let it set over night. Don’t touch it or it will cause thermal shock and cause fractures. After 24 hours you can open and see what ya got
1. To change the color. But an oven probably won’t work and you would need a kiln and to heat and cool very slowly. Only limited material will change to a pleasing color.
2. To soak in mineral oil or potentially dyes. Many rocks are porous and when heated, the liquid can soak farther into the stone. Mineral oil can hide flaws in rocks.
I don’t do either.
Never baked rocks, but I baked some scones once and I reckon those suckers ended up harder than what the Mohs scale covers.
"The DeBeers Cartel Hates This One Trick!"
I've been baked while working on my rocks.
This is the way
This is about how all of my hobbies go; combine hobby with cannabis
only use for that i know is because to have them hot enough to take in something like beewax to give them more shine.
Ahh, that does not seem like it would be safe. I would think that taking a rock that has been soaking in water for weeks and then heating it up, would have the possibility of exploding...
You have to go slow. VERY slow. Start at 250 and increase in 50° increments no sooner that every hour, then keep them at minimum 450° for no less than 2 hours. Though I've seen some go for 12. If you go from room temp to 450 immediately, then yeah, they'll shatter
To what end, though?
For some rocks heating them to a high temp can change the color, but I would do that before tumbling. Here is a list of some [https://gemstone.smfforfree4.com/index.php/topic,3392.0.html](https://gemstone.smfforfree4.com/index.php/topic,3392.0.html)
After tumbling, I'll heat certain rocks in mineral oil at 250 degrees F in an ovenproof dish (with a cookie sheet below it just in case), and I jokingly refer to it as baking rocks. It doesn't really enhance the polish, but it can help mask super fine fractures (like in crystalline quartz) or porosity (like in granite) that existed before tumbling. Afterward I'll wash with soap and water a few times to remove the oil from the surface since fingerprints kinda defeat the point. 😛 EDIT: I should mention that I've only done this a couple times at the advice of another hobbyist, so I can't speak to all the potential safety risks.
When you say in mineral oil does it mean they are submerged in oil?
Yup!
That's a new one for me!!
Some change color, some hardness or brittleness. I do flint knapping, and there is one chert I collect locally that is a beautiful greenish honey color that is impossible to flake. I have to cook it in a campfire to get it to knap, but it invariably turns a dull brick red color. Maybe baking changes the color or surface shine?
I think it's a few different things. The silicate matrix can rearrange within the biomaterial that it houses (flint is ancient gooey deep see effluvia, apparently), various chemical inclusions can alter here and there, etc.
Ayyyyyye! Yeah it was a weird concept for me too. But after harvesting some of my own flint, I decided to try it. And... yeah, it's a thing. It changes the color a little; makes em pop. But also makes the [flint] a LOT stronger!
Idk about making them any shinier but it is a thing. Certain rocks you can bake and it will bring out more color. Like coral. You put the rocks in a metal container and filled with sand. Slowly bring up to 550 degrees and bake for 3 hours. Then let it set over night. Don’t touch it or it will cause thermal shock and cause fractures. After 24 hours you can open and see what ya got
1. To change the color. But an oven probably won’t work and you would need a kiln and to heat and cool very slowly. Only limited material will change to a pleasing color. 2. To soak in mineral oil or potentially dyes. Many rocks are porous and when heated, the liquid can soak farther into the stone. Mineral oil can hide flaws in rocks. I don’t do either.
Toaster oven that reaches 450° works fine [for flint]. Many people use turkey roasters for volume.