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Post by bobby1 on Jan 23, 2014 1:03:58 GMT -5
I tried heat treating some Brazilian Agate slabs with questionable results. Because the unheated slabs had a little red in them I thought I might be able to enhance the colors. Here is an example of the slabs before heating them. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated_zpsc2316d40.jpg) Here is what they turned out looking like. Instead of red I got brown. I suspect that I heated them too long and at a too high temperature. I held them at 600 deg. for 4 hours. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated1_zps59ac4601.jpg) Here is one backlit. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated3_zpsf61aabb4.jpg) This is one that did turn out to have a really nice (but again, brown) pattern. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated2_zpsdf18b77a.jpg) Here it is backlit. What do you all think? Bob ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated4_zps522ea680.jpg)
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Post by Rockoonz on Jan 23, 2014 1:15:01 GMT -5
Maybe jamesp can offer some enlightenment as to times and temperatures, I thought that some bake in red clay to get more of the red tones. Lee#2
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rockpowell
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Have been rock hunting most of my life, love cutting rocks, have tons of slabs, just haven't posted
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Post by rockpowell on Jan 23, 2014 8:27:02 GMT -5
I tried heat treating some Brazilian Agate slabs with questionable results. Because the unheated slabs had a little red in them I thought I might be able to enhance the colors. Here is an example of the slabs before heating them. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated_zpsc2316d40.jpg) Here is what they turned out looking like. Instead of red I got brown. I suspect that I heated them too long and at a too high temperature. I held them at 600 deg. for 4 hours. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated1_zps59ac4601.jpg) Here is one backlit. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated3_zpsf61aabb4.jpg) This is one that did turn out to have a really nice (but again, brown) pattern. ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated2_zpsdf18b77a.jpg) Here it is backlit. What do you all think? Bob ![](http://i151.photobucket.com/albums/s160/Rocksbob/New%20Photos/HeatTreated4_zps522ea680.jpg) ROCKPOWELL You did not mention what your process of heating was ? Oven ? We use crockpots with sand in them to heat agate slabs spaced a inch apart for 2 days at 500 dg. and let cool slowly for a day or so, thats so it take's all the moisture out, so we can chip arrowheads. Their is some color change, but not much. Would like to hear jamesp thought on this too, Also how long he cooked his coral at 170 in the oven, and if it was polished or just rough tumbled ?
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snuffy
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Post by snuffy on Jan 23, 2014 9:00:03 GMT -5
Very similar to the results I got cooking my Brazilian slabs.
snuffy
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jamesp
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Post by jamesp on Jan 23, 2014 9:17:01 GMT -5
The cooking process is perfect. And sand is fine. Masters in Indonesia use clays. Me not. If you got away with 600F for 4 hours and did not crack them then your heating and cooling cycle is very good. You got more color out of those slab than i would have ever imagined. Great job. The unheated slabs lacked color in the beginning. That is 99% of the issue here. The gray center changed more than i could do i think. Gray is void of many metal salts that make color. It is about the worst color to pull color. Brazilian is a pure and clean material. And the colors starting were 2-gray and brown. And brown usually turns darker brown. So you basically brought out the brown. And it paid off because Brazilian has such pretty patterns. Huge improvement. I gave up on mosses plumes jaspers from lava flows cause they are bad about turning dog do do brown no matter how i cook them. The colors to start with are yellow orange pink red light browns purples. Those are probably iron stained. And iron cooks good color. Or at least those colors intensify or jump to another color. Clear to white Yellow to orange Pink to beautiful(who knows w/pink) Red can go uglier to brown... Orange to red Light brown can be unpredictable. I get purple out of a certain orange/brown. But can not find that color in the field easily This flicker set is some early heats i did. Gives an idea of some colors of 6 batches. photo 1 is before, 2 is after 3 4 5 6 7 8 etc etc. So it is 6 batches to compare. The last 2 batches are from close to the ocean and have black. A mystery. Now collecting a wide range of color and expanded a lot. But the basic color changes are the same www.flickr.com/photos/67205364@N06/sets/72157632836510493
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Fossilman
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Post by Fossilman on Jan 23, 2014 11:08:31 GMT -5
I like them..........Those would make some great points....
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jollyrockhound
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Post by jollyrockhound on Jan 23, 2014 12:11:11 GMT -5
Nice esp the one with the banded
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Deleted
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Post by Deleted on Jan 23, 2014 13:11:12 GMT -5
I have read the entire thread. I might add that an attempt at 550 instead of 600 may be a good idea. That because your thermometer/thermostat isn't perfect and some are less perfect than others.
Still I loved to see the details you did bring out. Very nice for a first attempt.
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jamesp
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Post by jamesp on Jan 23, 2014 14:47:10 GMT -5
I have read the entire thread. I might add that an attempt at 550 instead of 600 may be a good idea. That because your thermometer/thermostat isn't perfect and some are less perfect than others. Still I loved to see the details you did bring out. Very nice for a first attempt. The end temp is really critical Scott. My first oven did 550. Second one did 600. With the coral i had substantial color increase. I have a big chunk of coastal chert that i broke to small pieces. They go from yellow to red at 600 and not at 550. I stick them in several spots on every cook to use them as 'litmus paper' to see where the cold spots are and as an indicator to turn oven off. If the rock will stay together at higher temps then i prefer higher. His slabs have no pocking or cracks and that intense deep color change is exceptional. I cook Montana and Brazil in small bits w/the coral and they behave very similar. I have been recooking stuff from the old oven to add color. And was frustrated that i was not hot enough for so many cooks. Other materials dance to their own drummer. But i know Brazilian pretty good.
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Deleted
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Post by Deleted on Jan 23, 2014 16:38:06 GMT -5
I only made the suggestion due to possible error in thermostat. It may be 600F at 550 readout/setpoint. Hell it could be 600 at 650 readout/setpoint.
You had to dial in your equipment to find the sweet spot. That is why I made the suggestion I did.
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Sabre52
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Post by Sabre52 on Jan 23, 2014 18:17:17 GMT -5
I had about the same results as you when I tried it. Also spilled sand all over the inside of my wife's stove and got in big trouble *S*. I have some very red treated material from Brazil via Quartzite and it was definitely soaked in mineral salts before heating.....Mel
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jamesp
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Post by jamesp on Jan 23, 2014 19:26:21 GMT -5
I only made the suggestion due to possible error in thermostat. It may be 600F at 550 readout/setpoint. Hell it could be 600 at 650 readout/setpoint. You had to dial in your equipment to find the sweet spot. That is why I made the suggestion I did. It is a big problem at high temp Scott. The thermometer is a huge problem. And the distance from the element. And the amount of rocks,the way they are stacked,etc. That is why i put those small pieces in the oven on every cook. If the top pieces do not get hot enough i recook them. If the thermometer is line of sight w/the heat source it throws everything into deception. Now i cook over 100 pounds at a time and am picky about the temp profile in the whole oven. It is the #1 problem w/cooking rock in my oven any way. The #1 oven is still her kitchen top oven. Because it is convection and the elements are behind a stainless deflector eliminating radiation. The heat is about 100% convection. It cooked very even as it does food. Another strange phenomena is slabs must be heated hotter. Big chunks get way hotter than slabs. Don't know why.
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Post by roy on Jan 23, 2014 23:11:51 GMT -5
the last one is nice !
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Post by pghram on Jan 24, 2014 11:29:45 GMT -5
Even though you didn't get the red you were hoping for it's still a big improvement.
Rich
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mjflinty
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Post by mjflinty on Jan 24, 2014 13:19:54 GMT -5
If you're not going to do anything with them, I'd be happy to trade you something. I'll knap them into spear points and knives :-)PM me
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Post by 1dave on Jan 24, 2014 16:03:24 GMT -5
Another strange phenomena is slabs must be heated hotter. Big chunks get way hotter than slabs. Don't know why. That is a poser! As water gets colder the molecules get smaller. After a while the top cold layer will flip over - Lake Turnover - and the heavy cold water sinks to the bottom, then the top water gets cold and when everything is about 32 oF it finally starts to freeze. Perhaps thin slabs radiate more efficiently?
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jamesp
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Post by jamesp on Jan 24, 2014 16:46:49 GMT -5
I can not say for sure Dave. I am thinking radiation is the issue. I can tell that Brazillian got hot because of the dark color. If Bobby cooked large pieces it may be too hot.
I have learned to heat big chunks and then slab. Firstly, the oil burns and discolors slabs badly. And cooking big chunks is cheaper cause the oven can stay on for a shorter period to get the same effect. Some oils stain worse. Used motor oil is bad when mixed with kerosene. Stains very badly. Clean motor oil mixed with kerosene hardly stains.
My friend has a hotter oven. He is a knapper and a 20 year rock cooker. I gave him some of my coral and what turned tangerine(sexy) orange in mine went to brown in his. His is really a kiln with circumferential heat element all the way around the hot box and 4 inch fire brick and $2000 computer control. No hot/cold spots. Scott made mention of thermometer inaccuracy and he is dead right. Once you get to 400F and higher you need good thermocouples and good heat distribution and controllers. My oven was made to heat highly conductive welding rods and only needs a bottom element. I am using it for insulative rock and i have to organize the load a bit. Chips and slabs in sand in pans in the bottom and the less demanding chunks in the cooler top section. But i finally whooped up on the situation.
I will say that our coral and coastal plain chert that was formed by precipitated water out of limestone and clay is so easy to get wild colors out of. Also agatized death plate.
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Post by 1dave on Jan 24, 2014 19:09:42 GMT -5
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jamesp
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Post by jamesp on Jan 24, 2014 19:43:12 GMT -5
Not tried any soaking yet. I will say that most coral is impermeable and will not take minerals of fluids. Even sitting in mineral rich conditions for many years. Only 1 out of 20 change well. I can usually tell by the initial color. My challenge is finding coral w/initial color. The next biggest problem i have is drying it out. It takes 3-4 dry out heat ups at 200F to get the moisture out of it. I keep them in the greenhouse to assist drying. The best cookers hold the rocks at 24-36 hours to get the moisture out. So i have been busy drying them to cook them. I did soak some in rusty rusty water with no effect. I know the conditions that cause mineral penetration. It is the only places i hunt coral for heating. I am not running out of colors yet. When i do i will want to do mineral salts,perhaps with strong vacuum chamber. And i have covered about 2% of coral territory. It may take a lifetime.
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