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Post by roy on Apr 18, 2012 9:28:35 GMT -5
this past weekend i seen some pokadot agate that had been heat treated but the one that did it has become ill and can no longer explain how it was done ! i was wondering if anyone know's how this is done or are there any books that i could obtain :help:
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Post by geoff on Apr 18, 2012 10:49:49 GMT -5
There is a great book about gemstone treatments. Its ridiculously expensive, so I borrow it from the public library every now and again. Pretty sure its called gemstones and their treatments, ill check at lunch.
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,690
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Post by Fossilman on Apr 18, 2012 11:56:46 GMT -5
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kevin24018
spending too much on rocks
Member since February 2012
Posts: 284
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Post by kevin24018 on Apr 18, 2012 14:31:58 GMT -5
check out some knapping sites, they heat treat to make the stone fracture better, now if you are talking about color change, like they do to sapphires, that requires expensive equipment (kiln) etc.
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Post by helens on Apr 18, 2012 20:36:57 GMT -5
Gaah... someone posted a few links to me a month or so back about how to treat Tuxedo agates... and I can't remember where now.... Aha! I found it! Daniel wrote it! It's how to dye agate tho, not heat treating: forum.rocktumblinghobby.com/index.cgi?board=sawingb&action=display&thread=33886Here is another thread about same topic: forum.rocktumblinghobby.com/index.cgi?action=display&board=sawingb&thread=38185&page=1If you need HEAT treating... ie., what Fossilman and Kevin said about flint... under the Creations section, one of the flint knife guys explained the entire heating process without a kiln when I asked him about it. Here is a good info link about temps, but they are talking about knapping flints: www.dances-with-snakes.com/recipes.htmI don't have any info about polka dot agates, but I have info on smoke treatment (opals), sugar treatment (opals), cooking tux agates, and matrix opal treatments (all of which can probably be cross adapted for different things. What exactly do you want them to do Roy?
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Post by roy on Apr 18, 2012 22:04:26 GMT -5
you know just something to do and we have kiln at work @ 800 it turned a little shade of red
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Post by helens on Apr 19, 2012 1:54:59 GMT -5
Roy, this is the Kiln part from that last link above: "Kiln Cooking
Kiln cooking rock is the most predictable method, especially if you have a computerized control device as you have the most control. Ramp times vary depending on material. A general rule of thumb is to dry your rock out at 200° for 8 hours, then ramp-up in 50° increments (spalls and smaller stone) until you reach the desired temperature, then hold for the desired "soak" time. For larger stone reduce this ramp-up and down times as larger stone does not absorb the heat as quickly as smaller sizes. Additionally, there are several varieties of stone that should also be ramped-up a bit slower: Harper, TX tabs, Rootbeer, Knife River , and Mozarkite(20-30° per hour). Frisco, Perdinales amoebas and some of the darker rocks should only be approached at 5° per hour. And it appears that ramp-down times are just as crucial as ramp-up times. In most cases 30° per hour is a good measure. A full kiln will ramp down slower than a half empty kiln. Also, one should test their rock to see if it cooks better in whole or slabs. Frisco , Montana agate, and Perdinales amoebas can only be cooked as THIN spalls or as slabs up to about 5/16 inch, while Burlington , Flint Ridge, Mozarkite, Knife River, and Kay County can easily be cooked whole. Care should be taken to assure yourself that there are not any enhydros (water pockets) in your rock as disastrous results can be obtained. Some recommend ramping all rock up 5 degrees per hour and down 30 degrees per hour, except for Burlington , Flint Ridge, and Kay County ."
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Post by helens on Apr 19, 2012 1:55:54 GMT -5
I'm going to assume you know what they mean by ramp up and other kiln terms... if not, just ask:). Does your kiln have a digital controller or is it manual with a pyrometer?
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Post by Woodyrock on Apr 19, 2012 1:57:21 GMT -5
Roy:
Check out the Puget Sound Knappers web site. We have a good tutorial on how to heat treat rock for knapping. Early knappers had this down to an art, since most agate, and jasper needs heat treating to be knappable. BTW, at the Polka Dot claim you can still see where the early Native Americans heat treated the Polka Dot agate. Since they did not have thermometers to control heat there is still a good sized heap of failures. They stand out from the raw material by the red colour. Woody
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Post by roy on Apr 19, 2012 9:21:18 GMT -5
thanks woody i will have to check that out the next time i'am up there! helen it is computer control and i do know what ramp up means thanks for your help!!
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Post by deb193redux on Apr 19, 2012 16:26:47 GMT -5
the tuxedo agate is really dying, and the heat is just incidental
a lot of agate and jasper fractures at temps much higher than 500F
Roy, what did the heat treated polka dot look lke? What had the treatment done?
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Post by roy on Apr 19, 2012 19:57:13 GMT -5
the piece i seen turn the white a deap red ! the one i did turned very faintley
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