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sugar - acid Tuxedo agate

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Author Topic: sugar - acid Tuxedo agate  (Read 2367 times)
deb193
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« on: July 26, 2010, 05:32:59 pm »

I have been trying to develop a good procedure for making sardonyx using the ancient sugar-acid methods. Mostly I'm relying on George Fisher's writeup in his book, and a similar account by Kurt Nassau. I have had some good to mixed results, but it is a work in progress.

I was inspired when I heard theGemShop had made a batch in 2005 which they marketed as Tuxedo Agate (http://thegemshop.com/osc/gal_cab_tux_05.php)

I bought a few slabs from them in 2007 at the World of Agate show (see below). On a recent visit to the shop, they only had one bag left. It had about 8-10 slabs and was priced at $150. I paid $29 for my 3 slabs. They are cut thin because there is a limit to how deep the treatment penetrates. I am working to understand how to get the deepest penetration. The thickest one is 5mm, but the thinest is only 2.8mm.




Here is some of what I cooked:








Some preforms:


I made some thick slabs and cut some high domes. I lost the color on the edges, so I soaked them in sugar again, and cooked them again. Here is some of the ones done twice shown at different stages. Currently this is 220g, and I need to sand and polish. From the top, dry, then wet, recooked on bottom)
« Last Edit: July 26, 2010, 09:57:51 pm by Taogem » Report Spam   Logged

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« Reply #1 on: July 26, 2010, 05:44:55 pm »

WOW!  What a difference between the original material and your cooked versions.  It really brought out the banding!
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« Reply #2 on: July 26, 2010, 05:58:09 pm »

What striking results you got.  How long at each temp, and what's the sugar acid part, if I may ask?
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deb193
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« Reply #3 on: July 26, 2010, 06:14:42 pm »

Prolonged soaking in a saturated sugar solution gets sugar molecules into the pore space of the agate. About 3 weeks at room temp. Some agates have more pore space than others. Moroccan and Brazilian work well. Sugar is a compound of Carbon Hydrogen and Oxygen. The acid strips off the hydrogen and oxygen (making water and other vapors). In ancient time it was acetic acid (vinegar). Today sulfuric acid is recommended, but it is more hazardous to handle. Simmer at about 350 F to 390 F for one to several hours. (Some recommend longer and/or hotter). Neutralize with water and soda after removing rock from acid.

More details are online in George Fisher's book. But things like exact concentration of acid and exact temperatures are a bit fuzzy.

Soaking in sugar at 120 F was a bust because it formed a syrup that did not seem able to penetrate as well as thinner mix at room temp.

I am going to try fructose instead of sucrose, because that is a smaller molecule. I am also experimenting with heat instead of acid to carbonize the sugar, and trying other types of agate. I tried to actually boil the acid, but as I passed 475F there was way too much caustic smoke - even for outdoor cooking. I may try a 24hr simmer at just under 300F.
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« Reply #4 on: July 26, 2010, 06:16:13 pm »

These agates are more beautiful up close. MOst of them are a delightful chocolate brown color:)
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« Reply #5 on: July 26, 2010, 09:52:48 pm »

Daniel, thanks for that info.  So, first you soak it in a sugar soln. , then simmer in vinegar? , and then neutralize and that beautiful stone results.......if you're lucky.  Is that the order?
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deb193
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« Reply #6 on: July 26, 2010, 10:00:19 pm »

well, the Corsicans and Romans used vinegar. I use concentrated sulfuric acid obtained from bio-diesel supplier. I understand vinegar does not get as black.
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« Reply #7 on: July 26, 2010, 10:05:30 pm »

A few recommendations form an old chemist.

1.) heat the agate to about 100C and hold it for a while to de-gas as much as possible and dehydrate making the pores open up as much as possible. A light vacuum will help here too.
2.) try pulling a vacuum on the agate and the sugar solution while in the soaking process. If there is any gas in the pores the vacuum will help remove it, and allow the liquid to penetrate.
3.) one of the most porous agates around is snake-skin agate, it's the one they used to use to make the  copper dendrites form by induction with an iron nail.

I would guess you can get a simple vacuum from a 5 gallon plastic pail with snap on top (Like the ones used in 5 gal paint cans), put a pipe fitting on top with a simple on/off valve. Use a shop-vac to pull the vacuum when filled. and then close the valve.

Anyway just some old tricks for degassing porous catalyst before we used them in some liquid chemical reactions. It improved the liquid contact in the porous structure of the catalyst.

ron
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« Reply #8 on: July 26, 2010, 10:09:39 pm »



More details are online in George Fisher's book. But things like exact concentration of acid and exact temperatures are a bit fuzzy.

Soaking in sugar at 120 F was a bust because it formed a syrup that did not seem able to penetrate as well as thinner mix at room temp.

I am going to try fructose instead of sucrose, because that is a smaller molecule. I am also experimenting with heat instead of acid to carbonize the sugar, and trying other types of agate. I tried to actually boil the acid, but as I passed 475F there was way too much caustic smoke - even for outdoor cooking. I may try a 24hr simmer at just under 300F.

This is really interesting Daniel.

When it comes to chemistry, I do not have any input or answers except to imagine it is like mixing any other chemicals for any number of applications. There is a pretty specific mix of each chemical, heat, and length cooking/mixing time that create the ideal chemical reactions for a perfect recipe.

These look really great. 5mm is certainly workable !

Black and white is beautiful !

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deb193
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« Reply #9 on: July 26, 2010, 10:13:10 pm »

the heating before soaking sounds useful, as well as the vacuum. Thanks. I was thinking about one of these canisters that you can pump out the air to keep coffee fresh longer. It is not high vacuum, but it might be enough.

The snakeskin is porous, and I have some to grow dendrites. But, no white bands. It would make an all black stone.
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MrsWTownsend
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« Reply #10 on: July 26, 2010, 10:41:29 pm »

I had no idea there was even such a process...  The results are spectacular!  I need to get me that book.  Thanks for posting this~ I am learning new things on this forum ALL OF THE TIME!!!!
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« Reply #11 on: July 27, 2010, 04:59:04 pm »

It's wonderful how much we all learn from this forum.
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« Reply #12 on: July 27, 2010, 07:47:16 pm »

Much of the Black Onyx slabs that you can buy (expensively!!) form various vendors has a strong chemical odor as you work it. I think they are treated in Germany with analine dyes.
Bob
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« Reply #13 on: July 27, 2010, 08:15:56 pm »

So, I have a stupid question....Why don't you do the grinding & forming BEFORE you cook the stone?

I get that it is nice to see the prefered finish color combos before you start....but if you waited - you would only have to do it once.

Connie
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deb193
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« Reply #14 on: July 27, 2010, 08:54:57 pm »

it is entirely my lack of imagination to "see" when looking at the plain stone. But, since I expect to have ongoing batches, throwing them back in is not a problem.
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