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Post by deb193redux on Oct 24, 2009 15:54:38 GMT -5
Since EarthDog posted about the GemShop's Tuxedo agate a few years ago, I have had it in mind to try and make some. I got a few slabs from theGemShop at the World of Agate show, and I think their stuff was better. But maybe that was after they threw out all the rejects. Also, they had smoother saw cuts than I made with the WF, so mine looks more frosted when it is dry. When I unpack the box with those slabs, I will post pics of their stuff. Anyway, I read up and understood the general recipe was to soak in sugar water for a few weeks and then simmer in sulfuric acid for a few hours. The GemShop used Moroccan Agate that had white bands on light gray/clear agate. I tried half Moroccan and half very light colored Madagascar agate. I need to find my pics of the untreated stone. Will add them later. First attempt to was a bit disappointing. Got it cooked just before I moved in August. Mostly brownish instead of black tones (click for larger) Here it is dry: ... and wet: This last one shows the Madagascar, which had more lacy pattern Now that I am settling in and unpacking, I thought I would try to re-cook them. I suspect it was not hot enough the 1st time. Or, possibly since the slabs were not completely dry, the water in the rock kept the acid from penetrating as well. Got much darker results. A few pieces just did not take treatment. The end cuts tended to be denser and did not take the sugar. Here is the re-cook shown dry: This last one shows a Prudent Man Agate endcut I threw in just to see: Here it is shown wet: Some of the white parts lost a little luster. I need to grind a bit and see if thats just on the surface. Might be a delicate balance of getting enough sugar into the clear parts w/o getting any into the harder white parts. I also think the Madagascar looked better in espresso. Not sure how much I will fuss with this trying to perfect the effects. I tend to move on to other projects. I have most of what I found on this topic in either books or web pages scanned into a PDF file. It is about 3.5M. If you want a copy PM me. I will hang it one the web at some point.
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lapidopterix
starting to spend too much on rocks
Member since March 2008
Posts: 216
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Post by lapidopterix on Oct 24, 2009 16:55:05 GMT -5
That last batch looks really good. Does the color go all the way through?
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Post by deb193redux on Oct 24, 2009 17:03:54 GMT -5
on most pieces the color does. on others i can see the color stop along density zones - not depth. all the literature says the carbon deposits throughout, but there has to be a thickness limit after I cut and grind, i could always sugar and cook the preform. Here are some wet scans. On some the color tails out. Has to be density contours (click for larger) Maybe some virtual cabs too: had to virtual cab the prudent man
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Post by frane on Oct 24, 2009 19:58:38 GMT -5
Well, I sure think they look pretty! Neat experiment! Fran
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Post by Toad on Oct 24, 2009 22:18:33 GMT -5
Let me get this straight - you heated acid???
Nice looking slabs.
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Post by deb193redux on Oct 24, 2009 22:43:55 GMT -5
Yes - with care, and a simmer instead of boiling. The boiling point is 554, and that is very hot.
The Romans used acetic acid and it boils closer to water. The Germans perfected the modern recipe and they used sulfuric.
I had use of a fume hood in Oregon, but in Kansas I am using the patio. At some point I will need to see if boiling really does make a difference, but I think I will work this stuff first.
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adrian65
Cave Dweller
Arch to golden memories and to great friends.
Member since February 2007
Posts: 10,772
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Post by adrian65 on Oct 25, 2009 0:44:00 GMT -5
I enjoyed the slabs you showed me when we met in Cameron, but the last ones show a bigger contrast, indeed. Your virtoal cabs show a great potential of those slabs.
Is that treatment stable in time?
Adrian
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Post by Toad on Oct 25, 2009 0:57:50 GMT -5
Yes - with care, and a simmer instead of boiling. The boiling point is 554, and that is very hot. The Romans used acetic acid and it boils closer to water. The Germans perfected the modern recipe and they used sulfuric. I had use of a fume hood in Oregon, but in Kansas I am using the patio. At some point I will need to see if boiling really does make a difference, but I think I will work this stuff first. Acetic acid isn't much stronger than vinegar, is it?
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,455
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Post by Sabre52 on Oct 25, 2009 7:16:21 GMT -5
Man, I'm impressed! Excellent experiment! Those came out real nice and it's sure a big improvement on plain old gray and white banded material. I like the black and white way better than all those bright colors some folks color the Brazilian material.....Mel
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Post by deb193redux on Oct 25, 2009 10:11:55 GMT -5
Mel, I agree that black, or natural tones, is the only dying that interests me. I also like the history of this. Like knappers often report feeling connected to ancestors who knapped, I like thinking I am studying something that early stone workers discovered. (But, can't anyone who bakes bread say this? LOL.)
I am trying the more patterned stones because I want it to be very recognizable as agate. Some of the Moroccan, with only a few bold white lines, could be mistaken for glass.
Todd, acetic acid would be safer, but does not go much past brown. Still, I might consider an experiment where I spend a season in Corsica and work with honey and vinegar. That could be fun.
Adrian, the sugar molecule is hydrogen oxygen & carbon. The acid makes hydrogen sulfide gas and oxygen. It leaves pure carbon, which color is stable with time.
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Post by deb193redux on Oct 25, 2009 10:23:39 GMT -5
This is from Kurt Nassau's book, which was a large part of the research material I assembled befor I began. It looks better in PDF.
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altamura
starting to shine!
Member since September 2006
Posts: 34
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Post by altamura on Oct 29, 2009 20:48:02 GMT -5
Spectacular work Daniel! Your methods and tie in to the historical efforts to dye agate is fascinating. Keep us informed.
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Post by Woodyrock on Oct 30, 2009 1:38:55 GMT -5
Toad: White vinegar is a 5% solution of water, and acetic acid. Woody
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Post by Tonyterner on Oct 30, 2009 13:07:06 GMT -5
Very cool with some great looking results. I love to see people experiment.
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mossyrockhound
fully equipped rock polisher
Member since January 2011
Posts: 1,278
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Post by mossyrockhound on Oct 31, 2009 18:39:34 GMT -5
Cool thread! Thanks for posting. I learn something new nearly every time I check out this forum. Garry
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Post by helens on Feb 27, 2012 17:57:22 GMT -5
Bumping this thread too, I'd love a copy of the pdf Daniel!! But I'm more interested in your process. I've seen people talk about it, but when the 'sulfuric acid' discussion gets started, I think... uh... no. I'm not going to order sulfuric acid:P. But it can be done with vinegar??
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Post by deb193redux on Feb 27, 2012 18:09:31 GMT -5
Most time you hear of cooking, it is just heat to deepen reds or change texture for knapping. The Romans did it with vinegar, concentrated I think. 17th century Germans added the sulfuric acid twist. I will locate the PDF and attach it to a PM. Meanwhile, you can google: Fisher agate induce black ... and it is the 1st hit. www.ganoksin.com/borisat/nenam/black-dying-agate.htmmost of what I have in the PDF is there. You can possibly skip the acid and get dark brown results with several hours in a 400 degree oven. The instructions for boiling the acid are a bit scattered. Fisher just mentions "boiling", but there seem to be two boils. One where the water comes out and the solution concentrates, and then the listed boiling point of sulfuric acid, which is about 600F. I don't think Fisher meant the latter, but he is not around to ask. Finding a hotplate that goes to 600 can cost over a hundred even for used on ebay. Not your standard home model. I have tried a Coleman stove, which worked OK when the container was full and the rock could not move to much, but once when there was just a few slabs and one was big, it knocked against the side of the Pyrex until it chipped it and the acid pored out on the stove and ate away the paint and then it rusted. (Also I had a moment of fear as I wondered if the acid was flammable - fortunately NOT.) Using a Safflower oil bath in a roaster that went up to 475F, and putting my Pyrex beaker down in that seemed to be the safest way. But I left the roster outside to cool so I could drain the oil, and it rained and washed the oil all over my patio. I got discouraged and just left it sit outside all winter. Next spring the roaster did not work anymore. Go figure. My next batch is small and I think I will go back to the hotplate since I will only to heat about 1.5 cup of acid.
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Post by helens on Feb 27, 2012 19:19:01 GMT -5
Hi Daniel:).
So if you can heat it, you don't have to use any acid, but it will only get to brown, not darker?
Most ovens clean at 550 degrees right? Why can't you put the pyrex bowl with the rocks inside the oven instead of doing it stovetop? It would not go to 600 degrees, but it's pretty close.
I'm a glass artist so I have a kiln, I can heat up to 2300 degrees F np, raising it 1 degree a minute if necessary. So heating wouldn't be a problem. I just don't want the acid laying around. Also, is there a heating speed?
What a scary thing to happen to you with the spill! That's almost the worst nightmare. Cleaning up the acid must have been terrible... heating acid produces fumes too right? I know hot lye can fume, and if you stand there whiffing it, it can potentially melt your lungs.
A safflower oil bath is expensive!! Safflower oil smoke point is 510 degrees. But pure Soybean smoke point is 495 degrees, so for 475, soybean (not a blend) will work. Since you aren't needing to actually hit 500 degrees, soybean may save you a little money (Corn oil is 450 degrees). Could you contact a glassmaker or ceramics maker in your area? They would have kilns... and could put the acid bath right into it without worrying about a bath. Other option is to buy a cheap used kiln. It's still going to cost over $100, but if you do a volume of rocks, that would recoup it without the dangers you're putting yourself in, or having to buy perishables every few batches.
What would be a reasonable experiment for just heat, without the acid? Just put rocks in kiln and heat to 400 degrees to see if colors change?? How do you decide which rocks might benefit from this?
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dbrealityrocks
fully equipped rock polisher
Member since February 2010
Posts: 1,084
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Post by dbrealityrocks on Feb 27, 2012 19:48:34 GMT -5
very cool... isn't this also about the way they treat Andamooka opal?
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Post by deb193redux on Feb 27, 2012 20:03:33 GMT -5
I just read up on it and it seems that they color/carbonize the matrix stone to better show the opal with a sugar acid treatment. I found this: www.shed.com/aom/storyfile/ammatrix.htmlwhere a guy use battery acid (says it is less potent than pure) and only uses temperatures upto about 160. Interestingly, he also uses heated sugar solution too.
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