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PostPosted: Wed Aug 06, 2008 10:35 am 
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Hi,

Nice conversation guys.
Roger may I use your 3 images for the Gemology Project?

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 Post subject: re: red/pink Tourmaline heat treatment
PostPosted: Wed Aug 06, 2008 10:54 am 
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Doos wrote:
Hi,

Nice conversation guys.
Roger may I use your 3 images for the Gemology Project?


Yes, of course. I suppose you would prefer to have JPEG's without any text layed over the photo? If so, I can re-send or handle it however you prefer.

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PostPosted: Thu Aug 07, 2008 11:20 am 
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Great results, Roger. Inspired by Lisa's instructions and your image I decided to have another go at it. I used my programmable oven following Lisa's instructions, ramping in increments of about 250 F. to a heat-soak temperature of about 960 F. with a 2-hour hold.

In the images below, made with diffused daylight, the top one shows "before heating" colors. Note that the two cut stones had previously been heated with the method described earlier in this thread. I re-heated them hoping for some miraculous kind of alchemy. No cigar.

The stone on the left lightened in color but still retains some very slight pinkish-brown hue. The one on the right changed from slightly pink-brown to nearly gray. Both were originally dark purplish red with a slight brown overcast.

The two roughs were being heated for the first time. The one at center left lightened in tone but retained its original orangy-red hue. The stone at center right originally was darker in tone than is shown in the 'before' image, and it lightened to a lovely vivid pink.

I think the old garbage in, garbage out principle applies here. I believe heat will emphasize brown and drive off reddish hues in certain Nigerian stones. They are not all chemically identical, as jleb outlined earlier, and respond differently to heating.

Before heat:

Image

After heat:

Image

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PostPosted: Thu Aug 07, 2008 8:44 pm 
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Hey Rick,
You really "got lucky" there, rough usually pops. In the future grind the skin off and get it clean or you may be sorry.

When we didn't know better we heated 1 KILO of this pink material in the rough, we had MAJOR breakage, lost a lot of money.

Have fun with your experiments!

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PostPosted: Thu Aug 07, 2008 9:20 pm 
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Thanks for the info John but I know the risks. I was willing to chance breakage for a quick test.

Why don't you chime in with some of your heating methods? I'm sure we'd all like to learn more from someone who has a lot of experience.

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PostPosted: Fri Aug 08, 2008 11:16 am 
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Hi,

I've update the gem project. Thanks Roger and Lisa .. and everyone else of course.

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PostPosted: Fri Aug 08, 2008 12:29 pm 
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I just heated 2 Nigerian stones that I had cut, that were on the dark side. Used the same procedure as Roger, and both came out a very nice pink color. I have tried some of the more brown material in the past, and didn't have much luck with it.

I know that that darker red tourmaline up on the Precious African Gems site does heat well to a bright pink color.

Has anyone tried any of the darker green congo material? I was told that it will lighten and get a more neon type color. Of course this was from a guy selling it.

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 Post subject: heating tourmaline
PostPosted: Fri Aug 08, 2008 12:36 pm 
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I'm glad my recipe is working for people! I cut lots of the darker reds - when you buy it by the kilo that happens - but the stuff varies from mine to mine. Anytime I get a new parcel I run another set of tests on some of the nastier chunks.

My experience lightening greens hasn't been as consistent as the Nigerian rubellites, though.

Lisa

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PostPosted: Fri Aug 08, 2008 1:09 pm 
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Rick, are those photos representative of the actual color resulting from the treatment? I only ask because I see a decidedly "pink" cast to the background in the second image that's not in the first and I wonder if the color balance is the same...


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PostPosted: Fri Aug 08, 2008 2:24 pm 
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The two images were shot with the same white balance using natural daylight but at different times of day. The top exposure was made in the afternoon, the lower one fairly early in the morning when there's more red in the light.

Neither image is an exact reproduction of the actual hues/tones, as is often the case with digital images. No photoshopping was done other than to increase brightness slightly. IMO the colors are pretty close to real life. I'm always more concerned with the color of the object being imaged than backgrounds.

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PostPosted: Fri Aug 08, 2008 2:31 pm 
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ROM wrote:
IMO the colors are pretty close to real life. I'm always more concerned with the color of the object being imaged than backgrounds.


Good to know. I assumed that was your primary concern, but figured it best to ask. :) I'll have to go look over my tourmalines and see if there's any that are currently "junk" that it might be fun to subject to a heat experiment. :)


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 Post subject: heating tourmaline
PostPosted: Fri Aug 08, 2008 2:52 pm 
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If you're really going to experiment, saw a single piece into 2-4 smaller ones and keep a control, as well as several test subjects. This works best when you have a parcel of similar material :-) (no point killing the only rough you've got) and the testing process is absolute hell on the electric bill.

Cheers,

Lisa

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PostPosted: Fri Aug 08, 2008 6:21 pm 
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My two cents worth:

If it ain't clean it is really risky!

Over 400C take it up only 10 degrees a per try as color start changing FAST.

Some of the ugly body tones are due to a green or blue component, this will NOT come out but if you heat out the pink you might have an interesting light green/blue or grey gem. This is a bit like Russian roulette so if it is pretty at some other stage probably leave it as is. The risk is that often the underlying color isn't that pretty either. But sometimes it is.

I usually "soak" for an hour but in my mind it is more to get the temperature to normalize all through the crucible, I haven't noticed much difference with longer "soaks" but haven't tested it that much to be sure.

I suspect a lot of the improvement on green from some locales comes from removing a bit of pink, just a guess though.

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PostPosted: Fri Aug 08, 2008 6:23 pm 
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johnddyer wrote:
My two cents worth:

If it ain't clean it is really risky!

BUY A COMPUTERIZED CONTROL


My electric bill was not nearly as high as I suspected with my computer controlled oven running. Maybe the fact that it cycles the element on and off for short periods has something to do with it.

Over 400C take it up only 10 degrees a per try as color start changing FAST.

Some of the ugly body tones are due to a green or blue component, this will NOT come out but if you heat out the pink you might have an interesting light green/blue or grey gem. This is a bit like Russian roulette so if it is pretty at some other stage probably leave it as is. The risk is that often the underlying color isn't that pretty either. But sometimes it is.

I usually "soak" for an hour but in my mind it is more to get the temperature to normalize all through the crucible, I haven't noticed much difference with longer "soaks" but haven't tested it that much to be sure.

I suspect a lot of the improvement on green from some locales comes from removing a bit of pink, just a guess though.

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Artisitic and designer cut gems

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 Post subject: re: red/pink Tourmaline heat treatment
PostPosted: Sun Apr 12, 2009 11:02 am 
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Hey guys.....
Thought I would give the heat treatment another test run. Worked on four Nigerian Tourmalines, all fairly dark. The photo below shows the outcome. The photo also contains a 'control' stone - on the far right. They started out all about the same color.
Image
Needless to say I was a little disappointed.... back to the drawing board.

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