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 Post subject: 14 steps traditional sapphire heating process
PostPosted: Tue Oct 10, 2006 8:43 pm 
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Hi Guys,

This is the first time we post our traditional sapphire heating process with detailed pictures. Our process is slightly different with the widely used and if you are interested, please send me private messages and I will share with you our long time kept heating secret. Our heating process is quick(about 2 hours), very effective in lightening up sapphires and turn pastel color into top cornflower blue color.

Step 1: Get the crucibles and aluminum oxide powder ready. Clean the sapphires and here we go.
Step 2: First of all, pour some aluminum oxide powders onto the bottom of the crucibles and then dump your sapphires on top of the powders.
Step 3: Now put more aluminum oxide powder on top of the sapphires. The aluminum oxide powder will help the sapphires be heated at more of less the same temperature and protect the sapphires.
Step 4: Then put the lids on the crucibles and sealed with a type of adhesive.
Step 5: Now the crucibles were sealed tight. Check again on the lids to make sure they are sealed tight. If the lids fall off during the heating, the sapphires can be dumped into the charcoal and you get nothing besides charcoal ashes finally.

Step 6: When the charcoals are piled almost to the top of the oven, put the crucibles inside.

Step 7: Put more charcoals around the crucibles and set them tightly in the middle of the charcoals. Make sure the crucibles fit tight.
Step 8: In about half an hour's time, the fan demonstrates its power - the top charcoals are burning with flames.

Step 9: Now it's about 1.5 hours and the oven reached the maximum temperature to 1700 C - 1800 C. The flames are more yellowish than red.

Step 10: Now it's almost 2 hours and the charcoal is burnt out and dropped to the bottom of the oven. Get a steel barrel by the oven and be ready for the next step of getting the crucibles out.
Step 11: After about 2 hours burning, now the crucibles dropped to the bottom of the oven. Use a long pincer to clip the crucibles out of the oven. It's big challenge for the operator as the temperature is burning high. Any mistake will cause the total loss of the sapphires inside. My uncle is an experienced heater and he never fails.

Step 12: The crucibles were quickly put into the steel barrel after being fished out of the oven.
Step 13: Now the crucibles were cracked open by a hammer. The inside temperature is still high. It's very important that when the sapphires were exposed, there must be no flowing air in the room. Otherwise it will leads to cracks in the sapphires during the cooling down process.

Step 14: The sapphires were exposed after the crucible was cracked. In about 10 minutes the sapphires will be cooled down to room temperature and ready for being cleaned and then cut.

Alex
www.china-sapphire.com
http://pg.photos.yahoo.com/ph/gembestbuy/my_photos


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 Post subject: nice!
PostPosted: Tue Oct 10, 2006 11:40 pm 
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can we see a close up of the finished product?? This is really great..


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PostPosted: Wed Oct 11, 2006 12:14 am 
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Hi,

I post a few pictures on a 40cts rough and a pastel color rough before and after heating. The most amazing thing is about the pastel color sapphire. Before heating, it was such a cloudy, milky slightly blue with greenish yellow cross table stone. After heating it turned into a top royal blue stone.

Most of the pastel colors can turn into nice blue color with good clarity after heating in our way.

Look at the comparison pictures at my album at: http://pg.photos.yahoo.com/ph/gembestbuy/my_photos

Alex
www.china-sapphire.com


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PostPosted: Wed Oct 11, 2006 12:34 am 
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Superb.
Thank you for taking the time to post this incredible tutorial.


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PostPosted: Wed Oct 11, 2006 1:26 am 
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I had no idea you could get that much improvement on heat treatment.. really great shots alex!


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PostPosted: Wed Oct 11, 2006 7:35 am 
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Yes, indeed a great post Alex!

Is this the standard procedure, or is it more common to have own adaptions like yourself?

Also, why is it that you've mixed both cut and rough stones? Is different colours better suited to burn cut resp. rough?

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PostPosted: Wed Oct 11, 2006 8:48 am 
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Hi,

Yes this is more or less the standard procedure in heating sapphires in a charcoal oven. There can be slightly different controls on temperature, time duration, cooling down time and other details which will lead to different heating results.

Usually we only heat rough sapphires and then cut and polish them. The few pieces faceted sapphires in the crucibles are from Montana and a few local pastel color sapphires.

The Montana sapphires are much cleaner and even lighter. Our local pastel colors changed into top royal blue. This standard heating process is very effective on basaltic sapphires like ours and those from Australia. But for Montana and Ceylon and African sapphires, we think there should be a different process, maybe lower temperature and longer time.

I wonder if anybody who knows that can share with us.

Alex
www.china-sapphire.com


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PostPosted: Wed Oct 11, 2006 9:43 am 
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Well done Alex! Thanks so much for sharing!

peter

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PostPosted: Wed Oct 11, 2006 11:04 am 
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Fantastic overview, Alex... I'm always impressed by the knowledge that our members share here in the forum.

Thanks for sharing with us!


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PostPosted: Wed Oct 11, 2006 10:43 pm 
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Great Alex!
It looks to me that you are using the same type of process as the Pailin burner I visited many times with the AIGS students on week end fieldtrips.
As you can see on the photos I put on the following page, it is very similar process. Great to share that with everybody...
http://www.fieldgemology.com/showpic.php?sub_id=58&type=school

All the best,

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The views expressed here are V. Pardieu’s opinions and do not necessarily reflect those of GIA Laboratory Bangkok (http://www.giathai.net)where he is an employee since Dec 2008.


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PostPosted: Thu Oct 12, 2006 2:11 am 
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Thanks Vincent. I just looked at the pailin heating pictures and realized we have more or less the same heat treatment process.

It's good to exchange thoughts, ideas and practical knowledge from each other on this forum and I learned a lot.

Alex


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PostPosted: Thu Oct 12, 2006 10:37 pm 
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Hi Alex,

Yes it seems that it is rather close. This treatment technique was developped by a Thai man: Khun Sammuang Kaewen in 1969 in Chanthaburi and performed on australian milky and silky sapphires. Later it will be used on Pailin sapphires and at the end of the 1970 it will become famous when applied to the Geuda type sapphires from Sri Lanka.
This technique without major changes is still used by some people around Chanthaburi but most of the Thai burners have now developped other techniques more efficient with better control of the heat treatment process.

Now to my knowledge most burners use some large capacity fuel furnaces to heat blue sapphires and if necessary as if the stone become too dark then they may use the new beryllium technique in order to lower the blue to more appealing levels. I imagine that using your technique many stones are turning too blue, are they?

All the best,

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The views expressed here are V. Pardieu’s opinions and do not necessarily reflect those of GIA Laboratory Bangkok (http://www.giathai.net)where he is an employee since Dec 2008.


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PostPosted: Fri Oct 13, 2006 3:42 am 
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Hi Vincent,

We tried with fuel oven and electric oven but none is better than the traditional charcoal oven. I suppose it's because of the procedure control. The electric oven has better control but the results haven't been satisfactory so far.

The heating process works best on sapphires with blue-grey cross table and the tone are lightened up substatially to expose more luster in the cut stones. For the over dark midnight blue, it doesn't change much. And for the milky sapphires(we call them natural blue locally), the stones are getting too blue like you said. Usually we will heat them for the second time to reduce the saturation a little bit. Some of the milky stones just turned into rich blue color with a nearly 100% saturation so it's almost black. But some of the milky stones(light blue whitish milky) turn into medium toned Ceylon sapphire blue. The yellowish-blue milky stones just turn into highly saturated blue color.

Thanks for sharing the history of this heating process.

Alex
www.china-sapphire.com


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PostPosted: Fri Oct 13, 2006 4:29 am 
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Hi Alex,
The reason why this or that furnace will work better is about two factor mainly: The first is temperature and the second is the atmosphere in which the stones will be heated. Using this or that fuel, the heat treatment will be performed at different temperature. Then as different fuel are used to heat the stones, the composition of the atmosphere in which the stones will be heated will be different. This will affect in a dramatic way the final color.
As an exemple typically blowpipe or electric furnace are commonly used to heat under oxydizing atmosphere which means that the atmosphere will be rich in oxygen and therefore the blue color in most of the sapphires will not develop. If beryllium rich powder are added then the blue will be even more affected.
Now using charcoal or fuel the atmosphere will be rich in carbon and poor in oxygen. We speak here about reducing condition which are favorable to increase the blue color of many sapphires types like the so called "Geuda".

But if you can control very correctly the atmosphere and the temperature, then you may seriously increase your technology beeing able to adapt the heating process to each type of stone and optimize the results. The Thais and the Sri Lankan are working in these direction respectively for more than 30 and 20 years and are competing to get the best results.

Anyway it is very interesting to see how you are doing and I wish you good luck. But one thing bother me a little bit when I read your posts. You speak about medium tone ceylon sapphire blue as an exemple. If you want one day that the stone from your place get some good prices in the market, you should find way to speak about quality without doing promotion from other sources... Because whatever Shadong sapphires have very few in common with ceylon sapphires and customer should be educated by you guys in order to appreciate their own beauty.
If you dont promote your own stones for what they are, be sure that nobody will do it... An promotion start by names. Anyway I know as I read your post that you try to promote Shandong sapphire and you are doing some good job so far, the thing is that I just would like to make you consider this point...
All the best,

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Vincent Pardieu

www.fieldgemology.org
www.conservationgemology.org

The views expressed here are V. Pardieu’s opinions and do not necessarily reflect those of GIA Laboratory Bangkok (http://www.giathai.net)where he is an employee since Dec 2008.


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PostPosted: Sat Oct 14, 2006 3:29 am 
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Hi all,
Very interesting post Alex and Vincent. I have been too tied up with jobs the last days to check the recent posts.

I know little of treatment processes and rely on a local expert to heat the ones we get done. From what I have seen his process is very much the same although the temperature for our Reddestone stone is less - most other Australian stone heats at about the same temps as described.

I agree with your comments Vincent about marketing and I think Alex would be trying to do this. I think back often over the last years about us calling our business Aussie Sapphire - at times in the early days I often thought that this was silly as Australian Sapphire has had such a bad name but it was done for a reason (to prove a point and try and improve this reputation). We have made terrific gains in our customer base and by simply getting our Sapphire out into different markets described accurately, word does spread.

We cant supply classic Ceylon Sapphire and should stand on our own reputation although at times when you see what some competitors sell as Ceylon it makes you wonder. We have friends Coolamon Mining in Queensland that have fought a private campaign to promote Australian stone for over 10 years but still most local wholesale sellers here choose to go over to Thailand to pick up the bargains.

cheers for now

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