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 Post subject: Welo (Ethiopian) opal setting
PostPosted: Sun Oct 08, 2017 7:11 am 
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I recently asked my very experienced jeweler to set Welo opals in a ring and earrings. He had never worked with this gemstone before so he was a bit at loss. Welo opals are transparent as opposed to Australian opals which are not. He set it into a bezel with a 100% silver filled backing. In my view this has dramatically reduced the color play of the gemstone. He claims that without the solid silver backing, the opal would look very dull. I did not say anything as I was at a loss. I trust his skills (NB he uses a professional gem setter to place a stone in a ring, earring, etc), but have doubts whether he knew what he was doing in this case.

I would appreciate any suggestion on this matter.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Sun Oct 08, 2017 9:54 pm 
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Your jeweler is wrong IMO.

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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Oct 09, 2017 1:10 am 
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Thank you, Barbra :D


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Oct 09, 2017 3:31 am 
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Transparent Wello Opals benefit from a dark background.
Take a loose stone, put it on a white piece of cloth or paper, and then on a dark one and you will see the diference. Much more colour play on the darker background.
What i usualy do is oxidizing the silver plate underneeth the opal.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Fri Oct 13, 2017 5:29 pm 
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It depends on the stone. Some look great without backing. Others look a lot better with backing, but the backing has to be a dark color, preferably black. I can't think of a single instance where a non-dark backing improved the look of a welo.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Fri Oct 13, 2017 6:44 pm 
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I don't like closed backs on anything because who knows what's back there and it makes cleaning next to impossible.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Nov 06, 2017 11:02 am 
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Personally I like to try it, put the opal on a bright metal backing, then on a frosted backing, then on a black backing. Then try it without and decide what would be best.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Nov 06, 2017 2:34 pm 
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I was just commisioned to make a pair of Gold studs with transparent Welo Opals.
Since i can not oxidize gold, i'll have to come up with another solution.
I'll keep you updated as work progresses.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Nov 06, 2017 2:56 pm 
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Here in the UK we have a platinum solution that gives a really black surface on gold, worth looking for.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Mon Nov 06, 2017 3:08 pm 
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Alan F. wrote:
Here in the UK we have a platinum solution that gives a really black surface on gold, worth looking for.


Is there a brand name? Manufacturer?

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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Tue Nov 07, 2017 5:43 am 
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Used my bottle up years ago and never got another as the fashion passed, but I'll see if I can dig out some info for you.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Tue Nov 07, 2017 2:54 pm 
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I think you are referring to black rhodium.


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Tue Nov 07, 2017 5:30 pm 
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Barbra Voltaire wrote:
I think you are referring to black rhodium.

So it's a plating process, not mere oxidation or similar? I know low-karat gold may oxidize but high-karat's very stable.

I used to use an acid-based liquid of some sort that worked well blackening high-karat gold. It required the workpiece to be heated and was applied with an iron nail. I've lost track of the name and would like to find something similar.

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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Wed Nov 08, 2017 5:21 am 
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It wasn't a plating process, you just painted it on, it seemed to be some sort of electrochemical deposition process, etching out one of the alloying metals in the gold and preferentially depositing the platinum to give the black colour (I'm guessing here, but it's an educated guess).


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 Post subject: Re: Welo (Ethiopian) opal setting
PostPosted: Wed Nov 08, 2017 10:39 pm 
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This is one brand of the stuff you are talking about. Paint on silver and it goes black. Apply with an iron/steel (not stainless) nail or wire, and it will go on black on gold.

https://jaxchemical.com/shop/jax-silver-blackener/

In the past, the 2 oz bottle shipped from JAX w/o hazardous fees. Not sure currently. Rio Grande and others charged the haz fee.

What you want is an antiquing/blackner that contains hydrochloric acid and tellurium dioxide. Several brands/suppliers are out there.

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