[Caitlin]

And then to critiques on the thread itself........ I have been looking to see how this thread could be split, but it is a logical progression and your use of the word "dead" pearls was what took it "off track".....anyway KD seemed to be done with this thread.
Actually knotty may have hit on something talking about the "bloom" on nuked pearls. She has had other great ideas that need to go in another thread......
This is what you said

It won't show the damage right away but will "die" before too long if overheated.

If pearls are "alive" then a nuke job may not be good, maybe it boils the conchiolin? If not in water, nuking it will be sure to overheat the pearl....

Foir that matter, how hot is overheating?

[Valeria101]

Originally Posted by Josh

Ooooh. Nuking sounds dodgy for sure. We [...] haven't tried that one.

I don't know anymore if radiation was/is ever used to treat pearls, but what it does to them is no secret. Here's one example resulting from an unrelated experiment carried out by GIA:

LINK



Rumors about some related procedure used specifically to darken pearls have been dismissed 'round here as bogus. And I have yet to find any substantial report elsewhere anyway.

[Caitlin]

Here is a thread on ungluing pearls and the use of the microwave

The pros all seem to recommend attack. Terry says be sure to use water if you use a microwave.

[Caitlin]

Hi Ana
Are you saying that pearls are being radiated for commercial purposes? I though that I heard they are not being radiated for commercial purposes, not that it isn't possible.....

[Valeria101]

Originally Posted by Caitlin Williams

Hi Ana
Are you saying that pearls are being radiated for commercial purposes?

NO.

..........................................

[Caitlin]

Rumors about some related procedure used specifically to darken pearls have been dismissed 'round here as bogus. And I have yet to find any substantial report elsewhere anyway.

I am having trouble understanding what you did mean..... what procedure and what is being dismissed as bogus about it?

[Valeria101]

Originally Posted by Caitlin Williams

I am having trouble understanding what you did mean.....

Two things:

#1. that no reports of irradiating pearls to darken them (or to achieve any other commercially desirable effect) have been reported o this forum - as far as I know. And rummors of uch treatments have been disissed.

#2. that I could not find reports saying otherwise elsewhere.

All in all, nothing covert: I thought that the GIA article would contribute towards answering the question whether irradiating pearls does anything to them. Whether such effects ave been or could be used for commercial purposes, no idea whatsoever. Would be curious to hear more too.

[Caitlin]

Sounds like we have material for a couple of new threads......

[Josh]

More than ten years ago I remember hearing about radioactive freshwater pearls that would make a geiger counter jump all over the place. It was my understanding that nuking was what made the color of those freshwater pearls look like exagerated Tahitians. Have I been living a lie? Some one set me straight please.

[jshepherd]

Originally Posted by Josh

More than ten years ago I remember hearing about radioactive freshwater pearls that would make a Geiger counter jump all over the place. It was my understanding that nuking was what made the color of those freshwater pearls look like exaggerated Tahitians. Have I been living a lie? Some one set me straight please.

Let's try to set the record straight. It sounds like you have heard a story that has an element of truth, but has been passed down too many times to remain intact.

Irradiation does exist. I say "does" very lightly, however, as it was an old practice in Japan, started in the 1960s and continued into the 70s and 80s, but never on a large scale.

The irradiation is done with gamma rays, and only changes one type of mother of pearl - freshwater. It affects the manganese which darkens the MOP. Manganese is only present in freshwater mussel shell, not marine mollusk.

So how does it darken cultured pearls?

With akoya, the bead is darkened, not the nacre. So the color change is actually the bead showing through the nacre. The nacre is still white and translucent, but appears to be dark.

This will not work with South Sea pearls, as the nacre is too thick, not Tahitian pearls for obvious reasons.

With freshwater pearls, composed solidly of mussel nacre, the nacre will darken and typically gray. The longer the gamma radiation lasts, the darker the pearls will become. This was almost exclusively a Japanese practice, however, and more or ended with the Japanese freshwater pearl industry.

There is no radiation danger from treated pearls. That part of what you heard, Josh, was an "old pearler's tale". Referring to Strack "There is no danger that the pearls themselves will emit radiation as a result of the treatment, as the radioactive base element cobalt 60 produces the stable daughter element nickel 60".

[Josh]

Cool, thanks Jeremy. I had to read it twice but will go to bed less stupid tonight. But wait a minute, does that explain the wild colors too?

[CortezPearls]

Originally Posted by Josh

Hi Knotty and Caitlin. Yeah, pearls die from excessive heat. They lose their color, luster and orient. Fifteen years ago on one our first harvests we buffed a few with a polishing wheel. They died months later and looked hideous. I don't know the temperature that needs to be respected but I can tell you that they became too hot to hold in your hand.
Skinning is not hard but you have to go VERY slowly. I could tell you how but then I'd have to change my name, get a nose job and send my family into hiding.

I agree with Josh! And here is a picture to prove it...a "dead dyed FWP". I was conducting some of my torture tests (FWPs make excellent Guinea pigs) and the heating test produced some of the ugliest results: after some 10 days, the pearls produced some "sub-cutaneous" bubbles and they started peeling in parts...nacre was "flaking".

The original pearls looked nice (photo included also) before subjected to the "Heat Tests".

[Caitlin]

Commercial grade black dyed FW pearls often have chips and chunks missing like that. Strack said in her lecture that the black dye makes them more brittle....

[CortezPearls]

Originally Posted by Josh

Cool, thanks Jeremy. I had to read it twice but will go to bed less stupid tonight. But wait a minute, does that explain the wild colors too?

I would also like to have an answer to this question. My information sources told me that some dyes used in China contain oil-based substances and /or metallo-porphyrins. But I do not have any certainty...

[Josh]

So... no answer out there? Us natural pearl farmers want to know.