Sleuthing nacre thickness and treatments

[Valeria101]

Here's one common scenario: you (enthusiast but novice pearl buyer) got those pearls in the mail... They look sort of nice all by themselves. But there is no independent grading, and no knowing what you've got until you know where that nice look comes from: plastic coating? dye? mother mollusk? and how long is that precious sheet of nacre gonna last before peeling away, cracking, drying out... Some may even want to know how much 'real pearl' is there as opposed to MOP backing, just for the sake of it.

I don't have that many tricks: candling, looking for surface details with a jeweler' glass hoping to distinguish chemical dehydration, dyes and bleaching. Not that I'd swear by the results!

What are our tricks? Other then sitting on the edge of the pond while the pearls are hatching - that doesn't count.

What o look for?

 

[IowaCamper]

Is there any way to figure out exactly how deep nacer is on pearls? What if someone says very thick and somebody else says 1mm?

 

[Valeria101]

Is there any way to figure out exactly how deep nacer is on pearls? What if someone says very thick and somebody else says 1mm?

For akoya 'very thinck' IS 1mm...

X-Ray is the legitimate thing to do.

Some advocate for a less precise method: placing the pearl against very strong light... I am not sure if that works for me though. At least not on all pearls. I hope someone else chimes in here.

 

[Perle]

For what it's worth, someone claimed to have figured out a way to measure the nacre thickness of cultured pearls without an x-ray (apparently, it was inspired by candling) in a patent that issued almost 15 years ago. I don't know what happened after that, and a quick look around didn't turn up any devices based on it.

As far as I know, the most reliable way is x-ray. The above inventor said one could measure nacre thickness by looking down the drill hole (if any) with certain equipment, but since the labs use x-ray I'm guessing it's either easier, more accurate, or both.

IowaCamper, if a seller says the nacre thickness is 1 mm (I assume you mean each side), they should be able to prove it. As Valeria101 noted, the most reliable way appears to be x-ray (by a reputable lab).

Jeremy, if you are following this thread, do the Hanadama certs list nacre thickness measurements above .6 mm? Or is .6 mm the highest, meaning "at least .6 mm," with no more specific measurements given?

Perle

 

[Valeria101]

For what it's worth, someone claimed to have figured out a way to measure the nacre thickness of cultured pearls without an x-ray (apparently, it was inspired by candling) in a patent that issued almost 15 years ago. I don't know what happened after that, and a quick look around didn't turn up any devices based on it.

I've tried a bare-bones version of the device - pearl set in round hole in opaque cardboard (a book binder's kind) close to the pearl diameter diameter and the strongest light I could find behind the pearl. Some do lit up and one can see the dark nucleus like a yolk But you need thick nacre otherwise the foil-thin layer blends in with the shadow produced by the edge of the cardboard around the edges of the pearl.

Using an old photo camera shutter (old= '40s) to hold the pearls so that there is no overlap between the edge of the holder and the pear seems to work better, but you'd need a customized device - my shutter kept light at bay but the thin, friction-less blades make the operation hair-pulling tedious.

Besides, I didn't care what happened with the pearl exposed to bright light and heat from the source - it those were fine pearls, that would change, wouldn't it.

And if the difference from 'bad' to 'fine' nacre thickness is tenth of a mm just about any method that ain't super precise isn't going to matter anyway.

Oh well...

I would imagine that tricky difficulties like this along with the lack of interest to disclose nacre thickness stopped any attempts to develop a portable, buyer-friendly device to estimate nacre thickness.

If it isn't even common to disclose nucleated vs. non-nucleated status (say, fro freshwater)... what could be the motivation to go one better and disclose nacre thickness?

Seriously! Not a rhetoric question.