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Originally Posted by 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.
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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.