Mussel nuclei that size , if procurable, would be very expensive. I think these are the nuclei Strack talked about, which appear to be in production now. The nucleus is made of shell powder and a chemical glue formulated specifically for this use. It that yields a perfectly smooth surface that nacre loves to coat.
Hi all- sorry about my absence on this very interesting topic, but I'm Anti-Internet on the weekends
Caitlin- I haven't heard about much progress in that area- Strack is a teensy bit outdated in terms of manufactured nuclei info. However, I do know that bironite had some very interesting promise, and that there are a few companies out there working with vapor encapsulated nuclei which is a coating around the bead that allows for lower quality beads to be used in Akoya culture (which would be fabulous since the American mussel shell industry does not really manage their resources). However, I have not heard that they've taken the industry by storm yet- I wonder what's the holdup?
There is no farming or husbandry done with the American pig toe mussel (et al) since the best specimens that fetch the highest prices are about 15 years old- many salvagers don't think that farming the mussels is worth the time, effort or money- admittedly expensive- and rely on their dredging methods instead. This means that every year, the best mussel stock is not replaced in any meaningful way, and prices for creamy white, unblemished nuclei is rising. To keep Chinese Akoya farming competitive, bead costs must be kept low and they are keeping an eye out on developments in this area since the beads are becoming quite expensive. I venture this is another reason why Josh is using his margaritifera shells for nuclei- it's a great way to duck the cost of buying the little suckers in bulk, and with Tahitian pearls, you don't have to be so concerned with whether there is any discoloration on the bead. But they still need to be perfectly round and smooth, since the outside nacre layers will reflect the imperfections found on the bead.
I very much think that T. gigas is used in a majority of the Fire Balls- I concur on that count. I don't really think that China is concerning itself too much with CITES at the moment, and they do farm T. gigas anyways, since they are considered a delicacy, and many South-East Asian cultures enjoy the flesh.
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since I am not a physicist, and the earlier question was an excellent one, so I decided to do some research to further clarify my ideas, and to expand the discussion a bit more.
The relationship between specific gravity (or density) to the thermal coefficient of expansion is dependant upon the specific material used (in our case, we're mainly speaking about freshwater shell) vs. measurable outside temperature changes. The reason is that during heat transfer, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bond. (source: Wiki)
A material's specific gravity or density is a weight to volume comparison, and it is measured against water: a material greater than 1 water atm (4 degrees celcius aka 39.2F- this is the preferred measurable temperature universally as this is when water has it's greatest density) will sink, a material less than one atm will float. Materials that are 2.7 or less are considered light materials, any material weighing 4-4.5 are considered dense and heavy. If the bead measures 2.7 SG, it is 2.7xs heavier than water.
The coefficient of thermal expansion as it relates to Freshwater shell material depends upon the temperatures the material is subjected to. I would think that the denser a material is, the slower it heats and cools, however you are placing more strain on the materials' structure and will have a higher chance of damage the more stress the material is subjected to; imagine water freezing in a crack of a boulder over a period of years- eventually the boulder shatters as it's solid, frozen atomic structure does not handle being forced by the presence of water and ice very well...
As we know, water, gas and solids all have varied reactions to temperature. In the case of T. gigas nuclei vs. FW mussel nuclei we'd have to do an experiment, since very little information exists on the subject (at least that I could find... perhaps us pearl nuts are the only interested parties lol). In addition, I was not able to locate the T. gigas' SG anywhere, and I googled and googled and googled. While the content of the pearls' nacre in both cases is the same (CaCo3), the saltwater clam shell and freshwater mussel shell have varying trace minerals that would need to be observed and subjected to strictly controlled temp changes to see which bead cracks the nacre first. Who has a lab?
