Pearl Dust

[SteveM]

These Roman or perhaps even pre-Roman artifacts were found in the vineyards of a Bekaa Valley (Lebanon) wine producer we met a number of years ago.

The glass is a lachrymatory bottle (tear vial), and according to someone supposedly 'in the know', the glittering surface is ground pearls (nacre), or pearl dust. I've just begun my research on this, pearl dust coming up as an additive to cake frostings (for metallic lustre) or in the case of real pearls, as a dietary 'supplement' (Mikimoto famously consumed a pearl a day, and Cleopatra desolved a huge one in a glass of wine).

Perhaps there are forum readers who can already enlighten us on this application of our beloved subject?

Steve
Seattle

 

[Raisondetre]

As far as I am concerned, pearl dust is calcium carbonate, probably with trace minerals and metals. It'd be good as a calcium supplement in osteoporosis (Caltrate is calcium carbonate anyways), but as far as clinical trials are concerned, there is no real evidence that it's truly beneficial to health. In traditional Chinese medicine or TCM, it is used as a "cooling" medication for those with a "heaty" constitution. I prefer to think of it as a pro-inflammatory state of health, though pearl dust does not have any proven antioxidant properties that would neutralize free oxygen radicals produced in the inflammatory pathways to produce such an effect.

Topically, pearl dust is a good blotting powder for oily skin.

However, some polluted waters will produce pearl containing traces of mercury, lead or other toxic metals, so I do not recommend the use of it. I do take a vial once in a while for fun since I am Chinese, but I am strongly against it for children. It's popular in TCM for kids with fever. But as far as Western medicine is concerned, I do not see the therapeutic value of it.

Not sure pearl dust is cheaper than formal calcium supplements. Note that if you do take calcium you need to take vitamin D as well.

Sorry, I thought this was just a general discussion on the applications of pearl dust. Did not realize you just wanted the esthetic applications. My apologies.

 

[SteveM]

Refocusing on the pearlescence of the Roman artifact: Appears to be abalone. Any ideas? Any modern examples? Is this a lost art?

Steve
Seattle

 

[nlerner]

This is most likely a piece of ancient glass.


From "The Virtual Egyptian Museum" Glass Iridescence
The iridescent effect that so often enhances immeasurably the beauty of ancient glass was not planned by ancient glass artisans. Instead, it is the combined result of weathering processes and the properties of light. The rainbow effect you commonly experience in daily life, such as on soap bubbles or drops of oil spread on water, stem from the same action: light bouncing on a extremely thin transparent film.


When a glass bottle is new, there is no such thin film. The wall of the bottle is homogenous. But ?as glass is exposed to water in its burial environment, some of its [chemical] components can be dissolved by the water and carried away (leached out). This generates a thin surface layer of glass that has a different composition that the undegraded bulk of glass. Often, there is a think layer of air between the corroded surface and the bulk? (Bez?r 1999).


When ordinary white light strikes the bottle, some of the rays bounce off the top surface of the thin film, and some go through the thin film and then bounce off the glass-air interface between the thin film and the underlying glass. When the rays coming back from the bottom of the thin film reemerge into open air, they combine with those that simply bounced off the surface. But since they have been delayed by their additional travel, their waves are no longer in phase (in synch). When these two streams of out-of-phase white light combine, some of the wavelengths cancel out (and therefore those colors disappear), and other wavelengths are reinforced (and therefore those colors become very intense), thus turning white light into vivid random colors.


Glass artists of the late 19th Century, such as Louis Comfort Tiffany, admired the iridescence of Roman glass, and devised ways to produce it deliberately by placing the glass piece while still very hot in an oven filled with vapors (tin and iron chlorides) that would alter the surface and create a thin film of different composition, yielding an iridescent effect that did not require a thousand years to develop.


A more thorough technical discussion of the phenomenon by Aniko Bez?r of the University of Arizona Department of Materials Science and Engineering is available from
http://www.u.arizona.edu/ic/mse257/class_notes/iridescence.pdf

 

[SteveM]

Great work, and from so close to the source!

My quick breakfast research today hit a tantalizing roadblock in the Google search below ('server no longer exists'?aargh!).

Also posted is a 19th-c German Pearl Glaze demitasse and saucer.


Steve
Seattle