I've been interested in the metal components of glass formulations for quite some time. The glasses that reduce to give us such nice metallic finishes are of particular interest to me so I've looked into it a bit when the opportunity has allowed. Encasing will immobilize any reduced metal but a metallic surface exposes the reduced metal to wear. Below is an example of an exposed surface.
These are a few images of Rubino, aka Gold Ruby or Ruby Gold - all three have the same catalog number. These are paddles of the glass formed and reduced on the ends of rods. You can see that there are some color differences between the batches and there is a nice metallic sheen on the reduced ends.
These were taken with a scanning electron microscope (SEM) operating in backscatter mode. This means that areas of higher atomic number will appear to be brighter than lower atomic number areas. The first image is a reduced surface at an original magnification of 500X. The scale bar in the corner is 20 microns.
The second SEM image is the same glass as seen at 10,000 X, the scale bar is 1 micron. Each bright spot is a tiny bit of reduced metal on/in the surface of the glass - they're around 250 nm in diameter. For comparison, Staphylococcus bacteria on your skin are about 4 times bigger.
This is the X-ray spectrum taken from the area of the little square box in the first SEM image. The big peak marked Pb represents lead. There may well be some gold chloride in the glass for color, but most of the metal on the reduced surface appears to be lead.
It is a minute amount of lead, fair enough, but in light of the recent issues with the CPSC and lead content in products I'm not sure you would want to discount it totally. It is a surface coating, even if it's pretty thin (about 1 micron, more or less). I don't see it as a major health hazard but at the same time it pays to be informed about materials that you use. This is why I keep telling people to be sure that the name of a glass truly indicates the content or it it's a description of the color that it turns. Silver (*.*) and gold (*.*) may or may not be real elemental silver and real elemental gold.
Robert