X-Ray Microanalysis of Art Glass
Silver plum glass
remained very similar in color to the unheated rod when melted in a neutral or slightly reducing flame. Increasing the oxygen in the flame brought a bright silver surface to the glass. Te EDS X-ray analysis showed manganese and zinc on this surface (Figures 6A and 6B). Te Kugler Gold
Figure 4: The left bead shows the red and gray reduction colors produced on the surface of Effetre 236 Dark Turquoise glass when exposed to a reducing flame as compared to the color of this glass when melted in a neutral flame.
Brown developed a bright silver surface. Careful manipulation of this glass in the torch flame can result in colors ranging from dark gold to bright silver. Te SEM showed a surface similar to that seen on the Rubino glass, small highly backscattering dots on a darker surrounding surface. Te EDS X-ray analysis indicated the presence of lead as well as silver on these surfaces (Figures 7A and 7B).
Discussion Te visual appearance of these reduced glasses would
suggest to the layman that the surface might, indeed, be either silver or gold. While both of these elements are heavy metals, they are considered safe for skin contact and are prized as materials for jewelry making. Copper in both pure and alloy form is oſten used as a jewelry metal as well. Manganese and zinc
Figure 2: (A) Scanning electron micrograph in BSE mode showing bright islands of material on the reduced glass surface. (B) X-ray spectrum indicating the presence of lead along with silicon on this surface.
these features indicated the presence of lead with silicon in the surrounding glass (Figure 2). Ivory glass remained a pale tan color when melted in a
neutral flame. When exposed to the torch plume downstream from Rubino glass melted in a hot neutral flame, the Ivory glass turned a streaky metallic gray, typical of the reaction of this glass with metals (Figure 3). Tis process is commonly known as “fuming” and is oſten used to create a metallic surface on glass using pure metals such as gold or silver. Dark Turquoise glass remained the color of the unheated
Figure 3: Beads made from Effetre 264 Ivory glass. The left bead was produced in a neutral flame and then exposed to the torch plume from a melted gather of Effetre 456 glass. It turned silvery gray as compared to the normal color of this glass when melted in a neutral flame with no exposure.
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rod when melted in a neutral flame. High heating in a slightly reducing flame produced a red color on the surface of this glass (Figure 4). Some metallic silver gray areas were also seen in areas exposed to less heat. Te SEM showed small crystalline structures on the red surfaces, and EDS X-ray analysis indicated the presence of copper and zinc. Higher levels of zinc were recorded in the metallic silver gray areas (Figures 5A and 5B).
Figure 5: (A) SEM image (SE mode) of crystallization on the reduced Effetre 236 surface. (B) X-ray spectrum indicating the presence of copper and zinc as well as silicon on the glass surface.
www.microscopy-today.com • 2010 September
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