Fluorescence

Maria Brunskog <curare.brunskog [at] spray__se> writes

>>On microscopic examination of cross-sections sampled from aged,
>>japanned surfaces on furniture, a bright and saturated red
>>fluorescence colour has been observed. The light was in the lower
>>UV-range, 330-390nm. At a higher UV-range 430-450nm the fluorescence
>>was not visible. The red colour (like good quality wine) has been
>>interpreted as silver. I would appreciate any comment from anyone
>>with experience of metal/silver fluorescence, either from metal
>>foil or powder incorporated in lacquer media.
>
>I do not know what silver metal would look like under these
>conditions; however, I have not seen this in examinations of metal
>objects in ultraviolet light. Mineralized silver might have a
>characteristic fluorescence. As I recall cuprite (copper oxide)
>appears bright red in uv light.  Madder (red lake) also  fluoresces
>a bright red under ultraviolet light. Could a red glaze have been
>applied over a metal foil?

Metallic silver has the peculiar optical property that causes it to
become totally absorbing in the UV at 330 nm--this is called its
"plasma edge." I am not familiar with the fluorescence of silver
metal oxides, but I would doubt that you are seeing fluorescence
from a silver metal foil--in the near UV.

M. Susan Barger, Ph.D.
Department of Earth and Planetary Sciences
University of New Mexico
Albuquerque, NM


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                  Conservation DistList Instance 15:1
                  Distributed: Wednesday, June 6, 2001
                        Message Id: cdl-15-1-003
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