There was information in my files when I arrived in 1980, about flourescing
porcelain and clear glass.
Olive Jones' colors for lead glass matches what we find, using a short-wave
light. For clear glass that doesn't flouresce "ice-blue" or "ice-purple,"
we look under the long-wave light. Soda-lime glass appears bright
yellow/green. A lot of glass from the late 19th and 20th century has other
decolorizing agents, and doesn't flouresce (or not as brightly).
Note that this is for glass that is perfectly clear. If it has a yellowish
tint, greenish tint or other color the flourescence may be caused by other
components.
Porcelain, we use the short-wave light. You must first determine that it is
porcelain (translucent, etc.) Bone china appears to have a light (lavendar)
glaze with a dark body, and hard paste porcelain has a dark (deep purple)
glaze and a lighter body.
In our lab, we also sometimes use the short-wave light on questionable
pieces of refined white earthenware. Whiteware and ironstone apear bright
(much like bone china), while pearlware appears dark and creamware appears
dark and somewhat cream colored. This is useful for those mid-19th century
wares that are cream-colored but don't look quite like creamware -- they
flouresce like whiteware.
We use a Raytech LS-88 with both short-wave and long-wave tubes. Note that
results may be different with different UV lights, as different lights have
different frequencies and strengths.
Barbara H. Magid
Alexandria Archaeology Museum
105 N. Union Street #327
Alexandria, VA 22314
(703)838-4399
(703)838-6491 (fax)
www.AlexandriaArchaeology.org
Ben Mortimer
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04/04/2005 03:38
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Olive Jones (Parks Canada Glass Glossary 1989:12) suggests using UV light
to determine the presence of lead in glass. English lead glass will
fouresce ice-blue and demi-lead glass is ice-purple under ultra-violet
light. But as to why is does this, Jones only says it is a "complex
phenomena".
Ben Mortimer
National Parks and Native Sites Archaeologist
Parks Canada, OSC-Cornwall
Denis Gojak
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04/04/05 03:17 PM
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Hi all
A bit of a trivia question.
Attached is a link to Nature News, the chatty gee-whizz stories from the
august journal Nature. This one is about a materials scientist who is
creating a reference collection of unusual materials [many weird
synthetics]. It contains the following paragraphs:
'Miodownik trawls the globe in search of additions to his collection. On a
recent trip to Australia, he found himself in the remote uranium-mining
town of Broken Hill in New South Wales. He started hunting through antique
shops there to find a special type of glass.
'Miodownik explains that in the early twentieth century people thought that
radioactive materials had beneficial health properties. For this reason,
they manufactured glassware containing uranium, especially in places such
as Broken Hill that had an abundance of the element.
'In the Australian antique shops, Miodownik flashed an ultraviolet light on
various glass pieces to find one that glowed, a sign that it contained
uranium. When he found a bowl that did just that, he brought it back to
London and added it to the library.
[full link - http://www.nature.com/news/2005/050328/full/050328-5.html]
Apart from the small matter of Broken Hill mining silver, lead and zinc and
no appreciable uranium, nor being a notable decorative glass manufacturing
centre, I was wondering from some of the many glass gurus on the list what
added elements cause flourescence such as described. Was Dr Miodownik's
bargain hunting futile?
cheers
Denis
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