Denis, A few of the responses to your inquiry touched on the physical nature
of fluorescence and why we see certain colors when UV light is absorbed.
The answer is related to wave lengths and energy of light and is not so very
complicated.  As I understand it, when UV light is aimed at glass, it may
excite the electrons in the substance in the glass that absorbs the light
for a tiny fraction of a second.  In the process, a little bit of the UV
light energy may be lost, often as heat.  As a result, the light we see is
of lower energy and a different wave length.  Visible light is of lower
energy than UV light explaining why we may see colors under UV illumination
of glass.  Depending on the nature of the absorbing molecules in the glass,
more or less energy of the UV light is dissipated resulting in different
wave lengths reflected & different colors seen.
Allen
----- Original Message -----
From: "Denis Gojak" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, April 04, 2005 3:17 PM
Subject: Glass that flouresces


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