Topic: Using UV light

[Antwerp1954]

I recently bought a cheap uv light. On soda glass it gives a yellow iridesence but nothing grom lead glass. The second uv light gives a light blue iridesence on lead glass and yellow on soda glass.

Has anyone any info, or can point me to any info, on the use of uv to identify glass?

[oldglassman]

Hi ,
          Looks like you have what you need in your lamps . as you have seen lead will glow a slight blue or white and soda/potash will be a yellowish colour , there will be slight variations between glasses because of different compositions in both lead and soda/potash but basically you have what you need , the best place to look is at the foot rims and bowl rims , see attached pics , 1 is lead 1 is non lead , probably potash glass.

cheers ,
                Peter.

[Lustrousstone]

A very bright green glow from either will mean uranium but your glass must be coloured not colourless. A fuzzy yellow green (even slightly orangish) glow (as Peter's RH glass) from clear or coloured glass is likely to be manganese but with some glasses it can be quite a bright glow, just not as bright and green as uranium.

[Paul S.]

The degree of reaction obtained when shining a u.v. torch at uranium glass, is dependant, apparently, on the wavelenghth of the u.v. light it emits, and this is rated, usually, in nanometres (nm).
It's the longwave range  - often called blacklight - that's needed for making the glass glow to best effect, and this is apparently when the the nm figure is somewhere between about 365 and 400 nm.
Torches used for checking banknotes are somewhere around the 465 figure, and those sold for use on glass are rated at about 385 - 395 nm, and apparently best results for uranium glass are obtained when the figure is about 395 nm.

All of which is a roundabout way of saying that it's possible that cheaper torches, having perhaps a figure of less than the above, might well not give a hoped for result - or perhaps a more limited result.           Some less expensive torches can give a noticably strong blueish effect when used, which might affect the results of photography, although they are more than adequate to indicate the presence of uranium in glass.

In addition to the more common decolourant manganese, there are others such as selenium and cadmium which can fluoresce yellowy oranges, and confuse the issue.             There have been many chats on the Board over the past few years re this subject - many written by knowledgable people - and well worth reading  -  I believe Christine has been involved in many of these

For a tenner or less you can buy a half decent u.v. torch - although I believe there are these who swear by the key-ring sort.