Topic: Whitish color under short wave UV

[Mary D]

Hello everybody! I am a new member that just joined today.

I have a 4W handheld shortwave UV lamp (254nm) that gives a bluish color on known lead crystal, such as Waterford.
I sometimes get a whitish color with old glass and I do not know how to interpret this. Is this whitish color considered an indication for the presence of lead? What is causing this whitish color?
Thanks in advance for your help.

[KevinH]

Hello Mary, welcome to the GMB.

That is an interesting question but it is is one that is not easily answered.

I have used longwave uv (peaking at 365 nm) and shortwave uv (peaking at 254 nm) for examination of paperweights (mostly British) and for interest with general "decorative Victorian", a few earlier and a few 20th century clear and coloured items. I have not noticed anything that reacts under shortwave as "whitish".

For many non-lead glass items (that is, not of the 24-30% lead range), I have seen a shortwave "dusty grey" or perhaps a "dusty green" reaction and sometimes a reaction that looks "silvery", but not particularly "whitish".

All of my uv checks have been made with a mains powered dual-lamp "mineral light". And even with that unit, the uv reaction can appear as different shades of a colour depending on the distance between the lamp and the item. I have very little experience of reactions with a low-powered unit.

Is this whitish color considered an indication for the presence of lead?

No, not in my experience. For my own items, where there is an obvious shortwave reaction for "lead glass", the colour seen is a shade of blue. A blue reaction is known, scientifically, to be a standard reaction for lead-based glass (although apparently, if there is a very high percentage of lead in the mix, then the uv reaction disappears).

My own uv checks have only covered a couple of likely American items. Perhaps some American glass mixes have a shortwave uv result that I am not aware of.

[Mary D]

Thanks a lot Kevin for responding to my question.

I read somewhere (might be here on this forum) that a whitish color is still an indication of the presence of lead in combination with a high % of another element (I think manganese).

A site in the US that sells EAPG says this  “To determine flint or lead glass, which generally glows "white" or "blue" or even "yellow" depending on the percentage of lead in the glass and the impurities mixed therewith, …”

http://www.patternglass.com/blacklights.htm

I researched the Internet and the only conclusion that I came up with for sure, is that the bluish color is indicative of the presence of lead. It seems that these other colors are not researched or discussed much.

[KevinH]

It seems that these other colors are not researched or discussed much.

Good conclusion.