Author Topic: black light etc.question.  (Read 1401 times)

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Offline dreamticket2

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black light etc.question.
« on: July 08, 2006, 06:28:07 PM »
Our local Pound Empire (UK) shop is selling black light pens with invisible ink for the children to write secret messages!  :idea:

As £1 seemed reasonable to experiment I tried the light  on one ot two of my Strathearn / Vasart  miniature pwts and some did have a green florescence in the glass.
I am not sure about the wavelengths that the experts use but would love to know more. Jean
 :wink:


Offline KevinH

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black light etc.question.
« Reply #1 on: July 08, 2006, 11:25:54 PM »
Hmmm, all Vasart / Strathearn weights should show green, even with a "pencil" type UV "black light". But it does depend a lot on the power of the UV light and the degree of darkness under which the test is made.

Also, a UV reaction can sometimes appear weaker in a weight with a majority of clear glass when compared to an item from the same maker but with proportionately lesss clear glass. Logically, I don't really think this makes sense as surely the reaction ought to be the same for the same type of glass? But I have seen this effect. Perhaps it means that for some items, the clear glass was not actually mixed to the exact same formula all the time? It's one of the things about UV testing that I find fascinating but logically and technically challenging!

If your weights were checked under a more powerful lamp, my guess is that they would indeed all show a good and quite bright Green colour - uless, of course, this that don't are actually not Vasart or Strathearn.

Perhaps you could post some pics (or email some to me)?
KevinH


Offline dreamticket2

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black light etc.question.
« Reply #2 on: July 09, 2006, 08:42:16 AM »
Thank you KevH, I will try to get the pics organised.
The problem will be keeping the light switch pressed on the pen with one hand and taking a picture in focus- will have to try and find a stand for the camera.
Will do my best.
Great information.:D
Appreciated.:D
jean :D


Offline KevinH

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black light etc.question.
« Reply #3 on: July 09, 2006, 07:11:04 PM »
Sorry, Jean, I should have explained my request better ... I meant ordinary pics of the weights, not the UV reaction (for which I am very much aware of how difficult it can be to get good images).

With standard pics of those that don't show Green UV reaction for you, I may be able to say whether they are Vasart / Starthearn or not, or perhaps some other maker. And what would be very useful is to also show slightly angled pics of the bases of those weights as that can give extra and important clues.
KevinH


Offline wrightoutlook

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gotta get one of these "pencils"
« Reply #4 on: July 10, 2006, 01:08:44 PM »
I've got to find one of these black-light "pencils."

What I'm really wondering is this: Is there a guide to black-light results? Either in a book or on the web. Has anyone prepared a list of what to expect when using black-light on a paperweight; what the glass reveals under black-light? Etc.

Offline Frank

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black light etc.question.
« Reply #5 on: July 10, 2006, 01:35:51 PM »
There are extensive discussions on this board:
http://www.glassmessages.com/index.php/topic,1263.0.html

For others try this search: UV testing
Frank A.
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Offline KevinH

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black light etc.question.
« Reply #6 on: July 10, 2006, 03:01:31 PM »
I know of no "Guide to Blacklight Results". But in some paperweight books, general comments have been given for such as antique French weights and also for 20th century Ysart items.

But ...

Paul Hollister Jr, discussed UV test results in his 1969 book, The Encyclopedia of Glass Paperweights pages 285/6. He pointed out that specific UV colours had, by then, been stated for a range of antique French weights. However, as result of further tests under more strictly controlled conditioned, he concluded that there were variations. For example, he said that some people had reported "peachy pink" for Baccarat weights whereas the previously defined colour had been said to be "deep blue".

From my own tests of limted numbers of weights, using both longwave and shortwave uv (only the longwave "black light" was used back in 69) I concur with Hollister's reservations. There are variations which confound and confuse attempts at setting down a definitive uv colour range for a given maker's weights.

What I have found, though, is that Green is a standard black light uv result for clear glass from centuries past  to the present day (I have even checked some 18th century English ale and wine glasses). Basically, it seems that standard "soda glass" will fluoresce with a shade of Green and so will much of the "lead glass". So a black light uv test can't really prove anything - other than that the glass "glows nicely" [and perhaps that a really strong yellow-green reaction could indicate the presence of uranium oxide in the batch].

In my article Identifying Paul Ysart Paperweights (see The Glass Museum pages: http://www.glass.co.nz/ysart.htm) I set down a table of uv results that updated those in the Scottish Paperweights book. I also added some brief caveats as I had noted differences in the results for some weights. That was in 1999/2000. Since then, I have seen further variations in shades of colour, although in the main, my table of results is still ok for general separation of Ysart items into the wider periods of their making.

I firmly believe that uv testing is a tool that can aid the identification of paperweights, but it cannot usually be used alone to state an attribution.

I would like to be able to test large numbers of positively attributed weights of various makers. But this is a very difficult thing to achieve, even within a paperweight club. However, if there is anyone in the UK reading this message who has a large collection (at least 100 would be useful) of positively identified weights from a given maker, preferably also with positive dating information, I would be happy to arrange a visit to check and tabulate the uv results.
KevinH

Offline wrightoutlook

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THE BULB BRIGHTENS
« Reply #7 on: July 10, 2006, 03:23:46 PM »
Enlightening post KevH and I am much enlightened.

Offline dreamticket2

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Re: gotta get one of these "pencils"
« Reply #8 on: July 13, 2006, 08:50:14 PM »
Quote from: "wrightoutlook"
I've got to find one of these black-light "pencils."



The 'Magical pen with Blacklight ' -includes 4 spare batteries.
 Marketted in the UK by JENSAN  Jm-6-1954.
Jensan Marketing Ltd UK TF 2 7NA
Jensan Marketing Ltd
01952299600  

Deer Park Court , Donnington Wood , Telford , Shropshire  TF2 7NA

Hope this helps.
Jean

 

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