Glass Message Board
Glass Identification - Post here for all ID requests => Glass => Topic started by: krsilber on June 01, 2008, 12:26:18 AM
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Here in the US the use of a UV light on glass is something of a controversy. Some people say they are good for nuttin', others are under the impression that if something fluoresces, it must be old. Personally I think they can sometimes be used as one tool for identifying and dating glassware IF they are are used knowledgeably. Plus glowing glass is just kinda cool.
Anyway, I'm seeking to expand my knowledge, and I'm asking your help. I'd like to know if British cut (or engraved) crystal glows, and if so, what color. I've heard French crystal doesn't glow, but if possible it would be nice to have evidence to that effect as well. If you have either, I would much appreciate it if next time you got out your UV light you could take a look and report your findings in this thread.
If you don't know where your cut stuff was made, post it and I or someone else may be able to help.
If anyone has seen Continental cut glass from the 30s or later glow, I'd be interested in that, too.
Thanks much for your help!
PS - I once sat down with a sampling of my glass from various places and recorded fluorescence color. If anyone is interested I can try to track down my notes and post them.
PPS - If anyone wants to discuss any aspect of UV-reactive glass in this thread, that's dandy. If it glows, it's on topic! ;D
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FYI France is the only country where crystal is legally defined by its refractive properties rather than its constitution. There are dozens of different cristalleries, each having their own formula, so all varieties are found. The only sensible use of UV in crystal is to compare a known piece to an unknown one. And even then, use disclaimers profusely.
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FYI France is the only country where crystal is legally defined by its refractive properties rather than its constitution. Interesting. There are dozens of different cristalleries, each having their own formula, so all varieties are found. The only sensible use of UV in crystal is to compare a known piece to an unknown one. But even this can be problematic if the item in question was made over a long period of time since glassmakers' formulas changed over the years. And even then, use disclaimers profusely.
I'm aware of the drawbacks and constraints of using UV, which is why I say it must be used knowledgeably and only as one tool among many, if at all. The problems arise when people start to think UV is an answer, rather than (potentially, in some cases) evidence.
In the US it is sometimes used to assess whether ABP-style cut glass is fake. For instance, no ABP fluoresces pink in longwave UV, but fakes sometimes will.
A friend of mine has a piece of Straus that doesn't fluoresce. As I understand it the same pattern was made over a period of years, but before a certain date was called one thing and afterwards another (ABP is a PITA!). Since hers doesn't fluoresce she was able to determine it was the earlier version, made on an imported blank. That's a brief summary and there's other info that I'm omitting, but it's one instance of a legitimate use.
Much of my Bohemian glass fluoresces a dirty pale orange color that I've never seen in American glass. That doesn't mean no American glass glows that color, but if I had an unknown piece that did I would look in the direction of foreign before American.
At this point I'm just trying to gather data; I don't plan on using the results of a few pieces of glowing glass to extrapolate and make generalizations - that would be a misuse of it.
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Kristi, you really must state the "rules of the game" to get any meaningful data for this type of analysis. As you have said in response to Ivo, you are aware of many of the problems, such as the fact that a company may have used different batch over time that reacts differently under UV. But other folk may not know these things and therefore, without knowing the "rules", results could be (unintentionally) distorted.
Also, your request asks aboout "glow" under "UV". But what is meant by "glow"? Some results may show a weak reaction that many people would argue is not a "glow", but which perhaps should be taken into account just as much as something that has a bright reaction.
And do you only want longwave (blacklight) results?
I could try to provide some info for items I have - maybe with photos (?) - but without, in most cases, knowing the actual dates they were made, will it be useful?
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Kev, you're right that I wasn't very specific about the kind of information I'm looking for. Partly that's because I didn't want to scare people off, making it seem too "scientific" for them to be able to help out. The other part is that as far as English glass goes, I'm starting from scratch myself. The only cut (engraved) piece I have is mid-20th C. Webb, and it doesn't fluoresce. Mostly I'm asking about this out of curiosity; if there are any generalizations possible, all the better, but right now I'm more in the exploratory stage.
There is a common statement in ebay listings for ABP along the lines of "it fluoresces greenish, confirming it's ABP." Of course this is nonsense, but it would be nice to be able to say whether glass from elsewhere and from what periods also fluoresces greenish. That's one objective.
As far as dating goes, I think the best I can hope for is narrowing a piece down to a period. From what I understand there is in English cut crystal a brilliant period and a Regency period (is there something inbetween?), and then the stuff that came after. If people have earlier pieces, that's great, too. Since these are based on the style of glass I think it might be possible to make a decent guess, anyway, what is what. Though I don't know it to be the case, I expect glass made after about 1930 give or take a couple decades not to fluoresce greenish since manganese as a decolorant was phased out around then by many glassmakers.
If people are up to posting photos of the pieces they look at (under normal light), that would be excellent! I don't want to turn this into a pain for anyone, though...there's the ideal information, which is nice and specific, and there's the rest. If the data are ever subject to any kind of thorough treatment (if that's even possible), they would be weighted accordingly.
Down to specifics (the "rules of the game" ;)).
Colors - lime green, apple green, pink (kind of fuschia really), "electric" bluish, silver/white, orangish, yellow. These are the colors I've seen under longwave UV. There may be others.
Tone - pale, medium, or deep. This is like the difference between a light pastel yellow and a lemon yellow, and is separate from...
Strength of glow - weak, medium, strong
Date - as precise as you can get, but a range or a ??? is fine, too, though in that case please post a photo.
Maker, if known.
Country/region of origin if known and maker is unknown.
That's the ideal, but folks! don't let it overwhelm you :). If you wish to contribute, please do even if you don't know whether something is lime green or apple green, pale or weak. Some of these measures are subjective and are only possible to judge when comparing multiple pieces of glass or with experience.
The colors I listed are for longwave UV; if people have shortwave UV lights, that would be great information to have, too. Gary Baldwin in Moser Artistic Glass says that using a combination of shortwave and longwave UV he is able to differentiate among Bohemian "crystal," Venetian "crystal," and central European lead crystal from the mid to late 19th C.
Thank you for even reading this long post! I hope this ends up interesting others as well.
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Checking some bits of uranium glass yesterday and noticed a clear glass candle stick reacted, so checked some more pieces, some did and some did not.I have never known this to happen before it has always glowed purple or bluish, could it be contaminated or was uranium or some other chemical added to the clear glass for some reason. Is it rare and can the makers be identified by the pictures, would it help if you knew who made them was it standard practice. I know some Scottish paperweights glow but i think this is crystal glass. I am at a loss all help and input greatly appreciated.
p.s in plain English please
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10107
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10105
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10111
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10113
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10109
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10101
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10114
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10110
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10112
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10115
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10108
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10102
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10103
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-10104
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See my reply to your separate post Bungie.
PS Your pieces are all pressed and not cut
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Interesting discussion.
I gave up on my UV light, I think I need a new one.
English pieces of cut glass, I have no success in changing color under the light.
I did have a Clark piece that the color was a deep yellow and I have not seen any other glass have the same color.
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I hope Christine (lustrousstone) doesn't mind if I copy her comments to Bungie60 in this thread. Her great explanation might help others reading it in the future. (My additional comments are in blue.)
The greenish glow in your clear glass (including paperweights) is caused by the presence of a manganese compound. This was very commonly used as a decolorising agent; clear glass often naturally has a greenish colour cast like Coke bottles. Manganese has been called "glass soap" and has been found in glass of ancient Rome. The green color of "bottle glass" is due to iron impurities in the sand used to make the glass; it can also be seen if you look at the edge of modern plate glass. Other decolorising agents are generally used instead these days.
This yellowish green glow can be found with other glass colours, including green, so unless your green glow is really really bright green, you can't attribute it to uranium. Uranium always glows the same shade of bright green, no matter how little was used. The glowing just looks a little diluted.
This is the sort of glow uranium gives, your photos are excellent examples of the glow manganese gives in glass of any colour I haven't seen it in any color but "clear" colorless glass - has anyone else?
Managanese is also what causes clear glass to develop that greyish or purplish tinge (or even a very bright purple tinge but not in the UK, not enough sun or UV rays). The ultraviolet light causes a chemical reaction that turns the manganese compound from a colourless one to a purple one,
Manganese is also used in greater quantities for the intentional purple color of amethyst glass. In this state it doesn't glow.
(Crystalclear:)I gave up on my UV light, I think I need a new one. That may be. Fluorescent lights gradually lose their effectiveness, and UV lights are no different. English pieces of cut glass, I have no success in changing color under the light. Interesting. If you know any details about the ones you've tested, I love to hear them, for instance maker, date or period (approximate is fine), how many you've looked at. I forgot to say that
I'm just as interested in knowing about English (and French, and others) cut crystal that doesn't fluoresce as that which does.
(I used the "glow" button to catch attention of those just scanning the thread...cool button!). I did have a Clark piece that the color was a deep yellow and I have not seen any other glass have the same color. Also interesting! You mean TB Clark and Co., the ABP company, right?[/quote]
Thanks for your comments, everyone!!! :hiclp:
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I have had pieces of green and blue non-uranium pressed glass with the manganese glow
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I wonder why they would have used manganese in those cases. Will wonders never cease? (Hope not!)
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Yes krsilber that would be T.B. Clark, it has glowed (if you can use that word) the brightest of any piece I have ever had.
Some interesting notes I just viewed my Libbey bowl under black light, no glow which is no surprise it is from the later period of the flowers.
But where 2 stems meet on the bowl, they glow orange. Its not dirty so can't be that.
Another celery from the flower period is a pale yellow. The Clark I was talking about was a dirty lemon color, bright for ABP.
Take back what I said before, there is a piece I do not know the maker, it is a perfume and the sterling silver marks are Birmingham, this glows a pale green glow. Mark on the silver is around 1911.
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Yes krsilber that would be T.B. Clark, it has glowed (if you can use that word) the brightest of any piece I have ever had.
Some interesting notes I just viewed my Libbey bowl under black light, no glow which is no surprise it is from the later period of the flowers.
But where 2 stems meet on the bowl, they glow orange. Its not dirty so can't be that. Could it be that you are seeing the effects of a very faint overall glow better in that spot? Often it's brighter in cut areas.
Another celery from the flower period is a pale yellow. The Clark I was talking about was a dirty lemon color, bright for ABP. I don't know off hand and don't have time to try to find out, but it's possible Clark imported some of their blanks. That might account for the different color. I'll look into it but it might be a few days before I can get back here.
Take back what I said before, there is a piece I do not know the maker, it is a perfume and the sterling silver marks are Birmingham, this glows a pale green glow. Mark on the silver is around 1911.
Sounds interesting! Do you have any photos of it? Even one with normal light would be nice to see.
The trouble with photos of glass under UV light is that you really can't compare colors accurately, except perhaps among a group of glass in the same photo or at least taken by same the camera. They're too dependent on camera settings and other factors.
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No Kristi
The libbey bowl does not glow anywhere else, just where the 2 stems meet and I mean a bright orange like the fruit. Never noticed that before.
The perfume is running in an auction and I will post the piece as soon as it is finished.
I think I need to learn how to keep my shutter open longer on my camera when I take a picture so that I can capture the colors of the glass under UV light. Have to do some research on that one, because you have to see this orange.
As far a Clark, yes you are right they did import some of their glass.
Now I had a Neola bowl from libbey that was cut and it was pale yellow under black light.
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I have a Boston and Sandwich engraved bowl that glows pale yellow, too.
The Libbey is a curious one. Can you post a picture in normal light? I'd like to see where on the bowl they come together.
I have had pieces of green and blue non-uranium pressed glass with the manganese glow
This is bugging me. Were the colors particularly pure? I can't see why you'd use enough manganese that you'd see a blue item glow green. Is it used for something besides coloring and decoloring?
What kind of pieces were they?
That blue uranium Fenton piece of Mark's is pretty cool.
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The were just relatively low quality bits of pressed glass, probably from pre 1950. I don't have them to hand, I may not even have them any more. I am pretty certain that this is an example (BTW it's not Bagley, it's either Czech or Walther, don't have time to look now) here (http://cgi.ebay.co.uk/ART-DECO-GLOWING-BLUE-BOWL-GORGEOUS_W0QQitemZ110258065557QQihZ001QQcategoryZ64878QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)The glows in the dark is a clue, if you have to be in the dark to see the glow it's manganese
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Is it used for something besides coloring and decoloring?
Yes, it was also used as an oxidising agent to help decompose any organic elements, but not an important one.
As to colour its effects vary with the level of oxidisation and can be used, with other materials, to give Reddish Violet, Bluish Violet, Brownish Violet, Indigo Blue, Reddish Brown, Grey and Black in Soda Glass. For lead glass - Red Violet, Blue Violet and Grey.
Arsenious Oxide was used to reduce the colouring effect of Managanese Dioxide used for decolorising. Black glass is a combination of high levels of Manganese Dioxide and cobalt iron or copper oxide.
As a decloriser it was more effective in Potash Glass than Soda glass, effective with lead glass melted in a pot but not in a tank. The effect of reheating tends to reduce the colour so this reduction had to be taken into effect when preparing the batch.
All of the above are gross simplifications of information in Cousen and Hodken. The reality is that its effects are subject to a huge range of parameters and in 1925 the knowledge was largely sketchy based on observation and experience rather than research.
Nickel Oxide was used for decolourising instead in Germany.
A remarkable material.
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Yes, it was also used as an oxidising agent to help decompose any organic elements, but not an important one.
Could this me simply an extension of its action as a decolorant? Oxidation is the way it neutralizes the coloring effects of iron.
effective with lead glass melted in a pot but not in a tank.
I believe lead glass was usually melted in covered pots. Otherwise reaction with the atmosphere cause the lead to come out of solution and precipitate.
The reality is that its effects are subject to a huge range of parameters
...like so many of the constituents of glass!