Glass Message Board
Glass Identification - Post here for all ID requests => Glass => Topic started by: krsilber on May 08, 2008, 08:31:49 PM
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I got a matching pair of Harrach 10 1/5" pitchers yesterday. The inside is pink. Over that is a layer of opaque white. Then I believe there's a thin layer of dense, fairly translucent yellow, and on top of that, colorless. Either that or the top layer is actually yellow, but I don't think so.
Last night I turned the UV light on it, not expecting much - the yellow doesn't really have the tone of uranium. But wow, did it glow! Not green - ORANGE! Bright orange. I'd noticed in the past a tendency for colorless Bohemian glass to glow a dull, dirty orange, but nothing like this. And the pattern of the the glow was also interesting: part of the neck up to the rim glows brightly, and about the bottom 1/3 of the body is also bright, but not quite as strong. The rest seems to have a faint greenish color. And there's one spot on the bottom where the pontil has been ground to the white that glows purple (and it's not just a reflection of the UV bulb), so it's got to be one of the upper layers that's glowing orange. There's no obvious difference in the glass between what's orange and what's not.
Has anyone else seen a bright orange glow like this, and on what?
Photos: Some are in my gallery, some not. Here's the whole pitcher in normal light:
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9961
Here's the bottom of it:
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9960
And one of the inside. The pink appears to be throughout the interior, though it's a bit hard to tell.
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-9962
Below is a photo of the pitcher in UV, then a couple with a uranium custard glass cased basket for comparison, one in UV and one in normal light, just so you know my bulb isn't funky! (I would like info about the basket, if anyone knows anything about it.) In the UV photo there's also a Heisey jar that's got a nice manganese glow to it, but it's overwhelmed by the glow of the other pieces. You can sort of see the spot in the middle of the bottom of the pitcher that is purple, though you can't really tell how purple it is.
The other matching pitcher has pretty much the same pattern, though the glow on the neck extends further down.
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Cadmium sulphide http://www.glassmessages.com/index.php/topic,95.0.html :) (Thanks to Glen for the earlier info. ) My amberina goblet glows orange at the base (the yellow part) too.
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Thanks, Anne! It had actually crossed my mind that it might be cadmium. It must glow only with specific valences, as Tom said (I know that Tom!), otherwise there's be a lot more glowing orange stuff out there. Unfortunately, Glen's article link doesn't work anymore, and your photos are all gone. Maybe Glen will see this and provide another link to her article...and I'd love to see your amberina goblet!
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Psst Kristi, Glen's a gal! ;) Goblet pic to follow. :)
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Oops, thanks for the correction! I edited my post to reflect that.
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In the 19th century the structure of the Bohemian glass industry, separation of blowing and decorating led to a distinct difference in the glass composition, Commissioner Blake reported in 1878 that the typical composition of Bohemian White glass was:
Pulverised quartz (Plentiful compared to sand) 100 parts
Carbonate of Potash 28-32 parts
Slacked lime 13-15 parts
Oxide of Manganese 1 part
Arsenic 3 parts.
This white glass was harder then American flint glass. Such variations are likely to result in different fluorescence then found elsewhere. Carbonates tend to fluoresce in the yellow region, Quartz is variable depending on source, Lime is again a yellow fluorescent, while Manganese gives pink which combined presumably (speculation) looks pinkish orange.
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I just sold this Franz Welz piece on eBay - very similar glow: :chky:
Congrats on the Harrach pair, Kristi - I was asleep on that one. :hiclp: :mrgreen: :hiclp:
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That's a mighty pretty piece, Warren! Nice glow, too!
In the 19th century the structure of the Bohemian glass industry, separation of blowing and decorating led to a distinct difference in the glass composition, Commissioner Blake reported in 1878 that the typical composition of Bohemian White glass was:
Pulverised quartz (Plentiful compared to sand) 100 parts
Carbonate of Potash 28-32 parts
Slacked lime 13-15 parts
Oxide of Manganese 1 part
Arsenic 3 parts.
This white glass was harder then American flint glass. Such variations are likely to result in different fluorescence then found elsewhere. Carbonates tend to fluoresce in the yellow region, Quartz is variable depending on source, Lime is again a yellow fluorescent, while Manganese gives pink which combined presumably (speculation) looks pinkish orange.
There's that ambiguous "flint" word! I was just reading a flint thread from the archives. Do you mean American lead glass?
Are you basing these glow colors on how they appear in glass, or on raw minerals?
Manganese in American glass fluoresces greenish. It's actually an activator in its mineral state and fluoresces differently depending on what it's found with.
While some lime fluoresces yellow in its natural state, it can also fluoresce other colors depending on "contaminants." Lime glass doesn't necessarily fluoresce at all.
I didn't know that about the quartz. That's interesting. I imagine minerals found in the quartz could affect its glow color. That would explain the relatively wide variation in colors I've seen my colorless Bohemian glass fluoresce.
Baldwin in Moser Artistry in Glass compares the way Bohemian "crystal" (leadless), Venetian crystal (ditto) and European lead crystal glow in shortwave and longwave UV light. Apparently using the combination he's able to differentiate among the three. He also gives a formula for Bohemian crystal similar to the one you posted but with soda (NaCO3) as well.
I'm fascinated by the variation in the way glass glows in UV. It's something of a controversy in the US whether it actually means anything, or whether it's useful in attribution. I think it can be useful as a tool as long as one is careful about the conclusions one draws from it, and is knowledgeable about it. Glass chemistry is so complex that making inferences about what it contains based on glow color under longwave UV alone is really hard. Manganese, for instance, will only glow in a certain valency state, which is why amethyst glass doesn't glow. In colorless glass it oxidizes (or reduces, I always forget) iron, and in doing so becomes UV reactive.
I suspect the valency state of cadmium is heat-dependent, and that is why only parts of my pitchers glow bright orange (and only the amber part of Anne's goblet).
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... It's something of a controversy in the US whether it actually means anything, or whether it's useful in attribution. I think it can be useful as a tool as long as one is careful about the conclusions one draws from it ...
I agree that UV analysis is a good tool when used with care and understanding. And I believe that UV results cannot be used for basic attributrions - unless, of course, we know the UV reactions for every piece glass made by every maker over all time since glass was first utilised. If we had all that data, we may then find that a particular maker's items do show a truly unique UV reaction and therefore that result could be used in an attribution.
But on the basis of use as a tool to assist in other observations, UV can show definitive results. For instance, by using both longwave and shortwave I was able to show that Ysart paperweights could be sorted into distinct periods. By that means, the three main periods of Paul Ysart's output can be identified, as can the two periods of "Early Vasart" and "Later Vasart". That seems to be pretty much the same sort of 'dual UV analysis result' as Kristi has mentioned for "Baldwin in Moser Artistry in Glass". However, for the Ysart weights, it is still not possible to use those UV results to separate Paul Ysart items of the 1930s-1950s from "Early Vasart" work - as they fluoresce in the same basic colours under the respetive wavelenghts.
On the general subject of orange fluorescence, I am fairly sure that there is an interesting orange glow at the edges of the cut areas (!) in my couple of "Egermann style" ruby-flashed items. I must check that out some time.
Edited to add:
Sorry - I was wrong - it's not an orange glow on the cut pieces. It's actually a bright, pale yellow! And that's under shorwtave UV. For longwave, much of the cut parts, not just the edges, shows as a weak orangy-yellowy-greeny colour (depending on how long I stare at it).
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I was just reading an old thread on UV here http://www.glassmessages.com/index.php/topic,1263.0.html and noticed you were interested in it, Kevin. I've been thinking about starting a thread on it myself, but don't know if it's already been talked to death around here. I was interested in whether rich cut glass made over there glows, and what color.
I have a theory about your cut areas glowing. Hmm, no two alternate theories. One is that the outside of the stain got hotter than the inside, resulting in different valences of selenium. But that seems unlikely. How about the stain nearest the glass fused with it, resulting in a chemical change that causes glowing.
This is stained, right? Wait, you said flashed. Can you post a photo?
I have a Bohemian cut and engraved piece with an amber stain that glows bright orange in LWUV.
I'm so glad to hear you say "Egermann-style"! Americans don't seem to understand that others besides Egermann made/make the stuff.
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Kristi - the article (updated link below) was about vaseline, and in it the question was posed; "what causes an orange glow?" I spoke to John Boyd (at Boyd Art Glass) and he gave me the following answer (which is also in the article).
"there are several metal oxides that fluoresce. The only one that comes to mind that will flouresce orange in glass is Cadmium Sulfide. It is the only colorant that will make glass yellow. Actually, cadmium is one of the colorants that "needs" a reducing flame. But to help it to the brown side (topaz) I think I would add a pinch of blue, black Copper Oxide." (thanks to John Boyd for the info).
http://www.carnivalglass.org/newbies/10.asp for the updated link.
And to Anne.....thank you ;) (especially for pointing out my gender :-* :-* ;D)
Glen
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Thanks, Glen! So looks like cadmium sulphide is the culprit. I wonder if he meant it's the only fluorescent colorant that's used for yellow (but even that's not true, since there's uranium), since there are yellow glasses that don't contain it.
Still a bit of a mystery what created the pattern of glowing in mine. Suggests that not all cadmium sulphide-containing glass will glow. Boyd's comment that it needs a reducing flame just confuses things more because it suggests that for yellow it needs to be of a certain valency, and my hypothesis was that on the pitchers it's not all of the same valency. Hmmm.
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Kristi, what is the pattern of glowing on your pitcher? If it had cadmium sulphide of a different valence, what would have caused that? Different batch?
Speaking of glowing orange glass, has anyone looked at Davidson orange cloud under blacklight? The clouds glow the most magnificent orange. Does anyone know the composition? (Is it in Chris' book?)
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You can sort of see the pattern in the top photo in my first post. The brightest orange is at the top, from the spout to about 2" (~5 cm) down the neck. The bottom also glows brightly, but fades gradually above an inch or two from the bottom. The second one is basically the same, but the orange areas are larger. ...Just took a photo of the two together, so you can see. Also another photo of the first, where you can sort of see the green tint that shows up between the orange parts.
My guess is that the change is heat-related. I don't know, maybe it's not a valence thing, maybe it's that a new compound is formed. Perhaps in those areas the layers not only fused, but mixed? I wish I knew more chemistry. But at any rate I can't figure out any mechanism besides heat that would cause the pattern they have.
How about this scenario? Parison blown into mold, removed, reheated so that the punty can be applied, neck is reheated for shaping...you've got struck UV reactive colors.
The Davidson thing sounds cool! You guys talk about these makers, Davidson and Sowerby and others, and I am absolutely clueless. There's a lot of British glass that apparently never hit our shores...or I'm simply clueless.
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I see what you mean - it is strange, isn't it. Can you see any corresponding colour difference under normal light? If that's the mechanism, presumably it was 'struck'* when the pitcher was reheated to form the lip at the top? :huh:
More research into CdS needed! Fenton apparently used cadmium sulphide and selenium in their amberina (under Amberina here (http://reviews.ebay.com/GLASS-GLOSSARY-A-L-Words-Used-to-Describe-Glass_W0QQugidZ10000000004217576). I'm a complete dunce on chemistry, so someone else might have to help! I've just read the Wikipaedia entry on valencies and it pretty much went straight over my head. :chky:
*(Just to define this for anyone reading in the future, as far as I understand it, when a glass vessel has sections reheated to force a chemical reaction which changes the colour, the colour is said to have been 'struck'. Clarification/correction welcomed as always :) )
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I've written here a couple of times about amberina / red and the weird glow it has. Summit's Geraldine's Delight (opaque-ish orangey/yellow/red) is another colour that has that odd orange glow. Here's something I wrote a couple of years back.
'Vaseline' or Uranium - or what?
« Reply #5 on: August 17, 2005, 09:20:36 PM »
Some glass may have an orange glow under UV light. The main coloring agent that causes this is cadmium, usually in the form of cadmium sulphide. The fluorescence can vary from a citron yellow through to a dark red. Cadmium was often added to the batch along with selenium to create red glass. You may note how the amberina sections of amberina/red glass glow. Why? Red glass is re-heated to strike the color—until the moment of striking the selenium/cadmium red glass will react with UV light and glow. But as soon as the red color appears, the fluorescence vanishes.
Glen
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"Can you see any corresponding colour difference under normal light? If that's the mechanism, presumably it was 'struck'* when the pitcher was reheated to form the lip at the top?"
No, I can't discern any obvious difference under normal light. The tone and depth of the yellow seems uniform. The bottom may be just slightly paler, but the difference doesn't conform to the pattern of UV reactivity. And, yes, that was my hypothesis about it being struck (incidentally) at the top to form the upper neck and lip.
...But now, after reading Glen's post, that wouldn't seem to make sense, if in striking a piece for amberina the effect disappears. But then again, things are complicated by the presence of selenium (and whatever else is in there!). I was surprised to see that a modern company like Summit used cadmium, since it's known to be extrememly toxic.
Glass color chemistry "strikes" me as quite complex...and fascinating. If it were simply a matter of a bunch of ingredients thrown together and interacting, it would be one thing, but everything is changed by the addition of heat, whether the atmosphere is reducing or oxidizing, the impurities in the materials, etc.
A year or two ago I was trying to figure out the concensus these days on whether glass is a liquid or solid (it's an amorphous solid, though even that is still debated). I remember reading that even now the chemistry/structure of glass isn't very well understood.
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Stumbled across a possibly contradictory statement about the cadmium sulphide hypothesis. According to this site (David E.'s?), cadmium sulphide fluoresces yellow and selenium fluoresces orange. I'm not sure how it fits into the whole picture, but wanted to add it to the thread in the interest thoroughness.
http://www.glassyeye.com/glasstopics/dichroic.html
Also from the Glassyeye site: "Selenium was originally used as a decolourant to remove the green tinge caused by the natural iron oxides found in glass." This is very interesting to me. I've noticed that a lot of Bohemian colorless glass has a dirty orangish cast under UV, and wondered what it was - maybe it's selenium! I'm probably seeing the same thing Kevin sees in his cut Bohemian glass.