Glass Message Board
Glass Identification - Post here for all ID requests => Glass => Topic started by: Leni on April 17, 2007, 01:49:49 PM
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I have just had to clean some of my paperweights because I noticed some of them were looking 'cloudy', and I found when I opened the cabinet that they were in fact not just dusty as I had supposed, but were covered with a sort of film! I also noticed an unpleasant smell (which also got on my hands as I cleaned the weights, and is proving quite difficult to remove >:()
I remembered the subject of 'oily glass' being discussed here previously, and I found this thread in the Archives: http://www.glassmessages.com/index.php/topic,395.msg1934.html#msg1934
What was interesting was the fact that it was only the Chinese weights which were affected! As well as all my 'dime-a-dozen' Chinese, I have in the cabinet a couple of Caithness flower weights, a Mtarfa, a Murano and a couple of Bohemian - none of these were cloudy at all!
And the horrible thing is, the surface of the Chinese weights is actually beginning to show damage in a couple of cases! There appear to be circular marks like the 'bruises' sometimes seen on paperweights which have been knocked or dropped, yet I know these weights have not been damaged in the time I have owned them, and definitely showed no such marks when I first bought them!
I was particularly interested to read the post in the previous thread on oily glass where Frank gave a reference to a site which talks about the conservation of glass and the causes and effects such damage can have, and it would appear some of these weights are actually suffering a degree of devitrification. I suspect this is as a result of being kept in a closed, albeit not completely airtight, cabinet.
http://glassgallery.yobunny.org.uk/albums/userpics/10048/dime-a-dozen_cabinet.jpg
I was interested in the final comment in the thread, where Gareth says he found that proximity to Oak was a factor. However since my cabinet is a fairly cheap modern (Chinese, again! ::) ) product, I think it more likely that humidity is to blame. I say this because I have other Chinese paperweights, particularly the ones on the top of the cabinet, which have not shown this problem.
I am posting this here rather than in the paperweight forum, because I feel it is a glass issue specifically, as it could obviously affect any Chinese (or other cheap, soda-based) glass!
You have been warned! :(
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Oh dear. That will certainly sort out a few collections in time. Could you recognise the smell, did you try tasting?
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Could you recognise the smell, did you try tasting?
Youngest son licked one. He said it tasted slightly salty, and bitter. He also described the smell as "Horsesh*t" :-[ ::)
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The smell is vinegar, the taste is salt & the surface is sticky - it must be Chinese, Romanian or Crackle glass!
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For me the smell is between vinegar and ammonia, surface sticky (haven't tried licking it yet !).
I've got two tall Nyman vases side by side, both geniune, and only one is oily - the one right next to the side of the old oak cabinet (which is an original fitted cabinet approx 100 years old). The one next to it (say 9 inches from the side of the cabinet) - no grease.
And thankfully no apparent damage to the glass.
As the cabint is on an outside wall, I can only surmise that the cold glass is causing something to condense on to it, but why only one vase is affected, the other shelves are fine - a complete mystery.
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At the risk of being thought pedantic, may we please be careful with the use of the word "devitrification"? This is the effect which can occur if glass is held at a high temperature (normally still in the furnace - much higher than annealing temps) for too long and crystals of various compounds start to form. Crystals are of course not glass (hence devitrification or "de-glassing" to coin a word!). This can be a serious defect if the crystals reach the finished article as they have totally different properties to the parent glass and therefore can set up huge stresses which are impossible to anneal out. "Devit" for short in the trade. Importantly in the context of this thread, I know of no mechanism whereby devit can form at room temperatures - any crystals seen may be forming on the surface from whatever is leaching out of the poor quality glass.
Incidentally, CONTROLLED devitrification is how glass-ceramics are made.
Adam D.
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Ah !!!
Is this the answer ??
http://www.rsc.org/chemistryworld/News/2005/September/26090501.asp
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Wow! That looks like it is the answer! So 'Oak' is a bit of a Red Herring perhaps? It seems as if any wooden cabinet is a possible risk, if the humidity / temperature etc. are right (or should I say wrong :( )
As far as the smell goes, I wondered if there was possibly a combination of the smell of the chemicals coming off the glass combining with the varnished finish of the cabinet. That's what it smelled like to me (whatever son may have thought ::))
Adam; apologies if I used the word devitrification wrongly. I picked it from the article in Frank's link on conservation of glass, possibly without sufficient care as to its meaning :-[
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Leni, I have two Gentile paperweights that "sweat" if they are put in the curio cabinet. None of my other weights, including the Chinese ones do that. If I leave the Gentile ones out of the cabinet and just sitting in air, they are fine.
Terry
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http://www.rsc.org/chemistryworld/News/2005/September/26090501.asp
The article refers among other things to Formaldehyde, which is a constituent of most but not all MDF. If not properly primed, MDF can leach formaldehyde, so perhaps this problem could occur with MDF furniture as well as timber.
Doesn't sound as if licking affected glass is particularly advisable. :P ::)
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Hi all,
I found this topic interesting and scary. Having noticed a 'wet' feeling to some of my glass at times. I gather this is the same oily feeling being referred to. So essentially Im damaging my glass...but what to do?
My glass is in 2 big wood and glass cabinets...sitting on wooden shelves..
Is there a preventative for this happening...? Besides switching cabinets which I cant afford?
Selina
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As moisture seems to be a prerequisite, you could try one of those moisture traps in the cabinet - only a guess though.
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It is a vicious circle, keeping the glass in a cabinet keeps it clean and safe but at risk of decay - keep it in open air and it gets dirty and is at greater risk of accidental damage.
In general this does not seem to be a destructive problem in the short term. A dry atmosphere is helpful but very difficult to achieve for most people, all glass cabinets may seem to be a solution, but what about the polutants released from the silica used to join the pieces. My own glass cabinets are a shop display cube system in which panels of glass clip together without glue. It has the advantage of free air flow and unlimited builkding combinations... downside, the dust gets in as easily as in the open!
Also some of the reactions desribed in the various references have a time factor, so not too irregular cleanings will tend to prevent the chemical reactions that cause additional damage.
When mentioning pieces of glass with these problems, please indicate colour and origin if known - it might lead to a deeper understanding.
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problems, please indicate colour and origin if known -
Orange glass is particularly vulnerable, I noticed.
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We all try to figure out what we are doing wrong when our glass "sweats.'
IT'S NOT OUR FAULT.
It's caused by the glass manufacturers putting too much soda ash in the glass. For them, this allows the glass to be worked longer and cooler, (costs less for fuel, costs less for imperfect work). For us it means that eventually our prized pieces will no longer be pristine.
There doesn't seem to be any way to keep this from happening, a friend of mine had a very special Gentile weight that separated horizontally after years of 'perspiring.'
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IT'S NOT OUR FAULT.
Except, of course, we can contribute by not taking care of glas that requires an external catalyst to promote the problem. But we are covering two different causes in this case and we can't always blame the glassmaker for lack of knowledge on the technology and in some cases lack of the technology.
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Other than a new cabinet I see moisture traps were mentioned as a possible cure .
The packets of crystals used to package with cameras for example would be ideal for this , if you have a few of them to swap over they can be dried with heat and reused , I'd imagine that these would be easy enough to conceal below shelves with tape for example .
Just a thought in what is a fascinating yet scary topic !
Dave.
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Hi Dave et al.
Armin and me are back - this is my first post.
silicagel - Dave?
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Welcome back Pamela! We missed you! (Does that translate well?)