Author Topic: Sklo Neodymium Paperweight on eBay  (Read 2330 times)

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Offline flying free

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Re: Sklo Neodymium Paperweight on eBay
« Reply #20 on: January 17, 2011, 03:10:51 PM »
wow!  and thanks  :hiclp:  that is a great explanation.  
Actually a few of my glass pieces look weird under fluorescent light, it definitely changes the appearance - I prefer good old fashioned lightbulbs, but I know their days are numbered.
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Offline misha

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Re: Sklo Neodymium Paperweight on eBay
« Reply #21 on: January 17, 2011, 04:37:22 PM »
No worries.... the confusion caused by the term 'energy saver' is a bit dubious especially when a bright Halogen, short life, heat generating, energy wasting lamp is sold as such. Rather annoying actually. These are good for displaying glass and jewellery because of the intense white light they produce. Thats about all they are good for!
 
Here is an image of a very low quality rubbish type lamp that failed after less than 10hours use. It is dimmed down so I could take the photo. You can see the inner bulb and outer that fell on my lounge... lucky I wasn't sitting there at the time. The metal wires supporting the inner bulb are at 240V This is an electric shock and UV output hazard like so.

http://i756.photobucket.com/albums/xx203/reproducer/Halogenpieceofcrap.jpg

I don't have a problem with CFL because I buy the high wattage 'cool white' type that actually have a higher lumen output than those good [subjective] old filament lamps now outlawed here in Australia.

Another type of lamp I didn't mention there was the Discharge Lamps you see used for high powered street lighting, factories and shopping centres. These are of a similar nature to a fluorescent lamp and vary in types of gas used. Their efficiency [lumen/watt] varies accordingly.  I uses a 150W Metal Halide type to light up a 1/4acre car parking area here. The light output is incredible... far higher than what a fluro or incandescent could ever give for that wattage.
Anyhow,  I suspect the light spectrum output of these types of lamp would also produce that colour change in neodymium glass, depending on the type... being  Mercury Vapour [blue bias], High Pressure Sodium [yellow bias] and Metal Halide [blue bias].

I'm like to know exactly what light spectrum triggers this colour change in neodymium glass, an interesting affect to me. From that I may be able to advise the optimum lamp to use.

The other type of glass of interest to me is the diachronic glass.  I have several pieces that use this reflective/filter glass I find very pretty. Fascinating stuff.   


Offline misha

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Re: Sklo Neodymium Paperweight on eBay
« Reply #22 on: January 18, 2011, 05:31:40 PM »
More info on Neodymium Glass

http://en.wikipedia.org/wiki/Neodymium

Neodymium glass (Nd:glass) is produced by the inclusion of neodymium oxide (Nd2O3) in the glass melt. Usually in daylight or incandescent light neodymium glass appears lavender, but it appears pale blue under fluorescent lighting. Neodymium may be used to color glass in delicate shades ranging from pure violet through wine-red and warm gray.

The first commercial use of purified neodymium was in glass coloration, starting with experiments by Leo Moser in November 1927. The resulting "Alexandrite" glass remains a signature color of the Moser glassworks to this day. Neodymium glass was widely emulated in the early 1930s by American glasshouses, most notably Heisey, Fostoria ("wisteria"), Cambridge ("heatherbloom"), and Steuben ("wisteria"), and elsewhere (e.g. Lalique, in France, or Murano). Tiffin's "twilight" remained in production from about 1950 to 1980.[13] Current sources include glassmakers in the Czech Republic, the United States, and China.

The sharp absorption bands of neodymium cause the glass color to change under different lighting conditions, being reddish-purple under daylight or yellow incandescent light, but blue under white fluorescent lighting, or greenish under trichromatic lighting. This color-change phenomenon is highly prized by collectors. In combination with gold or selenium, beautiful red colors result. Since neodymium coloration depends upon "forbidden" f-f transitions deep within the atom, there is relatively little influence on the color from the chemical environment, so the color is impervious to the thermal history of the glass. However, for the best color, iron-containing impurities need to be minimized in the silica used to make the glass. The same forbidden nature of the f-f transitions makes rare-earth colorants less intense than those provided by most d-transition elements, so more has to be used in a glass to achieve the desired color intensity. The original Moser recipe used about 5% of neodymium oxide in the glass melt, a sufficient quantity such that Moser referred to these as being "rare earth doped" glasses. Being a strong base, that level of neodymium would have affected the melting properties of the glass, and the lime content of the glass might have had to be adjusted accordingly.[14]

Neodymium compounds were first commercially used as a glass dye in 1927 and they remain a popular additive in glass. The color, due to the Nd(III) ion, is often a reddish-purple but changes with the type of lighting, due to fluorescent effects.

The evolving technology, and improved purity of commercially available neodymium oxide, was reflected in the appearance of neodymium glass that resides in collections today. Early neodymium glasses made in the 1930s have a more reddish or orange tinge than modern versions which are more cleanly purple, due to the difficulties in removing the last traces of praseodymium in the era when fractional crystallization technology had to be relied on.

[13] "Chameleon Glass Changes Color". http://coloradosprings.yourhub.com/CrippleCreekTellerCounty/Stories/Arts/Story~443258.aspx. Retrieved 2009-06-06. [dead link]
[14]  Charles Bray (2001). Dictionary of glass: materials and techniques. University of Pennsylvania Press. p. 102. ISBN 081223619X. http://books.google.com/?id=KbZkxDyeG18C&pg=PA102.


 

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