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Comments

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  Stefany Tomalin October 22, 2011 at 4:17pm

  held up against the sun- shows the greeny glow- sorry about the focus- all done with only one free hand...
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  Edith D October 22, 2011 at 8:07pm

  Stefany...I never heard the term dichroic (a duel variation in adsorption of light wavelengths) applied to beads, but it is obvious from your photo that these have some unique optical properties.  Fascinating!  Do you know what compound is causing this phenomenon?  These beads must be very interesting under a polarizing microscope!
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  Kathleen McCabe-Elsey October 24, 2011 at 3:05am

  Hi Edith,  Lampworkes use Dichoric in glass beadmaking also. Here are some from some USA artists, Paule radke and Tom Holand. 

   Dichroic glass is glass containing multiple micro-layers of metals or oxides which give the glass dichroic optical properties. The main characteristic of dichroic glass is that it has a particular transmitted color and a completely different reflected color, as certain wavelengths of light either pass through or are reflected. This causes an array of color to be displayed. The colors shift depending on the angle of view. Dichroic glass is an example of thin-film optics.
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  Stefany Tomalin October 24, 2011 at 7:01am

  my understanding of the true meaning of the term "di-chroic" glass is that it displays 2 colours, one with reflected light, the other with transmitted light.

  Swarovski's 1950s "Aurora Borealis" faceted beads have dichroic properties but its only on the surfaces of the facets, its not the glass.

  however the term then got adopted to describe newly-invented glass with gorgeous lustrous coatings of metallic oxides which were, i believe first marketed in the 1980s by "Bullseye" -a US glass manufacturer who supplied to glass crafts artists. i met Cay Dickey at that time, one of the very first to use the glass for her lampwork beadmaking.

  the antique blue beads i show are dichroic rather than lustrous but its a quality of the glass itself, not the effect of a coating layer.
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  Edith D October 24, 2011 at 7:47am

  Thanks all for this really interesting information!  I took a class in optical mineralogy as part of my studies years ago, so I am very intrigued by this.  Since I never looked at beads, this is something new for me...I love finding out about how things are made, but I am sure this information is also useful for both identifying and dating certain types of beads.  Thanks again!
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  Stefany Tomalin October 24, 2011 at 7:51am

  Kathleen

  thank you for showing the examples of recent artist-made lampwork beads with the lustrous "dichroic" effect-
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  Kathleen McCabe-Elsey October 24, 2011 at 3:57pm

  Hi Edith,  Here is an article on NASA's dichroic glass and a story of it's use

  http://ezinearticles.com/?Dichroic-Glass---A-Product-of-NASA-Now-Ob...

  and another:

  http://pbmo.wordpress.com/2011/04/13/dichroic-glass/

   

  Dichroic:  -- the property of showing different colors when viewed in different directions -- as the light dances on the glass surface it changes color.  Developed by NASA, dichroic glass has
  microscopic, thin layers of rare oxides vacuum sprayed on the glass, altering the refraction index of the spectrum, causing the light rays to bend in
  wonderful color play.
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  Kathleen McCabe-Elsey October 24, 2011 at 4:06pm

  

  Another cool example...:)
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  Edith D October 26, 2011 at 11:04am

  Thanks for this Kathleen...very intriguing!
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  Stefany Tomalin October 26, 2011 at 11:19am

  now there's a fellow who definitely drank too much...