From: fish slapping maniac 19/01/2001 23:35:04 Subject: Green Glass post id: 211027 When you look through the 'edge' of a sheet of clear glass, why does it appear to have a green tint? Is clear glass really green? From: Boris ® 19/01/2001 23:36:50 Subject: re: Green Glass post id: 211029 I think the higher iron content the greener the edge of the glass will appear. From: Boris ® 19/01/2001 23:43:00 Subject: re: Green Glass post id: 211033 "As for coloured glass, the commonest colouring agents are iron, manganese, chromium, copper, and cobalt; but iron is the main colouring material which gives glass a greenish tinge. Each of these colourants imparts to glass a characteristic tint, and causes the absorption of radiation at specific wavelengths. The iron content in ordinary glass determines the transmission of solar radiation at different wavelengths. Glass with a low iron content allows high radiation transmittance at all wavelengths of the spectrum. For wavelengths in the near-ultraviolet region (A) the transmittance is up to about 90%. As the iron content increases and the glass attains a darker green colour, the transmittance in the near-ultraviolet region (A) decreases, hut remains at a fairly high level in the visible region (400 to 700 nm)." http://almashriq.hiof.no/lebanon/600/610/614/solar-water/unesco/29-34.html From: Dr. Ed G (Avatar) 20/01/2001 0:20:44 Subject: re: Green Glass post id: 211059 Yup Boris is completely correct. In general, normal float glass used for windows and the like has a natural iron content which causes an attenuation in the transmission of light at the blue end of the spectrum which gives it a greenish appearance when a pane is viewed end on (because the light has to pass through more of the glass). I regularly used to do consulting for Pilkington Glass who wanted the light transmission of their "low-iron" glass measured. The made low iron glass simply by sourcing sand with a particularly low iron content and removing as much iron as possible by filtering the sand through magnets (though, the greatest reduction is achieved by using the right sand in the first place). Other impurities will also affect the colour or transmitted light, but iron is the most significant. Soupie twist, Ed G. From: Boris ® 20/01/2001 0:23:35 Subject: re: Green Glass post id: 211062 Thanks for that Dr Ed :-) "Glass is a substance in a condition which is continuous with, and analogous to, the liquid state of that substance, but which, as a result of cooling, has attained a viscosity so great that it is for all practical purposes rigid. The American Society of Testing Materials defines glass as "an inorganic product of fusion which has been cooled to a rigid condition without crystallizing". Thus, glass is a supercooled liquid. Its structure has short-term, but no longterm order as in crystalline materials. Ice is an example of a glass with a noncrystalline solid structure." http://www.evanite.com/html/glass4.html From: Alan™ ® 20/01/2001 8:28:59 Subject: re: Green Glass post id: 211131 Unfortunately in the second posting Boris, your incorrect, glass is definitely a solid. All solids if you wanted to could be called supercooled liquids, they all flow extremely slightly under a process called creep, which is really a difusion process. This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.