Talk:Fused quartz

message: I don't understand the difference between this and glass.  Aren't both non-crystalline silicon dioxide? - Omegatron 17:57, Jun 13, 2005 (UTC)
:Glass is about 70% silica, Fused quartz is much more pure. See the section on Glass Ingredients. -dmmaus 03:09, 13 December 2005 (UTC)
replies: text: To be clear, fused quartz is a type of glass. It's just glass with higher silica content than normal (ideally 100%).--Srleffler 15:31, 19 April 2006 (UTC)
thread_title: Untitled

message: Comment about optical properties:
The Sellmeier equation coefficients taken from Malitson (1965 - Interspecimen  Comparison of the  Refractive Index of Fused  Silica) are measured and intended for 20°C. These values where determined at 20°C and 30°C only and in section "V. Thermal coefficients of index" it is clarified that a simple relation for various temperatures over this massive wavelength range for a precise calculation of the refractive index is not valid.
As a reference for the temperature dependence refractive index the following paper can be used:
"The temperature dependence of the refractive indices of fused silica and crystal quartz 
T Toyoda and M Yabe 1983 J. Phys. D: Appl. Phys. 16 L97 doi: 10.1088/0022-3727/16/5/002)"
However, it was only possible to cover a range from 0.45 to 1.6 micron and 20°C to 400°C.
Therefore, I would like to take the 0 to 700°C of the page.
I already added the information that the values presented are valid only for 20°C!
ToLam (talk) 15:56, 30 May 2010 (UTC)
thread_title:  Optical properties 

message: The statements about quartzite are problematic. The high temperatures required for fusion of quartz do no occur in the crust of the Earth except when meteoritic impacts are involved. Most quartzites are the result of slow solution/precipitation events in aqua, not fusion. Captainbeefart (talk) 15:37, 28 May 2011 (UTC)
thread_title: QUARTZITE 

message: That's not fused quartz, it's a cheap polymer resin (used on later EPROMs).  The ones with a glass window have this added externally to the case, as a coverslip. Andy Dingley (talk) 10:56, 14 May 2013 (UTC)
thread_title:  EPROM windows 

message: https://en.wikipedia.org/wiki/Fused_quartz#cite_ref-7 -> http://www.sciner.com/Opticsland/FS.htm - This domaine is up for sale (2015-02-02). I suggest deletion of the reference. 131.130.142.98 (talk) 12:11, 2 February 2015 (UTC)
replies: text: I updated the page to point to the Internet Archive. WikiWisePowder (talk) 17:35, 27 February 2016 (UTC)
thread_title: References

message: I removed the following sentences:
:To eliminate these by-products, new processes have been developed using an alternative feedstock, which has also resulted in a higher purity fused silica with further improved deep ultraviolet transmission.
It has been tagged as unsourced since 2014 and is very vague and possibly promotional. WikiWisePowder (talk) 17:25, 27 February 2016 (UTC)
thread_title:  Unsourced statement 

message: Thanks to Plantsurfer for reverting the recent addition, which said fused quartz was produced in China thousands of years ago. I was going to revert myself, but took a moment to check my books to be sure. 
The problem with this theory is that the glass-melting temp (Tm) of quartz is ~3000 degree F, which is higher than the melting point of iron or steel. The ancients could not produce temperatures high enough to do this. Quartz has other problems as well. It has a very narrow glass-working range, meaning it goes from a thick, viscous liquid to a runny, free-flowing liquid very fast if overheated (whereas impurities in other glasses lowers the melting temp and broadens the working range). Within the working range, it is very thick and sluggish, making it very difficult to work, blow, or weld. It tends to absorb water when heated, especially with common hydrocarbons, which causes clouding of the glass (translucency instead of transparency). To avoid this, an oxyhydrogen flame must be used. It has very high (almost metal-like) thermal conductivity compared to other glasses, meaning you can't just heat the ends to weld it; you must heat the whole thing. Quartz also begins to vaporize just below the melting temp, which forms microscopic bubbles in the glass, also causing clouding. Not to mention, it's bright! When heated to a white-hot temp, it is far brighter than steel because the light is more like greybody radiation than blackbody, meaning that the glass is not opaque to its own light. (You need a full-on welding helmet with a shade 10 filter to avoid burning your eyes and face.) 
The quartz used in making ancient glass contained many impurities, of which iron was the most prevalent. This is the reason ancient glass was almost always tinted dark green or brown (like a beer or wine bottle). These impurities lower the melting point, but made it very hard to obtain a clear glass. (In fact, the ancients were far more skilled in making colored glass than clear). Clear glass didn't exist until the Venetians invented "crystallo" glass (soda-lime), which was more-or-less covering the impurities with more impurities. The photos added were definitely not quartz, and the rose-colored impurities are proof of that. 
Fused quartz was first made in England. The first person to fuse crystal quartz was Gaudin in 1839. He was able to make small strands of it, but that was all. He did, however, make note of its curious mechanical properties, in particular its mechanical strength and extremely low coefficient of thermal expansion compared to other glasses. Quartz was necessary for making high-pressure arcs, particularly out of mercury. Shenstone was the first to make small tubes or bulbs out of it in 1900. In 1904, Heraeus displayed the first mercury-arc lamp in Paris. Quartz manufacturing developed rapidly after that, hand in hand with arc lighting, mainly due to companies like GE, Westinghouse, or Sylvania. The first telescope mirror was made in 1931 by GE, but the difficulties in manufacturing it in large sizes didn't get worked out until the 1950s. For more info, see: Electrical Review, Volume 64 by George Worthington. Zaereth (talk) 18:30, 16 April 2018 (UTC)
thread_title:  Quartz glass history