[neilep (OP)]

Hi all,

My name is neil.

Pyrex !!...(it's a brand name yes ?...like Hoover is to vacuum cleaners etc ?)..so..what's the real name of pyrex glass and what make's it so well hard that me would not want to meet an angry Pyrex jug in an alley way !!....can it be used to make thin things like spectacles and glasses ?

[Karen W.]

Hello Neil,

Nice to meet you Stranger! LOL

 That's a good question..!


http://en.wikipedia.org/wiki/Pyrex
I did not see anything about eye glass lens, but indeed a flashlight lens, due to its ability to reflect "higher amounts of light transmittence when compared to plastic lens"..or something like that!

[neilep (OP)]

Thansk Karen,

Wow..it's well over a hundred years old and mentioned in this article:

Borosilicate glass


Borosilicate glass is a particular type of glass, better known under the brand names Pyrex, Kimax, and Endural. It was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works introduced Pyrex in 1915, it became a synonym for borosilicate glass in the English-speaking world. Holophane manufactures original equipment lenses for street lights under the Endural brand name. Bomex is a brand of borosilicate glassware made in China for VEE GEE Scientific, Inc.

In addition to the quartz, sodium carbonate, and calcium carbonate traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass. Typically, the resulting glass composition is about 70% silica, 10% boric oxide, 8% sodium oxide, 8% potassium oxide, and 1% calcium oxide. Though somewhat more difficult to make than traditional glass (Corning conducted a major revamp of their operations to make it), it is economical to produce because its superior durability, chemical and heat resistance finds excellent use in chemical laboratory equipment, cookware, lighting, and in certain cases, windows.

Borosilicate glass has a very low thermal expansion coefficient, making it a popular material for objects like telescope mirrors, where it is essential to have very little deviation in shape. It is also used in the processing of high-level nuclear waste, where the waste is immobilised in the glass through a process known as vitrification (contrast with Synroc).

Optically, borosilicate glasses are crown glasses with low dispersion (Abbe numbers around 65) and relatively low refractive indices (1.51 - 1.54 across the visible range).

Unexpectedly, use for Pyrex grew outside of scientific and industrial circles. New lampworking techniques led to artistic uses. Often the art can be refined and then rapidly-produced turning it into novelties that quickly degenerated into kitsch. There is a large market for cheaply reproduced trinkets, smoking pipes, bongs and other novelties. Borosilicate glass is sometimes used for high-quality beverage glassware; Bodum, Inc. markets a line of French coffee presses and double-walled beverage glasses made of borosilicate, lending them increased durability and microwave/dishwasher compatibility.

Further development in glassmaking continues to create new glass-ceramics that outperform borosilicate glass in various ways.

[Karen W.]

Yes I saw that.. I had know idea how old it was.. They said also that the older pyrex seemed stronger then the new stuff, and said they don't know if it has to do with company or inviornment from whence it comes from..

[neilep (OP)]

Well clearly they just do not make it like they used to.

[Karen W.]

 No they don't make much like they used to.. everything is meant to be disposeable , everything can be thrown away in the trash these days.. It's all about profit!

[daveshorts]

I heard that it may well be far older than this, as there is a description of a roman glass blower showing the emperor a new type of glass that was almost impossible to break. The emperor asked him whether anyone else knew the secret, he proudly said no, and then the emperor promptly killed him. This was becasue the emperor had a huge investment in glass and didn't want it to become worthless with the invention of a better type of glass...

Apparently there is only one thing you can add to glass to give it this sort of property and that is boron, so it is thought that the unfortunate glassblower invented pyrex. Unforutnately the intelectual property environment in the Roman empire was not really conducive to its wider adoption...

[neilep (OP)]

I heard that it may well be far older than this, as there is a description of a roman glass blower showing the emperor a new type of glass that was almost impossible to break. The emperor asked him whether anyone else knew the secret, he proudly said no, and then the emperor promptly killed him. This was becasue the emperor had a huge investment in glass and didn't want it to become worthless with the invention of a better type of glass...

Apparently there is only one thing you can add to glass to give it this sort of property and that is boron, so it is thought that the unfortunate glassblower invented pyrex. Unforutnately the intelectual property environment in the Roman empire was not really conducive to its wider adoption...

Silly Emperor...I would have ordered the revealing of the formula and then chopped off his head !!

[Karen W.]

Thats cool Dave Theres alot of history inthis stuff!

[Karen W.]

A wiser man indeed!! LOL

[eric l]

Studying chemical engineering, part of our practical work was working with glass, actually making or  repairing lab glassware.  (I was never really good at it, but that is beside the point here).  We never worked with Pyrex (™) but did work with Duran (™) which probably has a much lower boron content, and is easier to work with.
 
Anyway, in order to have some strength, the main thing was to heat up the complete piece after soldering or working at a small part, and then letting it cool at a very slow rate.  Sometimes we had to program the oven so that it took five days to cool from 500+ (°C) to room temperature !

I imagine that we did remain well on the safe side, that we could have gone twice as fast, but even then such long cooling times must be totally unacceptable to modern industrial processes.