Borosilicate Glass

Most of our products are made from borosilicate glass: Pyrex 7740, Kimax KG-33, Schott Duran, or Kavalier Simax, all of which are functionally equivalent. Borosilicate glass is useful for lab use primarily because of its low thermal expansion. This allows us to heat the glass locally without exceeding the strength of the glass due to expansion, meaning we can construct elaborate glass apparatus without it shattering. This also means that you can heat and cool it without damage. Our standard borosilicate glass has a linear coefficient of expansion of 32.7 x 10-7 cm/cm/deg. C. There are other borosilicates having higher expansions, for other specific purposes, such as vials and syringes.

Much of our "raw" material comes in the form of tubing , or as "blanks" in a number of shapes such as round bottom flasks, erlenmeyer flasks, carboys, media bottles, etc. These we modify and transform, most commonly by heating. For example, see our page of end finishes we routinely provide, including firepolishing, lapping, and tooling to specific forms.

Tubing and apparatus can withstand vacuum well, within the constraints of good design, because the glass is under compression. Under pressure, the surface is under tension, so there is greater danger of explosion. Apparatus for pressure require heavier walls and care in use. See a nomogram of pressure versus diameter of tubing, pdf courtesy of Kimble Glass. This is because the strength of glass is very high in compression; much less so in tension. Much of the tensile strength resides in the condition of the surface of the glass - if the glass is scratched or abraded, its strength goes way down. We routinely capitalize on this aspect of glass to cut tubing accurately and cleanly; it's the cylindrical equivalent of scoring flat glass for windows or stained-glass art. We can coat glassware with a thermoplastic covering to protect the surface, and to contain the contents and shards in case of disaster. We do this commonly on apparatus for vacuum, such as condensers and receivers for rotary evaporators.

There are a number of surface treatments for glass such as;

• Organometallic coating; see a sample of gold coating.

• Amberizing for light sensitive compounds. Some sizes of borosilicate amber tubing are now available as well.

• Tempering for strength

• Etching and sandblasting; for a frosted appearance.

• Decaling

• Adhesives; see links page for suppliers and their information.

You can find more detailed information listed at the websites of the major manufactures of borosilicate glass, including optical and chemical characteristics;

Schott Glass

Corning

And in an entry in Wikipedia for borosilicate glass

If you are seeking information about quartz glass, GE Quartz provides good technical information.

The Corning Museum of Glass also has good descriptions of other glass types such as soda-lime glass, lead glass, etc.