Facebook
Borosilicate Glass is best known as Heat Resistant Glass! 


Borosilicate glass is a glass in which some of the silica, or SiO2, is replaced by borate, or B2O3. This gives this type of glass certain properties, different from the ‘normal’ soda-lime glass, from which the most well known is the heat resitance.

Borosilcate glass was invented by the famous German scientist Friedrich Otto Schott (1851–1935), who gave the world of glass not only borosilicate glass but he was also the one, in the later 19th century, who created the fundamental principles of the modern science of glass and glass technology. 
Frierich Otto Schott




Otto Schott founded a glass technology laboratory in Jena in 1884, together with Carl Zeiss and Ernst Abbe under the name “Schott & Associates Glass Technology Laboratory”. 

Otto Schott developed improved types of optical glass and besides he concentrated on melting of new types of technical glass. 

Then in 1887, he made a revolutionary discovery. He melted a glass with high chemical resistance and high resistance to thermal shock, something he had never seen before. 
With this invention he changed the world.   
  
Duran laboratory glass is found in almost any laboratory around the world (Schott)



Chemistry, at those times still in the starting phase, suddenly had a new tool with which it was possible to do things which were out of the question before this invention:

- The borosilicate glass chemical resistance very good to most chemicals, so the glass can be used as an inert reaction vessel for chemical reactions. 
- Borosilicate glass is amazingly resistant to thermal shocks (sudden temperature changes of up to about 210°C can be accommodated). 
- It has a high heat resistance so it can be heated up easily without breakage (chemical reactions at elevated temperatures in an inert vessel). 
- It is also impervious to gasses so reaction vessels were air tight (protection against oxygen from air) and vacuum tight (chemical reactions under lower pressures).
very smooth, non-porous surface prevents the adhesion of fungi, bacteria etc.
easy to clean
taste and odour-neutral
Some remarkable and useful properties!!!

Borosilicate glass chemical resistance

Borosilicate Glass is highly resistant to water, neutral and acid solutions, concentrated acids and acid mixtures, and to chlorine, iodine, bromine and organic substances.Therefor it is the preferred material compared to most metals and plastics. In general chemical reactions over longer time can be done at elevated temperatures up to 95°C without a problem.
It must only be avoided to heat up phosphoric acid and (stronger) alkaline solutions.


Schott household glassware


Not only Chemistry benefitted from this invention but the frontiers of science were pushed out for many fields like Biology. Physics, Medicine, and Astronomy. 
The invention brought Schott & partners world fame and the company florished.
Today the Schott Group is still active and has production locations in 43 countries and sells many products made out of borosilicate glass (among other glass types).  




The most famous brand name made out of Schott borosilicate glass is Duran. Duran is a worldwide well known brand for laboratory glassware made out of borosilicate glass. Not only is the quality of Duran laboratory glass very good, the brand has also a very wide range of products.
All lamp blowers and glass artists know Schott Boro Artistic, from their tubing and rods. The glass tubings and rods come in an extremely wide range of dimensions.

Schott glass tubing


Schott glass rods


Schott's special flat glass: Borofloat
















Schott even has a float glass, Borofloat, made out of borosilicate glass which has the outstanding properties due to the composition, but also because of the production technology used which gives Borofloat glass an excellent transparency. Borofloat glass  is even an excellent material for Subsurface Laser Engraving while normally only optical glass can do the job. 
(Here you find a nice article about  subsurface laser engraving.)     
The typical chemical composition of borosilicate glass is:

        SiO2 = 80.6% 
        B2O3 = 13.0% 
        Na2O = 4.0% 
        Al2O3 = 2.3%
 


Another company who has a long history with borosilicate glass is of course Corning Inc. 
After Corning Glass Works developed Pyrex, the brand name, in 1915, it became a synonym for borosilicate glass in the English-speaking world. 
Pyrex ovenware



However, the brand Pyrex was later on (late 1930’s) also used for tempered soda-lime glass which was also used for ovenware. 
This has led to a lot of misunderstandings and the discussion is still going on. Most American producers of bakeware use tempered soda-lime glass and say that it is due to better mechanical properties. This tempered glass breaks into relatively small pieces (some may be larger) generally lacking sharp edges and shards when it does break. Others say that the most common breakage is due to heating stress in the oven so borosilicate is a better material because it can withstand thermal shocks.


One thing is for sure the production of tempered soda-lime glass bakeware is cheaper than the production of borosilicate ovenware!!!

Another thing is unfortunately also true, there have been some scary reports about Pyrex glass exploding while baking food in the oven. People who openend an oven door were treated with a shower of shattering pyrex. The Pyrex products used during these incidents were all made out of tempered soda-lime glass and not borosilicate glass! 
It is clear that these incidents all happened because of the fact that tempered soda-lime glass doesn't have the superior heat shock properties of borosilicate glass. A thing to remember when buying your new ovenware cause nobody wants exploding glassware in his kitchen!

 
Simax teapot


The company Kavalierglass may not be forgotten when talking about borosilicate glass. This Czech company has also been pioneering in the field of laboratory glass and bakeware in the 19th century. Nowadays the company has the brand Simax for its borosilicate glassware. 
Simax has an outstanding color, in fact no color, and many lamp blowers who make art work prefer Simax rods and tubing for that reason. 
Kavalierglass brings also bakeware and kitchenware made out of Simax borosilicate glass on the market.