Answered By: Beth Hylen
Last Updated: Oct 31, 2016     Views: 10

Dear Friend,

I am sending information compiled by Dr. Robert Brill, CMoG Research Scientist Emeritus:

There are many different kinds of glass.  Glass is best described as a state of matter, not as a compound or mixture having one special chemical composition.  Literally hundreds of thousands of glasses with different chemical compositions have been made, and each of them has its own set of physical properties as determined by its own chemical composition.  Even so, they all share certain properties in common that are the result of their having similar structures at a molecular level.  Glasses combine some of the ordinary properties of crystalline solids with some of the properties of liquids but without being either crystalline solids or liquids.

Most glasses that would be familiar to you contain certain elements.  These elements are usually described in terms of their oxides.  Those most commonly used are:

  • Si, silicon.  The oxide is SiO2, silicon dioxide.  Ordinarily the SiO2 is introduced as sand. 
  • Na, sodium.  The oxide is Na2O.  It is introduced as a white powder called soda ash.
  • Ca, calcium.  The oxide is CaO.  It is introduced as limestone, a mineral.
  • Pb, lead.  The oxide is PbO.  Lead oxide in a glass makes it shiny, brilliant, and heavy.
  • K, potassium.  The oxide is K2O.  Potassium can be used in place of sodium as a "flux", a substance that allows the sand to be melted at a lower temperature.

Many other elements are used to make glasses with special properties. For example, the following elements can be used to make glasses with the colors described:

  • Fe, iron.  Colors glass green.
  • Cu, copper.  Colors glass light blue.
  • Mn, manganese.  Colors glass purple.
  • Co, cobalt.  Colors glass dark blue.
  • Au, gold.  Colors glass deep red, like rubies.

Does this answer your question? Please let me know if you have additional questions.

Sincerely,