Q. What is the difference between transparent and colored glass?

A. Window glass, mirrors and tableware are indispensable for our daily life. While windows and mirrors are made from transparent glass, other glass and tableware may be a variety of colors. Ordinary glass (called soda lime glass) is made by heating a mixture of silica (the sand found on a beach), sodium carbonate (contained in ash of burned trees and grasses), and calcium carbonate (a component of limestone and chalk) until it becomes a liquid and then cooling it. Unless there are impurities in the raw materials, transparent glass is the result. To make colored glass, metal oxides are added, which combine a metal and oxygen. To get the color of blue, cobalt oxide and copper oxide are added, while chrome oxide and iron oxide are added to get the colors green and yellow, respectively.