Glass is a material made mostly of silica, but also mixed with soda ash and limestone and it is formed at temperatures in excess of 1700 degC. The resulting product is hard and brittle and typically transparent. A unique feature of glass is that it retains some liquid and some solid properties in its final form. It is known as an amorphous solid.
Sometimes other elements are added to the glass in manufacturing in order to enhance its properties for specific applications. Adding boron oxide makes an oven proof glass, lead oxide makes a fine crystal glass, laminating glass and plastic layers together make a bullet proof compound and toughened glass can be made for car windshields and other applications by cooling the glass quickly during manufacturing. Waterjet cutting can be used on glass without shattering or cracking the surface.