what other substance do you heat limestone and sand with to make glass?

Answer 1

Oxygen is required to keep the heat VERY high and burn off any impurities.

Answer 2

Depending on the type of glass you want to make. They are various type of glass in industry as you know, say from soda-glass (the "regular" glass used to make windows, cheap water glass, etc), boronsilicate glass (or well known as "pyrex"), lead glass (used to, say to make expensive wine glass or crystal), and many others.

The basic ingredients to make glass is silica and sodium carbonate (soda ash), and limestone. That mixture will give you regular soda-glass.

If u want to make pyrex, usually about 10-15% Boron, usually as borax, Na2B4O7 is added. Sometimes, a little bit of aluminum salt is added to the blend.

I u want to make lead glass, lead (II) oxide, PbO or litharge is added to the mixture.

If u want colored glass, various metal salt is added to the mixture to give colors. Cobalt oxide for example, gives you that nice blue "cobalt" glass.

Answer 3

CaF2 - fluorite
Borates - salts of B