If an object does not absorb or reflect light, then the object is transparent. This is the main reason why glass is transparent. Glass is a type of covalent compound consisting mainly of silicon and oxygen. We know that in a covalent compound, the electrons in the outer orbit of the atom are very tightly bound , so it is very difficult to deviate them from their position. As a result, when energy (photons , heat , electricity, etc.) falls on the electrons of the glass, the electrons are not stimulated in any way. That is, the electrons inside the glass do not absorb or radiate any energy. Neither black , nor white , nor anything else.