How “etching of glass” is done?

Take the glass piece on which etching is to be done.

Coat it with wax.

Now use a pointed substance to draw the design to be etched.

Now pour the HF liquid are pass HF vapours over the piece.

The exposed surface, without wax ,having design will react with HF

Glass contains silicates of Ca and Na which react with HF forming water soluble as well as volatile substances which can be removed by washing.

The non-exposed portion doesn't react as wax does not allow it to.

Thus we get and etched surface.