Thanks for posting.
It is important to consider that the coating liquid is masking the etching or stain on the glass, and is not removing it.
Bottles buried in the ground actually decompose in a sense...a portion of the glass leaches away from the surface leaving behind (frequently) white deposits. The only way to remove the dullness or whiteness is to polish the glass. Typically this is done with tumbling process somewhat like rock tumbling.