razor blade works well
If it has etched the glass,there is no way to remove it.
Mirrored glass often has a layer of paint over the mirroring materials. You would have to remove this first using a standard paint stripper. You would then use a chemical, such as muriatic acid or bleach to remove the mirroring.
Does paint come off glass?
To paint glass lamps that have already been painted, you should first cover the light bulb socket and cord of the lamp with painters tape. You can then paint the glass lamp with Krylon Fusion paint. It is designed to adhere to glass and other slick hard to paint surfaces.
To paint on glass you will need special paints, which will not streak, but will let light through.
Just add as much glue to the paint as necessary. The glue will change the opaque-ness of the colour.
You can try Krylon Looking Glass Mirror-Like paint or silver spray paint.
paint and glass
Any good craft store in your area should have Gallery Glass paint as well as one or two other brands. If they do not, ask if they will special order them in for you.
Depending on what you want to accomplish, either faux stained glass paint, or any commercial paint formulated for glass. Craft stores sell many brands of both
The detailing of a clay bar is an engineered resin compound. It is designed to remove contaminants from the surface of one's vehicle's paint and glass.
Paint thinner will remove it.