Thoroughly scrub glass surface with #000 or #0000 steel wool and rubbing alcohol. Next, clean glass surface with rubbing alcohol and clean new paper towels until dry. Make sure glass surface has a squeaky clean feel/sound while being wiped dry.

Is Back Painted Glass Tempered?

Generally back painted glass is not tempered (just like glass mirror). Tempered back painted glass is only recommended if the glass will be subject to fast temperature fluctuations like behind a stove or cook top, as well as in front of a fire place etc… If your application requires tempered glass, the glass must be tempered before painting.