Have you tried Krylon’s Looking-Glass spray paint? It’s an easy way to make faux-mercury glass decorations for the holidays using inexpensive pressed glass.
Although I had lofty ideas of painting plastic pumpkins, for successful results the paint should only be used on clear glass objects like bowls, vases, picture frames and candlesticks. When sprayed on the reverse side of an object, the paint dries to a dull finish then reflects a mirrored-like shine on the opposite side. (This product is for decorative use only and should not come into contact with food.)