What causes foxing on old mirrors?

Foxing occurs when air and moisture penetrate behind the glass and react with the silvering or mercury backing over many decades. This chemical process causes the reflective layer to break down into characteristic dark spots and cloudy patches.

How do I clean an antique foxed mirror?

You should use only a soft, dry microfiber cloth to gently remove dust from the glass surface. Avoid liquid cleaners and modern chemicals, as moisture can seep behind the plate and accelerate the deterioration of the original backing.

Are foxed mirrors fragile?

The glass plates are often thinner and more delicate than modern equivalents, requiring careful handling during movement. The aged frames, particularly those made of gesso and giltwood, can also chip if subjected to knocks.

How do I date a mirror frame?

Dating relies on identifying the construction methods, wood types, and decorative styles characteristic of periods like the Regency or Victorian eras. Examining the backboards, fixings, and the nature of the glass plate provides further clues to the age of the piece.