Can I place these mirrors over a working fireplace?

Historically, overmantel mirrors were designed specifically to sit above operating fireplaces to reflect ambient light. The robust construction handles normal room temperatures. Excessive direct heat from unmanaged fires can dry out wooden frames and crack gesso over decades. Maintaining adequate clearance above the mantel protects the antique finish.

How do I clean an antique gilt frame?

Dust the carved surfaces gently with a dry, soft-bristled brush to remove surface particles without damaging the delicate gold leaf. Avoid liquid cleaners and chemical sprays entirely. Moisture can dissolve historic water gilding and soften underlying gesso layers. Professional conservation is necessary if the surface requires deeper cleaning.

What is mercury glass?

Early mirror plates were backed with an amalgam of tin and mercury poured behind the glass. This traditional process yields a distinctive, slightly distorted and atmospheric reflection. As the backing ages, chemical reactions create characteristic dark spots known as foxing. Modern silvered plates replaced this technique in the later nineteenth century.