Caring for a Mirror: Cleaning, Humidity and the Black Edge

A wall mirror should outlast most of the furniture around it. The things that shorten its life are almost all avoidable, and almost all happen during cleaning.

Clean the cloth, not the mirror

Spray the cleaner onto a microfibre cloth rather than onto the glass. Liquid sprayed at the mirror runs down and collects at the bottom edge, which is exactly where the silvering is most vulnerable. Wipe with the damp cloth, then follow immediately with a dry one.

What not to use

• Ammonia-based cleaners attack the backing paint and the silvering at any exposed edge.
• Abrasive powders and scouring pads scratch glass permanently.
• Newspaper, despite the folklore; modern inks smear and the paper is more abrasive than it feels.
• Soaking of any kind, particularly on frameless or bevelled mirrors where the edge is exposed.

Warm water with a very small amount of dish soap, followed by a dry microfibre cloth, handles almost everything. For hard-water spots, a cloth dampened with diluted white vinegar works, kept well away from the edges and dried immediately.

The black edge

Dark mottling that creeps in from the perimeter is moisture that has reached the reflective layer from the edge and lifted it. It is most common in bathrooms and in mirrors mounted flat against an outside wall with no air gap. It cannot be cleaned off and it cannot be repaired, because the damage is to the coating rather than to the surface you can reach.

Slowing it down

Ventilate the room. Wipe the bottom edge dry. Where the fixing allows, leave a small air gap behind the mirror rather than sealing it to a damp wall. If a mirror is going into a bathroom with no window and no working exhaust, expect a shorter life from it regardless of what it cost.

Frames want different treatment

Wood and rattan frames should be dusted dry and never soaked. Metal frames take a damp cloth well, but check whether the finish is lacquered; an unlacquered brass frame is meant to patinate, and polishing it back is a decision rather than maintenance.

Moving a mirror

Carry a large mirror vertically on its edge, never flat, and never by the frame alone on a heavy piece. Flat carrying flexes the glass across its widest span, which is how mirrors crack on the way to the wall rather than on it.