The Causes of Black Spots on Mirrors

Chelsea Fitzgerald

Mirrors can make your home appear larger and give it an elegant style. Black spots caused by improper care detract from these accent pieces. Utilizing the reflective aspects of a mirror creates visual space.

Improper care causes black spots in mirrors.

Positioning a mirror in your home or other building so that it reflects a lovely view, an architectural feature or a cherished belonging multiplies the appeal. Whether you have a vintage mirror or you are purchasing a new one, ilearn how to care for it to prevent worsening or the appearance of new black spots.


Check your mirror before installing it to ensure that no moisture is on any of the surfaces, particularly the backing. This occurs due to temperature changes during shipping and condensation may develop. Dry the surface and backing with a soft, lint-free towel and then allow it to air-dry thoroughly. Over time, moisture can stain the face of a mirror or disintegrate the backing. Avoid hanging them in areas with high humidity, such as near water or steam pipes.

Wash any areas exposed to foreign elements, such as road salt, from the mirror surfaces. Do this with a cleaning cloth saturated with warm water and then wring it out well. Dry the surface thoroughly after the cleaning.


The occurrence of black spots and lines around mirrors happens less frequently now than in the past due to an improvement in mirror coatings. Use gloves when handling and hanging mirrors to protect the mirror from chemicals and to protect your hands. The chemicals and body salts on your hands cause damage to the backing, thus resulting in black spots. Clean mirrors with warm water and a soft, lint-free cloth. Using a window cleaner also works well, but avoid allowing the cleaner to puddle or remain on the surfaces over a couple of minutes. Prevent puddling by spraying the cleaner directly onto a cloth, never the mirror surface. Avoid cleaners with a heavy ammonia base, this damages the backing and mirror edges.

Temperature Changes

Cyclical changes in temperature causes black spots on mirrors. Avoid storing them in outdoor or unheated areas. This results in the mirror surfaces to contract and expand with the changes in temperature, thus causing damage and unsightly spots.


Never hang your mirrors flush with a wall surface, if you can prevent it. Leaving a small space between the mirror and wall allows adequate ventilation. This helps it to stay dry during humid weather conditions. (see ref 2 bullet 7 under Installation) Coastal regions of the country present problems with the silver backing on the mirror oxidizing and resulting in black spots, so it is particularly important to have adequate ventilation in these areas of the country.