Antique mirrors show not only what is represented in them but their own history. Most are silvered; some are covered with mercury. All may have dark and spidered locations, dark spots that look like smudges, foggy sections that seem smeared. The imperfections of your antique mirror glass are a true part of its appeal and an important part of its value. You need to keep it clean, but only surface smudges should be wiped off.

What is at a Smudge

That blurry imperfection that looks like a dried finger mark or grease could be a fault in the aged silvered back of the mirror. A mirror hanging up where moisture can be trapped between the wall and the mirror financing will begin to deteriorate, look cloudy, and develop spots where the silvering has decomposed and come off the mirror. The damage may also have been induced during a move or by a poor original application of the silver to the mirror back. Wash the mirror surface, and then shine a light straight on it to show issues with the silver backing. A precious antique is well worth a trip to a specialist restorer to determine whether you should have the bit re-silvered, or appreciate its age and leave it alone.

Smudge Solution

Wash the mirror glass — not the back — by hand and with a spray cleaner to be sure no harsh chemicals causing more harm than clarity on your prize. Mix 1 part rubbing alcohol with 2 parts water. Dampen a clean rag with the solution and rub only the glass until the surface dirt and smudges disappear. Substitute white vinegar if you don’t have alcohol. Prevent all abrasive cleaners — even washing soda or baking soda may be too unpleasant for the fragile glass.

Frames, Gilding and Gesso

What cleans the surface of your antique mirror can eat the framework. Old mirrors in original frames are probably gilded, and their ornate curlicues could possibly be built with applications of gesso to the engineered wood, overlaid by clay bole and then gold leaf. Water-gilded bits were produced by placing the gold leaf directly on the wet clay. Oil-gilded means the gesso was implemented with oil and the stone stuck to the petroleum. In any instance, obtaining the gold framework wet may dissolve the water-gilded gold leaf or even collapse the gesso that facilitates the oil-gilding on the framework. A simple home cleaning solution can harm the framework, requiring repair and regilding. Never spray cleaner to a framed antique mirror. Use the solution to your lint-free fabric and rub the glass, avoiding all contact with the framework.

Mirrors and Mercury

Truly old mirrors, beginning from the 16th century, were silvered with a fluid mercury amalgam that can emit toxins if released into the environment. The practice fell from favor and was eventually discontinued in the mid-19th century, when mercury was replaced with silver nitrate. But if you suspect or know that your mirror includes mercury, be extremely careful when handling it and worry less about aged cloudy areas on the glass than scraping or dislodging a brittle mercury backing. Necessary light dusting and gentle wiping with a moist solution that is not permitted to seep into the frame can keep your mirror clean. But any indication of metal flaking or corrosion on the silvery backing should be assessed by an expert.