Preventing “Black Back”
on Mirrors
The discoloration often found at the
bottom of a mirror is oxidation of the metallic coating on the back of the
glass. (usually silver or aluminum) The oxidation is often cause by contact
with chemicals and water. (ammonia and citric acid in cleaners) During the
installation of a mirror it is helpful to rest the mirror on small neoprene or
polycarbonate setting block. These blocks (usually 1/8” thick) provide airspace
under the mirror to promote the disbursement or evaporation of water and
cleaning products. Although the setting blocks are usually clear; j-channel can
be used to hide the setting blocks while offering many choices in anodized finishes
that can complement the mirror .
In the event your mirror is already
installed and the setting blocks are not present, it is crucial that you use
the correct cleaning product and techniques to lengthen the life of your
mirror . I recommend using a foaming ammonia free glass cleaner (Sprayway
catalog # s50) in order to prevent the cleaner from running down the face of
the mirror and coming in contact with the backing of the mirror . If you use ammonia
based cleaner, spray the cloth not the mirror. Sprayway glass cleaner can be purchased at
Fast Glass Mirrors & More (770 428 0819) or at many Ace Hardware stores.
Quick tip– for tough spots on a mirror face, try xxx steel wool. Make sure the steel wool has not been used
before and that it has no rust that could scratch the mirror .