One Way Mirror

One Way Mirrors by Laminated Glass NYC
One Way Mirrors by Laminated Glass NYC

A one-way mirror, also called two-way mirror (or two-way glass) and semi-transparent mirror, is a reciprocal mirror that is partially reflective and partially transparent. The perception of one-way transmission is achieved when one side of the mirror is brightly lit and the other side is dark. This allows viewing from the darkened side but not vice versa.

A true one-way mirror that actually allows light to be transmitted in one direction only without requiring external energy is not possible as it violates thesecond law of thermodynamics: if one placed a cold object on the transmitting side and a hot one on the blocked side, radiant energy would be transferred from the cold to the hot object. Thus, though a one-way mirror can be made to appear to work in only one direction at a time, it's actually reflective from either side.


The glass is coated with, or has encased within, a thin and almost-transparent layer of metal (usually aluminium). The result is a mirrored surface that reflects some light and is penetrated by the rest.

Light always passes equally in both directions. However, when one side is brightly lit and the other kept dark, the darker side becomes difficult to see from the brightly lit side because it is masked by the much brighter reflection of the lit side.


A one-way mirror is typically used as an apparently normal mirror in a brightly lit room, with a much darker room on the other side. People on the brightly lit side see their own reflection—it looks like a normal mirror. People on the dark side see through it—it looks like a transparent window. The light from the bright room reflected from the mirror back into the room itself is much greater than the light transmitted from the dark room, overwhelming the small amount of light transmitted from the dark to the bright room; conversely, the light reflected back into the dark side is overwhelmed by the light transmitted from the bright side. This allows a viewer in the dark side to observe the bright room covertly.
At Giovani Glass we specialize in manufacturing one way mirrors for your home, office, institution, subway facilities and much more.

(929) 888-7059
New York, USA