A two-way mirror is a piece of glass coated with a substance called micro pane. If you stand on the treated side, you see your reflection but the untreated side looks like a tinted window. If you see a wall behind the mirror, it’s a good bet that it’s nothing more than a regular mirror.
For a two-way mirror to be effective, the light on the mirrored side needs to be 10 times brighter than the light on the other side. If the lighting is any dimmer, it’s possible to see through the glass to the observation area.
The use of two-way mirrors is closely tied to issues of personal privacy and Constitutional rights. Most states have passed additional legislation preventing the use of two-way mirrors in rest rooms, locker rooms, showers, fitting rooms and hotel rooms. [3] X Research source For example, according to the 2006 New York Code, if a location in that state has chosen to use two-way mirrors for surveillance, they are required to post signs that notify you. [4] X Research source Many places, such as gas stations, will use one way metal mirrors because glass mirrors can be destroyed by users. If the mirror in question is metal, then it is not a two-way mirror.
The sound of tapping a two-way mirror has also been described as bright or sharp as opposed to a thud from an everyday mirror. [6] X Research source
Due to variables like lighting and the material with which the mirror is manufactured, it can be really difficult to tell whether you are truly touching your reflection or not. You might think you’re touching a first surface mirror when you’re actually not. Also, it’s possible for a two-way mirror to be a second surface mirror. If other aspects of the situation, like the mirror’s setting and lighting, have indicated that what you’re seeing is a two-way, don’t let the fingernail test be the deciding factor.
