I know I can buy a smart mirror already finished for around $80, but I think building one myself will be an interesting project.

That being said, I read somewhere (this may not have been a dependable source) that a two-way mirror should be used for this because it is transparent UNLESS an opaque black material is behind it, then it just looks like an actual mirror. Would a two-way mirror behave the way I explained above or should I use a different material for a smart mirror?


1 Answer 1


Yes, a two-way mirror works the way you explained.

In more detail, a mirror is a thin sheet of a reflective metal. This is usually supported by being attached to a piece of glass (and often protected by being covered on the back), but the actual mirror is the metal layer.

A two-way mirror reflects some proportion of the light, and lets the remainder through. If it is placed between a brightly lit room and a dark room, it looks transparent in the dark room (showing the light room), and reflective in the light room (also showing the light room).

If you put a two-way mirror over a display, the mirror will look reflective when the display is off, but show the the display (if it is bright enough) when it is on.

  • The contrast and color rendition of the display usually suffers quite a bit when behind the two way mirror film. I suspect getting a high quality film is the biggest challenge.
    – JPhi1618
    Nov 25, 2019 at 15:29

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