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This section of mirror doesn't fog
(lemmy.world)
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this post was submitted on 24 Sep 2025
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Mildly Interesting
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Suppose you were in this situation and suspected something. I’d imagine the space behind it would be totally dark, so what would be a safe way to check if there’s a gap in between without breaking the glass?
there are no "one-way" mirrors. You just need to make your side darker than the other side (there's a reason the observation side of a two-way mirror is never brightly lit, but the interrogation room is)
Tldr: put your face right up against it and use your hands to block out as much light as you can
15 upvotes? Really? Mirrors are painted on the back with opaque paint.
Are we cross posting this to a flat earth science forum?
but a one-way mirror (also known as a two-way mirror) is one that you can see through in one direction
I read a long time ago that putting something flat against the mirror will show you. I think if the mirror is legit you’ll see the reflection directly on the surface, if it’s two way the reflection will look like it’s inside the glass.
But I’ve never had the chance to actually test that, so take it with a grain of salt.
Edit: Turns out this is incorrect; thanks to everyone for educating me!
It would be the other way around, if at all.
"First-surface" mirrors where the reflective layer is on the front of the glass are quite fragile, so wouldn't typically used for residential applications (you'd remove the reflective coating by cleaning it).
A regular mirror has the reflective surface on the back of the glass (which is then is further coated with a protective paint), leading to the effect you describe.
I don't however know enough to say one way or the other whether a surveillance mirror would becessarily be a first-surface mirror.
Just checked my bathroom mirror and it looks to be a first-surface mirror
This is ancient advice for two-way mirrors, IIRC nowadays even legit mirrors can reflect directly from the front instead of the back. In this age of spy cameras this is mostly irrelevant.
Another tip was shining a bright light to illuminate the supposedly dark room on the other side, which again, would be way more expensive than a smoke detector spy camera.
Yes, darkening your room and then pushing a bright light up against the one-way, taking care to not have it leak into your room, should make the other room brighter so you can see it.
Not that this is a one-way mirror anyway.
scientific use mirrors are front mirrors, the metal is deposited on the outer surface. They are delicate and difficult to clean.
Every household mirror is rear coated, and then painted to protect the metal from oxidation.