One way glass, which is what this is, are just exactly what you see in TV and movies when the cops are questioning suspects. You can see them, but they can’t see you, as to them it’s a mirror. However, these have one BIG flaw. The light on the mirror side MUST be brighter than the light on the other side, otherwise the mirror effect disappears. One way glass is not a prefect mirror, a portion of the light shows through, hence the shadows shown in the photo of the inside.
The other problem with one way glass is it’s not perfect. If someone were to come close and shield their eyes to create darkness around the area looking at the glass, they would see inside as now it’s darker outside. The only way to prevent this is to double layer the glass (with a decent gap between), and to really make it safe, have it lighted inbetween the layers. This, with enough light, might even make it safe for night use, but I wouldn’t bet on it.
To answer GWC’s question… It’s not a perfect mirror, light does get through. Your eyes can only see what is brightest (reflected back), the interior light showing through is way too dim in comparison for the human to discern. A similar effect is seem with tinted glass as well. Seeing in a buiding with tinted glass in broad daylight is extremely difficult, especially with heavy tinting, but at night with the interior lights still on, it’s easy to see inside.
Using high quality electronic imaging equipment and a good threshhold software filter (filter out all light above a certain brightness, then enhance what’s left over to be brighter) MIGHT reveal the interior, but that would take some seriously sensitive and expensive equipment (far out of a pervert’s budget).
shittin ell. i had a sesh on one of these. it was in London for a few days. only a number 1 mind ^p.s sparky it was closed at night. and i had a good ol look at the glass. about half inch mirrored. couldnt see my hand at point blank