My Mirror Rant

Mitch Miner

"So remember everytime you see a mirror, "do the fingernail test".

Now there is an obsessive-compulsive disorder for you.

We discussed this topic at some length earlier. The "short" version of our discussion . . .

Keys or a knife work much better than fingernails, and are handy for scratching the surface to warn the next person. If you find a spy mirror, at *least* do that.

The fingernail test will detect a first-surface mirror (one with the reflective coating on front) which is probably a "one-way glass" spy mirror. (Exception: the polished metal mirrors used in some restrooms are first-surface but not transparent.) First-surface mirrors are also detectable by smearing them, scratching them, and just looking at them.

One-way glass can also be made from a second-surface reflector, which will pass the fingernail test. In other words, the e-mail is giving a false sense of security, even as it spreads worry about spying eyes. (Come to think of it, this whole e-mail may have been started by a perv with a second-surface mirror and a fingernail fetish.)

Any one-way glass/spy mirror, whether first or second surface, has some characteristics that can aid in detection. It must have a hollow space behind it, big enough for an observer or a camera. The space behind it must be darker than the room it faces. It will not reflect as much light as a normal mirror. It can be seen through under certain circumstances.

So, instead of using your fingernails, use your keys on the mirror, thump the mirror to see if it is solidly mounted, cup your hands around your eyes to block out light and look through it, shine a flashlight or a laser pointer (careful!) through it as you look through the glass, and learn to estimate how much light the mirror should be reflecting.

A word of warning, though. There is at least one method of spying through a mirror that would be nearly undetectable. I don't think we need to publicise that right now. Suffice it to say that the fingernail test would not detect it.

There may be prying eyes behind any mirror, but certainly not behind every mirror. The fingernail test is not a very good method of detecting spy mirrors. The e-mail is scary, but at the same time falsely reassuring. Use some sense.

Go to Classic Debunkings  Index