[SOC] Two Way Mirror .... continued

[Hank Kohl K8DD]

 From http://urbanlegends.about.com/library/blmirror.htm
Archive of legends and folklore


I'll tell you straightaway that, despite the overemphatic tone used in the 
above text (which is of course what keeps it in circulation), the 
fingernail test does work as described in most situations. But allow me to 
clear up a few fuzzy points involved, as well as suggest several other 
possible ways to identify a two-way mirror.
For the sticklers among us:
Some companies in the window-glass and mirror trade call them "two-way 
mirrors" and some call them "one-way mirrors" � don't ask me why; there 
seems to be no distinction between the two names. They both refer to a 
product known as Mirropane. Promotional literature from the LOF 
Architectural Specialty Glass company states that the product registered 
under the name "Mirropane E.P. Transparent Mirror" is "formed using LOF's 
patented chemical vapor deposition process on 1/4" Grey tint glass." As to 
exactly how that works or even what reflective metal is involved, it seems 
to be a trade secret, although the good folks at Morehouse Glass in 
Portland, Oregon suggest that tin or nickle are the likeliest choices. It's 
probably not silver, as suggested in the missive under scrutiny. The 
product can be heat-treated for maximum strength and can also be laminated 
to make it scratch resistant (so if, say, some nut decided to use this 
product for a mirror in a changing room, it would not be easily scratched 
by a belt buckle or other light brushings-up-against). The product can also 
be made considerably bullet-proof, in case you are thinking about buying 
some for the watchtower in the maximum security prison you've just had built.
For those who "just want to know":
Sure enough, Mirropane is treated on the "subject" or first surface of the 
glass, and the recommended lighting ratio for surveillance purposes is 
10:1, with the Subject side being ten times brighter than the Observer 
side. The fingernail test described above works for the very reason stated, 
namely that there is no glass between an object and the reflective surface 
if the mirror is touched. There are other first-surface mirrors as well 
that are not two-way, but these are used primarily in precision optical 
instruments or in scientific experiments using lasers, where the refraction 
from the glass would be an interference. Mirropane is commonly used in 
prisons and police stations, in psychological observation rooms and in 
security situations which can include many types of businesses where 
viewing customers or employees is deemed necessary or desirable.
For those who possess persistent curiosity:
Here are some other ways to identify Mirropane from an ordinary, 
second-surface mirror.
This from William Beaty, electrical engineer, Seattle [www.physlink.com]: 
"... simply turn the lights off in [the] room, then place a bright 
flashlight against the mirror surface. If there is a hidden chamber behind 
the mirror, the flashlight will illuminate it, and since you're in a 
darkened room, you'll see the hidden chamber."
A deputy from the Washington County Police Department in Oregon concurs, 
and suggests that even a pen-light will work for this test, though not 
nearly as well. He further suggests that, if you are in a room (such as a 
changing room) where you cannot turn off the lights on your side, if you 
hold your eyes near to the glass surface and cup your hands around them on 
either side to eliminate most of the light from your visual field, you 
ought to be able to see through the treated glass, as Mirropane will permit 
about a 12 percent passage of light (from the lit side to the hidden 
chamber, if there is one).
Douglas Brown, a part-time field researcher and writer who also works for 
Powell's Books, Inc. in Portland, Oregon, has some clever advice to share. 
He makes the point that there is a clear auditory difference between 
Mirropane and regular mirrors, because of how they are installed. Rap on 
the surface with your knuckle or fingernail, he says, and in most 
situations you'll be able to hear the difference in the sound produced. 
Ordinary mirrors have backing material which will dull the sound, while 
windows have open air behind them and will reverberate more.
Along similar lines, when the text asks "how many of you know for sure that 
the seemingly ordinary mirror hanging on the wall is a real mirror, or 
actually a 2-way mirror?" those employees of Morehouse Glass make the point 
that any mirror hung in front of a wall will be a mirror plain and simple, 
because Mirropane will be a pane of glass installed into the wall like any 
other window, and will have window framing evident, not mirror glass 
molding around it.
For those who will remain nervous nellies from here until breakfast:
This article is not meant to be encyclopedic. We'll leave that to the 
special effects department. Common sense would seem to dictate, however, 
that one be clear about where and why one is undressing in any potentially 
semi-private place, rather than concerning oneself with who may be 
watching. Birthday suits are, after all, just birthday suits.

Peter Kohler is a writer and researcher based in Portland, Oregon




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