Two Way Mirror FAQ

Two Way Mirror FAQ

How does a two way mirror work?
A two way mirror, a mirror that is transparent on one side and reflective on the other, is created by placing a layer of semi-transparent film of aluminum on an acrylic substrate. This allows a percentage of light to pass though and reflects the rest.

We've all seen a cop drama TV show or film in which a criminal suspect is interrogated while police watch from behind a mirror. Why can't the suspect see those watching him behind the mirror? The answer lies in the level of lighting in both rooms. The room the suspect is in is kept very brightly lit, so that the light in the room reflects off the mirror's surface. The observation room containing the police, on the other hand, is kept dark, so that little to no light gets through the glass. As a result, the suspect sees only his own reflection and the police see into the suspect's room clearly. If the lights in the suspect's room were suddenly turned out, or the lights in the observation room suddenly turned on, then the two way mirror would become a window. It's the same sort of effect you see in a mirrored office building at night -- if there is a light on in one of the offices, you can see into that office just fine. The whole two way mirror effect is kind of like if you were to whisper in one room while a loud stereo played in another; your whisper might carry into the room with the loud stereo playing, but no one would hear it because it would be drowned out by the sheer volume of the loud music.
What is the difference between a two way mirror and a TV mirror?
The difference between the two is very small. A TV mirror is designed specifically to allow more light through, making it more transparent and less opaque than your typical two way mirror. This aids in security without hampering viewability.
What is the difference between a one way mirror and a two way mirror?
These two terms actually mean the same thing. A "one way" mirror, technically, is just a normal, everyday mirror. Many people will say "one way" mirror when they are talking about a "two way" mirror. A one way mirror only reflects light one way--right back at you. A two way mirror, on the other hand, is a mirror that you can see through, depending on the right circumstances. In other words, when light hits the surface of a two way mirror it reflects back at you while simultaneously reaching the observer on the other side.
How fast can I get the mirror?
If you live in the United States, we can ship it overnight via FedEx or USPS. Your shipping options will appear after you add items to your shopping cart and check out. International deliveries are shipped via USPS Global Priority Mail or USPS First Class and usually arrive in about 4-9 business days. International Express Mail usually takes about 2-4 days.
What glue should I use with acrylic?
For a permanent bond, we recommend epoxy simply because most other glues don't provide the sort of long-term bond you need. The tan-colored opaque epoxy we sell on our main product page works great. Whatever you do, don't permanently glue the mirrors to anything of value. Instead, frame the mirror and then mount the frame around or next to the valuable object. If you are going to glue the mirror directly to an object, make sure that you only glue behind covered areas or around the edges. This is very important, as under some lighting conditions the glue will show through the semi-transparent mirror. Therefore, we highly recommend that you purchase a sample piece from us to practice on before using glue on your full-size mirror.
Which is better, glass or acrylic?
In general, acrylic is the best material to use for two way mirrors because it is more durable. It is easier to scratch than glass, but it doesn't shatter. It is also a lot easier to cut than glass, and the edges aren't nearly as sharp. We don't sell glass mirrors because of the fact that glass and acrylic two way mirrors look exactly the same, but acrylic is stronger and less expensive. In fact, in some situations you don't want to use glass because of it's potential to shatter, i.e., situations in which people may break through the glass and/or cut themselves. Another factor to consider is that while acrylic can be protected against scratching by coating it with Novus 1 cleaner, glass mirrors are just as scratch-prone on the coated side as acrylics.
How strong are your mirrors?
Our 1/4" thick acrylic mirrors can easily withstand a high-speed impact from a blunt object. In fact, we've tried to break them with hammers and found that the most damage we could do was break off some small chips. Chances are, our mirrors are tougher than you'll ever need them to be.
What's the largest size you can cut?
The full sheet size is 48"x96". Full sheets are quite floppy, so we recommend the following maximum sizes:
1/8" thick acrylic: 24"x24"
1/4" thick acrylic: 36"x48"
What are the technical specifications of the material?

Disclaimer: Our data is based on information we believe to be reliable. It is offered in good faith, but without guarantee, because conditions and methods of use are beyond our control. We recommend that our customers determine the suitability of our materials before using them in situations involving risk.
Is it possible that the mirror will break in the mail?
It's very unlikely that our mirrors will break in transit. Our mirrors are packaged in custom boxes and wrapped in strong, flexible packing materials to ensure that they're well-protected during transit. Our large mirrors are also insured against breakage.
Do you offer combined shipping discounts?
Of course! Shipping prices are automatically computed when you use our online shopping cart and you get even more discounts if you buy 5 or more of the same size of mirror. See our wholesale discount page for our quantity discounts.
Is there any difference in quality between 1/8" and 1/4" acrylic?
In general, the 1/4" acrylic is much better for security purposes, because it's increased thickness gives it a lot more rigidity. It is also better to use the 1/4" acrylic in situations in which someone might break it or fall through it, such as in an interrogation or observation room. The 1/4" acrylic also is much better for mirrors above 24"x24", because the 1/8" acrylic tends to get quite floppy and unmanageable in the larger sizes.
What is the best tool to use to cut the mirrors?
For large mirrors, the best thing to use is a table saw with a fine-toothed, no-melt blade. For smaller mirros, use a scroll or band saw. If you are on a tight budget, a Dremel tool with a woodworking circular saw attachment works nearly as well. Jigsaws also work, though not as well as the aforementioned tools due to the fact that you need to hold it down firmly in order to keep it in place as you cut. When properly used, a router can do the trick as well. It's very importants that you do not remove the protective lamination from the mirror before cutting it. Also, make sure that you wear the appropriate protective gear, such as goggles, when working with our products and do not operate a saw without the blade guard. For further information, please see our guide on how to cut our mirrors.
After cutting, remove lamination from both sides.
Can the mirrors be used outside?
Yes, you can use our mirrors outside, but make sure you seal the edges with silicon sealant to keep out moisture and protect the mirror coating. In order to prolong the life of the mirror, make sure that it is protected from the elements. The mirror may get scratched if used outdoors, so you may want to install the mirror in a way that it can be easily replaced in the future. A great way to protect your mirror is by placing a clear piece of acrylic or glass over it. The coated side will be sensitive to water, so make sure that the non-coated side is the side that faces outdoors. Our mirrors can be custom cut to replace existing panes of glass, but make to note if you need 1/8" or 1/4" thickness before ordering.
What should I use to clean the surface of the mirror?
For loose debris and dust, you can use compressed (canned) air like you use to clean your computer's keyboard and ports. For smudges, fingerprints, and stains, use Novus spray and cleaning wipes, which are specifically made to clean acrylic.
Use canned air to remove dust
How should I use the sample you send me if it's not big enough?
The easiest way to test the lighting with just a small piece is to cut a hole in a large piece of cardboard and place the sample over the hole. This will allow you to gauge your next move.
How can I buy a framed mirror of a different size?
Currently, we only sell standard picture frame sizes, but you can easily get a custom frame made at a local frame store. Make sure that you buy the mirror first so that the frame can be made to fit perfectly.
How can I make my own two way mirror?
We don't provide directions telling people how to make their own two way mirrors because it involves handling extremely hazardous chemicals and we don't want anyone to get hurt attempting to do so. It's easier, less dangerous, and less expensive to buy one from us pre-made.
How can I set up a camera to record while I'm away at work or on vacation?
There are a few different ways to set up a home security system. If you're using a single camera, the best way is to buy an inexpensive SVIDEO / RCA / TV input card (such as the kworld brand) for your computer from newegg.com . You can then use the TV viewing software that comes with it, or download software at download.com . We recommend Active WebCam, which is affordable, reliable, and quick to set up. The best thing about using your computer to record video is that you can view what's going on from any computer via the Internet. To see our live demo, please click here.
For a multi-camera setup, you can use a motion-activated DVR (digital video recorder). We sell them at http://www.hiddencamstore.com .
Does it matter which side is facing outwards?
In most situations, the uncoated side should be closer to those being observed. If you are using a camcorder, it should be closer to the coated side, unless you are dealing with a teleprompter application.
How do I figure out which side is the coated side?
The easiest way to figure this out is to put your fingernail against the mirror. If there is a gap between your finger and its reflection (i.e., you can see the entire tip of your finger in the mirror), it is the uncoated side. If there is no gap between your finger and its reflection, it is the coated side.
COATED SIDE - no gap between finger and reflection

UNCOATED SIDE - gap between finger and reflection
What is the best way to clean the mirror?
When cleaning your new mirror, you have to be careful - acrylic scratches fairly easily! To clean dust off your mirror, use compressed air (such as a computer duster) to avoid streaking. To get rid of fingerprints, the best product to use is Novus 1 cleaner and Novus Polish Mates, which you can order on our website. Novus 1 can get rid of scratches and light scuffs and also adds a protective coating to prevent further damage. Do not use water, Windex, or other corrosive agents on your mirror. You also don't want to use Novus on the coated side unless you have to clean off some sort of oily residue.
What is the appropriate way to handle and care for the mirror?
One thing to avoid is storing your mirror at an angle, as the acrylic will bend over time. The uncoated side of the mirror isn't susceptible to water damage, but the coated side is - so avoid leaving the coated side exposed to high humidity or outdoor conditions which may result in it getting wet. The coated side of the mirror has a protective transparent coating on it which protects against scratching. You want to avoid cleaning the coated side as much as possible, as scuff marks may be left behind and the cleaning solution may leave residue. You can clean the uncoated side repeatedly, as long as you are using a cleaner such as Novus 1 and Polish Mates.
Clean using Novus 1 & Polish Mates
Do you have any tips for using them with camcorders?
At the factory, the mirror coating is applied on the clear acrylic, followed by a clear finish sprayed over the aluminized coating, forming a lattice structure. Even though this lattice structure is extremely tiny and invisible to the naked eye, a good camera on auto focus may try to focus on it. When this happens, the resulting picture is similar to looking through a screen-door. To avoid this, position the camera as close as you can to the mirror (1-2" away at the most, but not directly against it) so that the auto focus will focus on what is behind the mirror rather than on the mirror itself.
How much light is transmitted through the mirror?
Our two way mirrors allow about 15% of the light through, our TV mirrors allow about 25-65% to get through, and our teleprompter mirrors allow about 40-65% through. Please see the respective product pages for more details.
How much do the mirrors weigh?
1/8" Thick - 11.3 oz per sq foot (320g)
1/4" Thick - 22.6 oz per sq foot (640g)
What chemicals have an effect on the mirrors?
Like all plastic materials, mirrored acrylic will react when exposed to certain chemicals. Below is a partial list of chemicals known to react with acrylic mirrors; exposure to them should be avoided. External factors such as fabrication stresses, exposure to loads or changing temperatures, and the method of application can influence the possible reaction as well. Care should be taken with dry chemicals or solvents used near the mirrored acrylic at all times.
KNOWN CHEMICALS THAT ATTACK MIRRORED ACRYLIC:
BENZENE ETHYL ALCOHOL
LACQUER THINNERS KETONES
ESTERS METHYL ALCOHOL
CARBON TETRACHLORIDE ETHERS
TOLUENE
What is the "fingernail test" urban legend?
An e-mail hoax circulating around the Internet reads that people should be careful at department stores, because many of them have two way mirrors installed in their restrooms and changing rooms to deter theft (a feature which is obviously ripe for abuse). If you put your fingernail up against the mirror as described above and there's no gap between your fingernail and the mirror, the email states that you are dealing with a two way mirror. This e-mail is obviously wrong, because a properly installed two way mirror has the non-coated side closer to the viewed subject. Therefore, it will appear exactly like a regular mirror when you put your fingernail against it. The best way to detect a two way mirror is with a laser pointer or a good flashlight. If you hold the laser pointer or flashlight against the surface of the mirror, you will faintly see the beam on the other side if it is a two way mirror.