Two Way Mirror FAQ

Two Way Mirror FAQ

How does a two way mirror work?
A two way mirror is a semi-transparent film of aluminum deposited on an acrylic substrate. The allows a percentage of the light to pass though while reflecting the remainder.

Everyone has seen a television show or movie in which a criminal suspect is questioned while detectives watch from behind a one-way mirror. Why doesn't the "criminal suspect" see the detectives in the next room? The answer lies in the lighting of the two rooms. The room in which the glass looks like a mirror is kept very brightly lit, so that there is plenty of light to reflect back from the mirror's surface. The other room, in which the glass looks like a window, is kept dark, so there is very little light to transmit through the glass. On the criminal's side, the criminal sees his own reflection. On the detectives' side, the large amount of light coming from the criminal's side is what they see. In many ways, it's the same as if people were whispering in one room while a loud stereo played in the other. The sound of the whisper might carry into the room with the stereo, but it would be drowned out by the intensity of the music.

If the lights in the room with the mirror are suddenly turned out, or the lights in the observation room suddenly turned on, then the one-way mirror becomes a window, with people in each room able to see those in the other. You can see this effect in any mirrored office building at night -- if the light is on in an office, you can see into the office just fine.
What is the difference between a two way mirror and a TV mirror?
They are similar: the TV mirror is specially designed to allow more light to pass through. In other words, it's more transparent and less opaque than a standard two way mirror, which is intended for security, not viewability.
What is the difference between a one way mirror and a two way mirror?
They are two different terms for the same thing. A "one way" mirror is technically just a regular mirror. Many people often use the term when they really mean "two way" mirror. A one way mirror only reflects light one way--back at the viewer. A two way mirror is a mirror you can see through. In other words, light strikes the surface and goes two ways: back at you and towards 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 USPS or FedEx. Your shipping options 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 arrive in about 4-9 business days. International Express Mail takes 2-4 days.
What glue should I use with acrylic?
We recommend epoxy for a permanent bond. From our experiences, many other glues don't provide a good long-term bond. We sell tan colored opaque epoxy on our main product page. Do not permanently glue the mirrors to anything of value. Instead, frame them and then mount the frame around or next to the object. If you are gluing the mirror directly to an object, be sure and only glue around the edges or in back of covered areas. Glue can show through the semi transparent mirror under some lighting conditions. We recommend that you buy a sample piece from us to practice on before gluing your more expensive mirror.
Which is better, glass or acrylic?
Generally, acrylic is the better material for two way mirrors. Acrylic is more forgiving material. It doesn't shatter, but can be scratched more easily than glass. It's also easy to cut, and the edges aren't dangerously sharp. Acrylic and glass two way mirrors look the same, but the acrylic is less expensive and stronger, which is why we don't sell glass mirrors. For some situations, glass is not up to code because of it's potential to shatter--glass is not appropriate for situations where people may cut themselves or break through the glass. Keep in mind that glass is equally scratch-prone on the coated side, and that acrylic can be protected against scratches by coating it with Novus 1 cleaner.
How strong are your mirrors?
Our 1/4" thick acrylic mirrors are easily able to withstand high velocity impacts from blunt objects. We have tried to shatter them with hammers and found that the most damage we could do was break off small chips.
What's the largest size you can cut?
The full sheet size is 48"x96". It is quite floppy in that size, so the maximum recommended sizes are:
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 uncommon for our mirrors to break in the mail. They are packaged with a custom boxes and strong, flexible packaging materials to ensure that they are well-protected. Large mirrors are insured against breakage.
Do you offer combined shipping discounts?
Yes, they are automatically computed when you use our online shopping cart. Further discounts are available if you plan to buy 5 or more of the same size of mirror. Please see our wholesale discount page for our quantity discounts.
Is there any difference in quality between 1/8" and 1/4" acrylic?
Generally the 1/4" acrylic is better for security purposes, because it's a lot more rigid. The 1/4" is also useful in situations where a person might break or fall through it, such as on a wall, or in an observation or interrogation room. 1/4" is much better for mirrors above 24"x24", because the 1/8" gets quite floppy in larger sizes.
What is the best tool to use to cut the mirrors?
For large pieces, the best tool is a table saw with a fine-toothed, no-melt blade. For smaller pieces, use a band or scroll saw. If you are on a budget, a Dremel tool with the optional woodworking circular saw attachment works. Jigsaws also work, though less well because you need to hold it down hard to keep it in place. Routers, when properly used, can cut our mirrors as well. Do not remove the protective lamination from the mirror before cutting it. Please wear appropriate protective gear, such as goggles when working with our products. Do not operate a saw without the blade guard. For further information, please see our guide on how to cut them.
After cutting, remove lamination from both sides.
Can the mirrors be used outside?
Yes. If used outside, seal the edges with silicon sealant to keep
moisture out and protect the mirror coating. You'll want it to be well-protected from the elements to prolong the life of the mirror. They can be cut to size to replace existing panes of glass (be sure to note if you need 1/8" or 1/4" thickness before ordering). You may want to install it in a way so that it can be replaced at some time in the future, because they scratch easily. Consider placing a regular piece of acrylic or glass over it, to protect the two way mirror. The side facing the outdoors should be the non-coated side, because the coated side is sensitive to water.
What should I use to clean the surface of the mirror?
For dust and lose debris, use canned air (computer duster). For smudges, fingerprints, and stains you can use Novus spray and cleaning wipes, which are specially designed to clean acrylic.
Use canned air to remove dust
How should I use the sample you send me if it's not big enough?
It's often helpful to cut a hole in a large piece of cardboard, and place the sample over the hole. This will allow you to test the lighting with just a small piece.
How can I buy a framed mirror of a different size?
For now, we only sell standard picture frame sizes. However, you can get a custom frame made at a local frame store. Buy the mirror first before having the frame made, so that the frame can be made to fit perfectly.
How can I make my own two way mirror?
We don't provide directions because it involves extremely hazardous chemicals, and we don't want anyone to get hurt trying. It's less dangerous and expensive to buy them already made.
How can I setup a camera to record while I'm away at work or on vacation?
There are a few different ways to setup a home security system. The best way when using only one camera 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 program that comes with it, or download a program off download.com. We recommend a program called Active WebCam, which is inexpensive, reliable, and fast to setup. The biggest advantage of using your PC to record video is that you can view what's going on from 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 installations, the uncoated side is closer to the people being observed. If you are using a camcorder, it should go closer to the coated side (the exception being teleprompter applications).
How do I figure out which side is the coated side?
Hold an object such as your fingernail against the mirror. If there is a gap between the object and its reflection, it is the uncoated side. If there is no gap between the object 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?
Be careful with your new mirror—acrylic scratches fairly easily! Cleaning of dust should be done with compressed air (computer duster) to avoid leaving streaks. To clean oil or fingerprints, use Novus 1 cleaner and Novus Polish Mates. Novus 1 can heal light scuffs and scratches, and adds a protective coating to prevent future damage. Please see our website if you are interested in ordering Novus products. Do not use Windex or other corrosive agents on your mirror. Do not soak in water. Do not use Novus on the coated side unless it is necessary to clean oily residue.
What is the appropriate way to handle and care for the mirror?
Do not store mirrors at an angle, or they will bend over time. The coated side is sensitive to water, but the uncoated side isn’t. Avoid leaving the coated side exposed to high humidity or outdoor conditions. The coated side has a protective transparent coating on it which protects it from scratching. Try to avoid having to clean the coated side, because it’s possible the cleaning solution will leave residue and the wipes will leave scuff marks. The uncoated side is fine to clean repeatedly, as long as you are using special plastic cleaner such as Novus 1 and Polish Mates.
Clean using Novus 1 & Polish Mates
Do you have any tips for using them with camcorders?
After the mirror coating is applied on the clear acrylic at the factory, the clear finish is sprayed over the aluminized coating, forming a lattice structure. Even though this lattice structure is small, a good camera with an auto focus may try to focus on it. When this happens, the picture is similar to looking through a screen-door. To avoid this, position the camera as close as you can to the mirror (at most 1-2 inches), but not against the mirror so the auto focus will tune-in on the images coming through the mirror rather then on the mirror itself.
How much light is transmitted through the mirror?
Our two way mirrors transmit about 15% of the light through the material. Our TV mirrors allow about 25-65% to get through. Our teleprompter mirrors allow 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, the mirrored acrylic will react when exposed to many chemicals. Below is a partial list
of chemicals known to react with acrylic mirrors, exposure to them should be avoided. Factors such as fabrication stresses, exposure to loads or changing temperatures and the method of application can all influence the possible reaction. In all cases, care should be taken with dry chemicals or solvents used near the mirrored acrylic.
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 net reads that your girlfriends, wives, etc. should be careful at department stores, because a lot have two way mirrors installed. If there's no gap between your fingernail and the mirror, it's a two way mirror. Obviously this e-mail is untrue, because a properly installed two way mirror has the non-coated side closer to the viewed subject. Thus, it will appear exactly like a regular mirror when you hold your fingernail against it. The best way to detect a two way mirror is with a laser pointer or good flashlight. If you hold the light source against the surface of the mirror, you will faintly see the beam on the other side.

Our Other Companies: Hidden Television - Teleprompter Mirrors - First Surface Mirrors - Mirropane