In the realm of reflective sheeting, the term metallize means to apply a mirror backing. Specifically, to the bottom of a glass bead or to the back of a prism. This is done to increase its return of light and the overall retro reflectivity of a tape. When you look at a mirror every morning, you are seeing a metallized backing on a sheet of glass. In fact, the only difference between a sheet of smooth glass and a mirror is the metallized coating.
Engineer Grade glass bead films, being the first reflective sheeting invented, are always metallized films, meaning the beads sit in a layer of thin aluminum which acts as a mirror finish. If you peel the release liner from engineer grade, you can see the silver finish. This enhances their ability to reflect light. On top of the beads is a layer of colored or clear polymer. All of these layers are fused together to form one layer that will not delaminate. It is because of this that you can cut engineer grade with an exacto, scissors, or a plotter, without having to worry about intrusion from the elements. Engineer grade is also an enclosed film which simply means the beads or reflective elements are completely covered by a protective polymer.
When it comes to brighter prismatic films, they come in two varieties, metallized and non metallized (air backed).
Reflective films like a Nikkalite High Intensity Micro Prismatic, or an Oralite 5900 Type 4 are air backed films. This means that a colored prism array in the form of a sheet, sits on top of a white backing or sheet. Between these two films is a layer of air. This setup provides for excellent reflectivity and color vividness without the need for a mirror backing. The main drawback of this design is durability in rugged environments. Since the two layers are sandwiched together, they can separate, especially when impacted. Air backed films are simpler and less expensive to make, so they are more cost effective for applications like signs. So in summary, air back non metallized films perform well where they will not be abused or impacted. They are not as rugged as enclosed lens metallized films. (One exception to this rule is Oralites 5934 reboundable series of prismatic tapes. They feature a very rugged top coat which provides quite a bit of protection for the prism array.)
Metallized films are more complicated to produce, and generally cost a little more. But they are rugged. The original films made by Oralite (formerly Reflexite) were and are metallized, bonded into one layer, nice and thin, and patented. Because they are one layer, they can be CAD cut into letters, shapes, etc.. Also, when they are cut, it is not necessary to seal the edges since there are no layers for water to seep between, or to delaminate and come apart. This makes them rugged and gives them their ability to take a beating and not only stay in one piece, but continue to reflect as well. This continues to be a big feature of Oralite (formerly Reflexite) films. You can literally beat them with a hammer and they will still reflect and stay together. So the bottom line is, for applications in dynamic rugged environments, choose a single layer metallized retro reflective tape.
Soon after Oralite came out with prismatic reflective tape, other companies began making prismatic films in a different way, without the mirror backing. These films were called non metallized or air backed prismatic. Films designed this way were less expensive to manufacture, and could be sold at lower prices. It was found that a micro-prism, if sitting on a layer of air, backed by a layer of white, would reflect just about as well as a metallized prism. So these other companies began producing air backed films, mainly for signs. The new films worked well for signs since that application was static and not dynamic. In other words, the films would not be treated roughly while on a sign post 6 plus feet in the air. Air backed films are also nice and vivid in the day, and plenty bright at night. This is because there is no silver colored backing altering the colors. So a yellow stays nice and vivid. The same yellow in a metallized film would lean more towards an amber color. The reflected color would be the same, but the daytime color would be a little different. (see photo above for comparison)
Below is a list of differences between Metallized and Non Metallized films.
– Metallized films are fused into a single layer and do not delaminate. Non Metallized films consist of two main laters and can delaminate, especially in rough conditions.
– Metallized films are thin and low profile. Non Metallized films are about twice as thick. (higher surface profile)
– Metallized films are thin, so they bend easily and wrap around smaller diameter tubes. Non Metallized films are stiffer like a credit card and do not wrap well around small diameters. You can wrap a V82 metallized film around your finger, but you could not do this with a 3m Diamond Grade film.
– Metallized films like Oralite V98, V92, V82 can be CAD cut by a plotter. Non Metallized films are difficult to CAD cut due to how thick they are and how hard the surface is to cut into. Also, the two layers create cutting difficulty.
– Because of the silver backing, metallized films are not as vivid for WHITE, YELLOW, and ORANGE. Non Metallized (air backed) films are more vivid and more visible in daylight. Both are about the same reflecting at night.
– Metallized films do not require edge sealing when cut since they are bonded into one layer. Non Metallized films should be edge sealed to protect exposed edges. Otherwise water and weather can seep in between the layers. Not sealing allows the edges to become a little cloudy, but no more than 1/8″ around the perimeter.
*Note – to be clear, the layers in a metallized reflective tape are fused together in the manufacturing process so that they do not separate. So there are layers, however, they are welded together to create a single layer. If you look at the picture below, the air space layer with the little bridges on the non metallized film (bottom of picture) is where delamination would occur.
In closing, metallized and non metallized films both have a valuable purpose in the vast industry of traffic and personal safety. One is not necessarily better than the other, however, for different applications, each have their advantages. I normally explain it as metallized films are great for vehicle graphics and dynamic (rugged) applications like DOT trucks, and non metallized films are excellent for signs (static applications).
Steven Cole (Economics, MBA – University of West Florida , Business & Innovation – Stanford University) 25 years of experience in the reflective safety business. Specializing in vehicle accident and rear end collision reduction through increased visibility.