How to Select the Right Overlaminate

Selecting the right overlaminate for a particular graphics application requires just as must consideration as selecting the right digital print media. And for many, it can be just as confusing, if not more so. For starters, just page through any distributor catalog, and you will find a wide array of options, nearly as extensive as your media choices.

With all that’s available, how do you pick the best one for the job? As self-help guru Anthony Robbins instructs: “If you want better answers, learn to ask better questions.” In selecting the right overlaminate, here is a list of questions for you to consider:

1. What is the application? It's important to pick the right film for the job. Whether the task involves floor graphics, perforated window graphics or fleet markings will dictate the appropriate overlaminate.
2. What substrate will receive the graphics? Will it be smooth, such as flooring, an acrylic or polycarbonate sign face, or will the graphics be applied over rivets or corrugations?
3. What environment will the graphic be subjected to? Will there be temperature extremes, UV light, water or pollution? Will it be subject to acidic or alkaline cleaning agents, or could it be exposed to vandalism, grease or road salts?
4. Under what lighting conditions will the graphic be viewed?
5. What are the job's durability requirements?
6. Is the overlaminating film compatible with other components of the graphics system?

Answers to these questions, will help you select the right overlaminate for your particular application. Before you make a decision, you need a good understanding of the types of overlaminates available. The range of products to choose from includes a variety of facestocks: polyester, polypropylene, polyvinyl fluoride (PVF), polycarbonates, and cast and calendered vinyl. Picking the best overlaminate requires matching product performance characteristics to the application’s demands.

Fleet Graphics. Fleet graphics can take a beating from acidic and caustic chemicals, to the bleaching effects of summer sun, scratches from low hanging branches, and the sandblast effect of dirt and sand as a vehicle rumbles down the road.

These environmental extremes necessitate that you protect all printed vehicle graphics with either a liquid clear coat or an overlaminating film.

In selecting an overlaminate for vinyl fleet graphics, the general rule of thumb is: use a cast vinyl overlaminate for cast vinyl graphics; use either a calendered or cast overlaminate for calendered vinyl graphics.

Screen Printed Fleet Graphics. When choosing an overlaminate for screenprinted fleet applications, test the components before using them in production. Because screen printing deposits an extraordinarily thick layer of ink, these printed graphics typically require an overlaminate with a heavier coating weight of adhesive. An overlaminate with a thin adhesive coating will bridge the edge, causing a slight, but noticeable, air pocket.

Large, laminated graphics should be covered with a heavyweight, low-tack premask. This masking prevents scratches in the overlaminate during installation. It also prevents vinyl graphics from stretching during the application process. Even a laminated graphics can stretch like a piece of warm taffy, when applying graphics in hot weather. If you are installing a fleet graphic, with multiple panels and one panel stretches, you may need to play some games to get the multiple points of alignment to match from one panel to the next.

Transit Markings. Public vehicles, such as buses and train cars, are common targets of marauding vandals armed with cans of spray paint. To protect vinyl graphics from this urban artistry, expensive polyvinyl fluoride (PVF) overlaminate films provide the utmost protection.

Because PVF is a low-energy plastic, paint has difficulty sticking to it. These films, which also provide excellent UV and abrasion resistance, are ideal for graffiti-proof markings, but because these films don’t stretch, they can be used only for flat applications.

PVF’s anti-graffiti properties don’t last forever. If solvents are used to clean vandalized graphics, the cleaning chemicals can etch the surface. The result is that the next time the graphic is spray painted, complete removal of the graffiti may not be possible. As an alternative to solvents, try cleaning tagged graphics with a nylon-bristle brush and citrus-based cleaner, such as Simple Green®.

Perforated Window Graphics. Some vinyl companies recommend or require an overlaminate with their perforated window-graphics film. This precludes using application fluid, because fluid would be trapped inside each little hole.

So why use an overlaminate at all? Failure to use an overlaminate on perforated window graphics films, can result in problems. An overlaminate protects the printed image from the degrading UV rays of the sun, thereby increasing the useful life of the graphic. Without an overlaminate, dirt can collect in the holes, which can cause the edges to lift. An overlaminate also prevents the film’s holes from filling with water, when it rains, obscuring vision through the graphic in a storm.

For store windows or other flat applications, you can use a polyester overlaminate. Curved surfaces, however, require the use of a cast vinyl overlaminating film. Following graphics application, you should coat the edges of the graphic with a commercial edge sealer.

Tankers and Cement-Trucks. Clear coating provide great short-term protection for signage and promotional pieces, but they don’t outperform overlaminates for demanding applications. Graphics on chemical tankers are frequently subjected to chemical spillage. Acids, caustics and solvents can quickly erode the ink and clear coat system of printed fleet markings, as well as leech the plasticizer from pigmented vinyl, embrittling it and causing the film to crack. Cement-truck graphics, which are easily damaged by caustic cement and harsh cleaning chemicals, should also be overlaminate-protected.

Although vinyl overlaminates are usually best for vinyl markings, chemical tankers and cement trucks are an exception. For protecting markings subject to chemical damage, a polyester overlaminating film was the best choice 30 years ago, and remains so today.

Shortcomings of Polyester Overlaminates. While polyester overlaminates exhibit outstanding chemical and temperature resistance — features that also make it an excellent protective film for warning labels. But, because polyester isn’t conformable, it can’t be used over rivets, corrugation or compound curves.

Graphics laminated with polyester require special handling. To prevent tunneling, delamination or bubbles between the overlaminate and base film, graphics are best stored and shipped flat. During installation, take special care to avoid delamination.

Furthermore, to prevent edge lifting, graphics applied to the surfaces of tankers that haul caustic or petroleum-based products should be coated with a commercial edge sealer.

Floor Graphics. Because floor graphics must withstand extraordinary abuse from pounding foot traffic, dirt, grease, grit and chemical cleaners, overlaminates are the best choice for these demanding applications. Not only can this tough, resilient film withstand heavy daily traffic, its matte texture prevents slippage.  

To ensure that a floor graphic is slip-resistant, overlaminates are rigorously tested. One industry standard is American Standard for Testing Materials (ASTM) D2047.

This ASTM test checks the overlaminates’s coefficient of friction, the force required to move one material over another. In essence, the test measures the traction a pedestrian could expect as he or she walks on a floor graphic.

In-Store, P.O.P. and Exhibits. As digital printing has grown in the sign industry, so has the use of overlaminates for signage, interior-wall and tradeshow graphics, and P.O.P. applications.

Thick polycarbonate overlaminates are also often used for the protection of exhibit materials. These rigid films are available in a variety of thickness.

In engineering tradeshow graphics, a good practice is to select materials (media, backer and overlaminate), which when laminated together will provide a construction, which is at least 20 mils thick.

Polycarbonate overlaminates are well suited for exhibit and display graphics because they provide excellent lay-flat characteristics, and their velvety texture eliminates any glare from overhead lighting. Polycarbonate can also withstand the rough handling encountered when rolling and unrolling tradeshow graphics.

In selecting the right overlaminate for a job, the most important consideration is the application. To keep your customer happy, also make sure that you understand your customer’s expectations and any special requirements of the job. To get the answers you need, ask questions – plenty of them.

For more information about overlaminates and vinyl graphics, refer to my book, Vinyl Sign Techniques and the Graphic Installers Handbook by Rob Ivers.