."The Basics of Film Laminating"
[Column #64, 4/00]
Some finishing services are tried and true. They seem to have been around forever, people on the street rarely notice them, and we take their usefulness for granted. Film laminating is one of those services.
Nothing beats this method of protection in terms of durability, high gloss, scuff resistance, and prevention from cracking. That is why it is found just about everywhere: menus, cards, placemats, pocket calendars, outdoor posters, book covers, dust jackets, video slipcovers, cassettes, index tabs, maps, and packaging. Other popular applications for film laminating are write-on/wipe-off wall posters, presentation folders, binders, brochures, and casebound products.
Laminating is a fairly simple process that involves bonding a thin, transparent film—typically polypropylene, polyester, or nylon—to the surface of the press sheet or other substrate. The film can be applied in two ways, via the wet method or the thermal method. The wet method is the more complicated of the two and involves the use of solvents or water. The finisher applies the adhesive to the film as the film is being applied to the substrate. This method tends to be less expensive than thermal but there may be environmental problems during the glue-drying process. The thermal method, which has become popular in the past few years, uses 200- to 300-degree heat to meld film and substrate. The film used in thermal laminating is precoated with polyethylene adhesive and, therefore, is more costly than film without adhesive. Thermal adhesion is by far the most popular method for film laminating so I’ll focus on this process.
The biggest drawback of thermal adhesion is the potential curling that can occur in the finished piece. When heat is used on polyester and especially on polypropylene, the film stretches during the application process. After it is applied and cooled, shrinkage occurs causing curling. (Go in to any bookstore and you’ll find the covers curling away from the book.) To avoid this problem, specify layflat nylon film (also known as curl-free film). Nylon film is generally more expensive than other types of film, but it is the most stable and comes in a variety of finishes to suit the customers’ needs.
The most popular film for the laminating process is polypropylene. It is available in a gloss, satin (providing excellent color consistency), and delustered or matte (providing great readability) finish, is a bit softer than other films which means it folds easily but is more prone to scratching, and is the least expensive. Polyester film, which also comes in gloss, satin, and delustered, has a harder finish and is more resistant to scuffing and tearing than polypropylene.
All laminating films are classified by thickness, which is measured in mils (increments of 1/1,000 of an inch). The thinnest film available, about 1.2 mils, works well for products that will be rolled or folded, such as menus, maps, book covers, and book jackets. Heavier films, ranging from 3 to 10 mils, are often used for menus, credit and ID cards, and posters.
Care must be taken in selecting the appropriate weight for a given job—coating a brochure in 10-mil film, for example, would make it nearly impossible to fold. A good medium-weight film is 5 mil; it’s half the price and still provides a stiff, substantial finish. In cases where a very stiff, heavy-duty coating is desired, combining 5-mil film with a heavier paper stock yields results identical to 10-mil lamination at a significantly lower price. Usually, heavier films (5 mils and up) are applied to both sides of the substrate, while lighter films are sometimes applied to only one side. Laminating both sides of a substrate can be considerably more expensive both in material and time costs. In addition, films above 3 mils are often extended over the substrate’s edge to create a waterproofing seal (referred to as encapsulation).
There are many options in the film laminating process. Discuss them with your finisher during the planning stages of your job.
Films will adhere to virtually any paper or card stock, as well as cardboard and cloth. Heavy paper stocks are better than lightweight, which tend to curl when laminated. Occasionally, films will have trouble sticking to uncoated or heavily textured stocks, because it is difficult for the film to get down into the valleys of the paper. If you are concerned about the compatibility of your stock and your film, have your finisher do a test run.
As with most coatings, lamination yields the best results when used over wax-free inks and varnishes. If some wax is present in your ink or varnish, ask your finisher to run a test sheet. They may recommend the wet method of lamination, which allows the use of very aggressive adhesives to effectively bond the film to the substrate.
Determining whether to use film laminating or varnishes or coatings depends on the end-use, cost, and other finishing processes involved in the job. Since lamination is the ultimate in terms of gloss and structural strength, it is an excellent choice for products that must withstand heavy usage. On the other hand, film lamination is not economical for products with a short shelf-life, such as brochures or menus that require frequent price changes. The price of lamination varies depending on the type of film used; however, it usually costs about twice as much as UV coating.
Laminating can be done in conjunction with die cutting, scoring, embossing, and debossing, but these processes should be performed after the film is applied to the substrate. If the product is embossed before lamination, the bump-up (height) of the embossed area will be flattened by the rollers that apply the film. If the job involves deep embossing, choose a soft film, such as polypropylene, that has greater elasticity than other types. As always, run a test first to make sure your film won’t crack under the pressure of embossing.
Foil stamping on films is a tricky business. We highly recommend foil stamping be done before lamination to minimize adhesion problems. One alternative, however, is to use a stampable polyester film, which is treated to accept foil more readily than untreated films.
For projects that will be glued, such as presentation folders, bags, and box wraps, specify a glueable film. The cosmetic packaging, toiletry, and pharmaceutical industries usually insist on glueable films.
Finally, because of the way film is applied, there is no such thing as spot lamination. If you don’t want to cover the whole sheet, spot-coat a varnish or UV coating. Another option would be to film laminate with a matte film and spot-UV coat on top of it—it has a great effect!