What You Must Know About Laminating and Laminating Films

Photo Courtesy of Avery Dennison

 By Jim Hingst 
@hingst_jim

Laminating films can beautify and protect graphics. Selecting the right overlaminate for the application, however, does not guarantee a beautifully finished project. There’s much more to successful laminating. To ensure the best results I have compiled some tips and tricks about laminating films and operating a laminator.  

1.       Do not stack the rolls of unboxed laminating film horizontally, one box on top of another. If the roll lies against a side of the box, you can create a flat spot in the roll. This can appear in the laminated print as a visible line.

2.       Keep rolls of overlaminates in their boxes, stacked upright, until you need them. Although the corrugated boxes used for overlaminates are designed to protect the rigors of shipping, stacking these boxes horizontally can result in their collapse, when weight becomes excessive.  

3. The best storage environment for laminating film is a temperature and humidity controlled room, at 70°F at 50% relative humidity. Under these conditions, the expected shelf life of overlaminates typically is +1 years. 

4.       The best environment for applying overlaminates is a clean shop. In cleaning your machinery, never use an air hose. Much of the blown off dirt goes airborne and eventually settles on your raw materials. Dirt trapped between the print and the laminating film usually results in tenting of the laminating film over the trapped particle. To clean the rollers of your laminator, try using a tack cloth.

5.       Before applying an overlaminating film to your print, be sure the ink on the print is completely dry.  Two good rules of thumb are to wait 72 hours before laminating the print, so the inks can cure properly; and before mounting or rolling up the laminated print, let it lay flat for 24 hours. 

Even if the print feels dry to the touch, its ink may not be completely cured.  The time it takes for a print to dry varies depending on the density of the ink on the print, ambient temperature and the humidity in your shop. Usually, inks take longer to dry, when temperatures are cooler and the humidity is high. Consult the manufacturer’s recommendations on drying time.

6.       The interaction of inks, printing systems and print media  involves very complex chemistry. Incompatibiltiy among components can adversely affect  the abiilty of the overlaminate to adhere to the print and result in delamination.  Always test and evaluate your raw materials (laminating film, print media, and mounting substrate) before a production run. When you find a winning combination, stick with it. 

Rule of Thumb: In selecting a laminating film for vinyl graphics, the general rule is: use a cast vinyl overlaminate for cast vinyl graphics; use either a calendered or cast overlaminate for calendered vinyl graphics. 

7.       Applying a laminating film to a print should be done in one continuous pass. Whatever you do, don’t stop in the middle of a print to see how it’s going. You’ll only end up with a flat spot in the adhesive, which can result in streaks and air pockets. 

8.       Proper unwind tension on the supply roll of the laminator is critical in achieving satisfactory laminating results. As a general rule, a little is better than a lot. Use the least amount of tension as needed to get the job done.

9.       High unwind tension stretches the laminating film. Any stretched film, especially a stiff film, such as a polyester, has a memory and tends to return back to its original shape. This can cause the laminating film to either curl or delaminate from the print. Excessive tension can also result in delamination of the print from the substrate to which it is mounted.  

10.     Pressure sensitive laminating films need pressure so the adhesive on the film properly flows out and makes complete contact with the surface of the print.  Inadequate adhesive wetting can result in tiny bubbles of air being trapped between the laminating film and the print or producing a cloudy appearance. The amount of pressure needed in applying a laminating film can vary from film to film.  Overlaminates generally require between 40 and 100 psi of laminator pressure. If air bubbles appear, possible solutions include increasing the nip pressure; slowing the laminating speed, and, if worse comes to worse, using a little heat.

11.     Take your time in laminating. To reduce air bubbles, keep laminator speed at less than 5 feet per minute.

12.     Opinions vary on the use of heat in applying pressure sensitive overlaminates. Do pressure sensitive overlaminates need heat to bond to the print? Of course not! Pressure sensitive films need pressure to bond. But using a little heat can help.  Some people argue that, with little heat on the top laminator roller (from 80°F to 120°F), the adhesive on the laminating film flows out better, which creates a better bond to the print. The opposing argument is that heat can cause the laminating film to shrink, resulting in delamination from the print.  The safest bet is not to use heat, unless you have a problem. 

Starts-and-stops in the lamination process can show up as lines in the adhesive and over the print to which it is applied. Remove release liner in one continuous pass. 

13.     Set up your laminator to remove the liner just above the nip of the rollers.  Doing this helps keep the adhesive free of dust.

14.     Humidity in your customer’s shop can affect their finishing job.  High levels of humidity can prolong the time it takes for a print to dry.  Laminating a print before it is thoroughly cured can result in solvents and moisture being trapped between the media and the laminating film. 

To minimize problems caused by high humidity, shops should maintain the humidity within their shops between 20% and 50%. Before laminating, allow enough time for the print to dry.  To aid drying, direct fans on printed graphics.  After laminating, let prints lie flat for 24 hours before rolling to allow the adhesive system of the laminating film to wet out on the surface of the print.

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About Jim Hingst: After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.

Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer.  Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.

Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for  publications, such as  Signs Canada, SignCraft,  Signs of the Times, Screen Printing, Sign and Digital Graphics and  Sign Builder Illustrated. He also posted more than 325 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published.  Vinyl Sign Techniques is available at sign supply distributors and at Amazon. 

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© 2016 Jim Hingst