If you research the term “lamination” online, in print books, or by talking with commercial printers, you’ll see that the concept has two distinct meanings.
The first and more common refers to the addition of a plastic protective sheet to the surface of a custom printing job, whether it be a book cover or a large-format print.
The second and less common definition describes an item composed of multiple parts glued together, such as “double-thick cover stock.” It can also be used to reference an undesirable coming apart of composite items, such as when the surface of a custom printing paper stock delaminates.
Protective Lamination
Let’s start with the first definition. If you wish to protect a large-format print from moisture, fingerprint oil, and such, you would coat the sheet with film laminate. You could cover one side of the poster printing run with film, or you could even cover both the back and front with separate sheets, effectively sealing the custom printing paper completely into a plastic pouch of sorts. This is what is done with some restaurant menus and placemats, since they receive rough treatment and endure multiple spills.
Print book covers are treated in much the same way. Either a film laminate can be laid over and adhered to the substrate, or a liquid laminate can be used to coat the sheet, using a metal blade to distribute the thick, protective fluid.
Unfortunately, when only one side of a press sheet is coated, as with a perfect-bound book cover, moisture can enter the uncoated side of the paper surface and cause the sheet to curl. A unique coating exists called “lay flat laminate,” which has microscopic grooves that allow the coating to expand and contract to prevent curling. These coatings can also be made of a porous material such as nylon, which is permeable by water and air, and which allows the outside covers and inside covers to maintain an equilibrium, thus avoiding curling.
Lamination Defined as the Adhering of Component Parts (Such as Different Papers)
Picture the recurved wood bows of prior decades, which were composed of wood and fiberglass glued together (laminated) into a strong and flexible hunting weapon able to deliver arrows with precision. This is the idea behind laminated paper.
For instance, you might choose a double-thick paper stock for a high-end promotional project. One side of the sheet may be an uncoated green tinted cover sheet, while the other half of the thick paper might be a white cover stock. Both are glued together flawlessly to give a bit of interest to the cover material and at the same time to create a strong paper substrate.
Another use for lamination is to glue a coated press sheet printed via offset lithography onto a coarser grade of paper. For instance, the graphic panels of a movie theater “standee” are coated press sheets glued to corrugated board. The corrugated board gives the structure lightness and rigidity, while the offset coated sheet provides a gloss coated surface that can go through the heat and pressure of an offset press (unlike the corrugated board itself). In fact, the custom printing vendor might also add a transparent lamination (gloss, dull, or silk) over the gloss offset press sheet. This film might then protect the ink on the paper surface from the oily fingers of moviegoers while also adding dimensional strength to the finished and assembled “standee.”
On the undesirable end of the spectrum, if the ink on press had too high a tack, the surface tension of the ink could pull apart the surface of the paper running through the press. This is called delamination. The fibers compressed by the Fourdriner machine into the press sheet during the papermaking process can come apart if the tacky ink (acting like glue in this case) pulls apart the paper.
This entry was posted
on Thursday, January 12th, 2012 at 7:15 pm and is filed under Digital Printing, Large-Format Printing, Paper and finishing, Poster Printing, Soft Cover Book Printing.
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