Investigating the Technology Behind ‘Crack-free’ Paperboard
A lot of great things arrive at my doorstep these days. A few weeks ago, I got a great sample package from Iggesund Paperboard regarding their Invercote line of premium paperboard. They sent me some really gorgeous packaging samples — you know, the kind you’d want to save because they are too cool to throw away — and a note that said their paperboard will not crack at the fold with or against the grain, on even their heaviest 144-lb cover.
Well, that’s a pretty hefty claim, so I had to investigate. Obviously, there must be some technology behind this paperboard, and since this is a finishing technology blog, I think it’s fair game.
I contacted Neal Haussel, sales manager, Graphics USA for Iggesund Paperboard, to ask for some inside scoop on the technology of their paperboard performance and here’s what he said:
“We make a 3-ply product on a state-of-the art triple wire machine. The wet end of the machine was completely replaced in October 2007. This is the primary technology that allows for crack-free scores and folds with or against the grain, and even diagonal to the grain (see photo). The machine is fed by three separate head boxes which allows us to vary the fiber composition for each of the three layers.
“We use fully bleached fiber throughout (no mechanical fiber), but vary the percentages of long vs. short fiber. The outer layers (print surfaces) contain a higher percentage of short fiber providing a smooth surface for exceptional print reproduction. In the center ply we use a higher percentage of long fiber which provides the strength, durability, stiffness and yield advantages of an SBS (solid bleached sulfate) board grade. So, Invercote offers the characteristics of a board grade, but the print surface of a premium coated cover. As you might imagine, we are very well suited to high end cosmetic and pharmaceutical packaging, as well as high-quality brochures, book covers, and more.”
Neal clued me in to another interesting, and actually low-tech, secret to their paper quality—the geographic location of the trees. Apparently, it takes a pine or spruce tree almost twice as long to mature in the northern latitudes of Sweden (where all of their wood is harvested). The duration of development has a lot to do with the strength and resiliency of the fibers, both long and short. Who knew?
I had one more question for Neal, however. The three layer machine technology and the varying fiber technique was intriguing, but I sensed there must also be something special about the coating. I was right. Neal told me that they use a unique proprietary coating formulation. The coating composition is adjusted in two different general directions for the product family to satisfy printability requirements—primarily those of offset-litho and gravure printing. While he couldn’t reveal any trade secrets, he was able to tell me that the coating does not include any plastic or rubber (apparently many people ask about this).