I have recently had the opportunity to review some data from plants that have applied a thin film of water to the lower double face liner on their corrugators. The film is applied just prior to the liner entering the hot plate section of the corrugator using a piece of equipment that can apply a very small amount of water, with an accurate and controllable consistency. I have been quite surprised at the results that these plants have documented. Here are a few of them.

Prevents Overheating. The film of water applied to the lower liner by the water deck prevented the liner from overheating. It seems as if the water acted like a thermal barrier that prevents the paper from becoming too hot. Reviewing some research done by the paper industry, it has been shown that paper begins to lose moisture around 165 to 185 degrees F. The film of water kept the liner at a constant temperature exiting the hot plates, right around 185 degrees. And it was possible to control the process for the temperature of the paper to stay constant regardless of grade, speed, and so forth.

Prevents Moisture Loss. We know that traditional hot corrugators heat the liner to 260 – 275 degrees F. Based upon what we know about temperature versus moisture in paper, this high temperature results in nearly bone dry paper. The bone dry paper then has a loss in strength, and becomes more brittle, according to paper industry research. But the data showed that the water film keeps the moisture in the paper nearly constant. This constant moisture has reduced the tendency for score cracking, warping, and washboarding caused by lack of sufficient moisture.

Improves Bonding. The water film created a steam vapor that is transmitted upward to the paper and starch. Plants observed that bonding was improved, and the need for precise heat regulation when changing grades or speed was not needed.

Lowers Starch Consumption. This was a big surprise. We didn’t expect lower starch consumption. Starch consumption was reduced below the levels that we expect with cooler corrugators. The moisture from the film of water lowered the water demand of the papers, which in turn lowered the amount of water needed from the starch formula to complete the bond.

Starch Application Rate is Constant. The starch consumption was constant – it was independent of speed and grade. These plants varied the application rate of the film of water to compensate for changes in speed and grade, but did not have to adjust the starch application rate.  This process separates the water needed by the paper from the water needed by the starch. The starch application rate became the same for light weight and heavy weight liners and mediums because the paper was kept at constant moisture.

The Need To Regulate Double Facer Heat Was Eliminated.  It was found that it was not necessary to regulate heat in the double facer when the water film was applied. The test plants either had older corrugators with hot plate sections that retain their heat for a long period of time, or had no heat regulation at all. The application rate of the water film was programmed to compensate for either the long period of time needed to change heat levels or the lack of adjustment of heat levels. For plants that did not have adjustable heat levels in the hot plates, the water application rate was used to make the adjustments to keep the paper at a constant temperature and moisture. For those plants with short times between grade changes, we believe that this method provides a means of adjusting the apparent heat to the paper without changing heat settings in the hot plate sections.