Volume 04, Number 6
Dec 1991

Pressroom Concerns about Running Alkaline Papers

Glen Black is Vice President-Manufacturing, A.J. Kennedy & Co. Inc., Elmhurst, Illinois. His 19 years' experience in the forms industry includes work in dry-offset stock tab, custom continuous business forms, heat-set and ultraviolet high-color process printing and roll-to-roll laser personalization.

Reprinted with permission from FormsMfg., The Business Magazine of Forms Manufacturing, published by International Business Forms Industries, March 1991.

As one runs the press, it is important to monitor the pH constantly. Running with an alkaline-based sheet requires a neutral pH level of seven or lower. That is difficult to achieve because, inevitably, some calcium carbonate will leak into the fountain solution. If that happens, the pH will go from neutral reading to a base reading of eight. If, however, the solution is kept initially in a safe pH zone of four to six-which is slightly acidic-the calcium carbonate absorbed will only raise the pH to the neutral level of seven.

Forms manufacturers who convert to alcohol-fi-ee pressrooms understand the importance of changing fountain solution chemistry to achieve proper balance of inks, fountain solutions and rollers. Forms producers who run sheets that are alkaline-based and acid-based are facing the same need to develop inks and fountain solutions compatible with alkaline and acid grades.

Fountain solutions contain several basic ingredients:

• acids to reduce the pH level-which is the scale used to measure acidity or alkaline content-and maintain the sensitivity of both image and non-image areas;
• gum arabic to protect the non-image area from ink adherence;
• wetting agents to permit water to flow into nonimage areas;
• and plate conditioners to minimize the corrosive actions of the acid on the plate.

Each ingredient must remain in proper balance, even though the forms producer may run an acid-based sheet on one job and an alkaline-based sheet on the next job.

Contamination

Alkaline sheets have a tendency to pick surface lint or dust more than the acid-base sheets, which causes scratches on the plate. Alkaline sheets can be destructive to oily inks and may cause calcium carbonate to become embedded in the press rollers.

The key in running smoothly for alkaline and acid sheets is to understand pH level variations. To measure paper pH values the press operator should have a litmus pen [Graphic Technologies' Litmus Pen]. By marking the roll with a pen before it is mounted on press, the operator can determine the roll's acidity or alkaline content. If the pen produces a yellow mark, it is an acid sheet. A brown mark indicates a neutral pH level of seven and a blue mark indicates an alkaline sheet.

To maintain the correct pH balance and run a cleaner fountain solution, we installed a series of filters outside and inside the fountain solution tank. The first filter, a residential drinking-water filter system, is located outside the fountain tank. This filter contains a paper cartridge. It keeps materials that are picked from the paper out of the fountain solution tanks.

We added a second filter system that sits in the fountain solution tank. It is a PVC pipe, about four or five inches in length with a foam rubber cartridge. We drilled large holes in the PVC pipe to help pick up ink and to keep calcium carbonate out of the fountain solution.