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Although often specific to paper, picking and loose contamination can sometimes be an interrelationship involving the entire printing process.

Definition

Although often specific to paper, picking and loose contamination can sometimes be an interrelationship involving the entire printing process. When these problems become pervasive rather than the exception, certain considerations may significantly broaden the operating window. Static electricity can cause loose contaminants to cling to the paper surface. This can be a problem when pressroom relative humidity is below 35% and when paper is not acclimated. The ideal range is 40-50% Rh.

pH
pH is the measure of the hydrogen ion content in water. Todays fountain solutions are buffered at 4.0 and do not change if you add more solution. As a press runs the pH will change depending on the compatibility of the ink with the fountain solution. An increase in pH means that the fountain solution is attacking the salts in the ink. If the rise continues unabated, then there will be problems with the plates because the solution is no longer buffered. Most plates are designed to run with fountain solution in a pH range of 3.8 to 4.2. When the pH rises above 4.2, the gum arabic will not adhere properly to the plate and becomes sensitive to ink causing scumming. Thusly, it is important to record pH reading to monitor the relationship of the fountain solution with ink. For quality printing, it is important to maintain the optimum pH for dampening systems.

Image area piling is a result of poor ink transfer, which is typically composed of a build-up of ink and/or paper components on the blanket.
Image area piling is a result of poor ink transfer, which is typically composed of a build-up of ink and/or paper components on the blanket. This build-up of material can increase in tack and may appear as mottle in screens and solids while progressively losing detail in tones.
Another form of piling is tail-edge pick or snap-outs occuring at the trailing edge of solid images. When this condition remains unchecked, the increasing tack build can pick the blanket apart or cause paper delamination. Piling usually suggests a systems incompatibility with fountain solution, ink, and paper. Lubrication at the point of blanket release in both image and non-image areas is vital in minimizing this concern by preventing the blanket from becoming too tacky.

Paper companies use calcium carbonate in the base-sheet as a filler and in the coating as a pigment. Most competitive sheets also use calcium carbonate as both filler and pigment.
Paper companies use calcium carbonate in the base-sheet as a filler and in the coating as a pigment. Most competitive sheets also use calcium carbonate as both filler and pigment. Calcium carbonate provides brightness and a more blue-white shade than clay. Calcium carbonate is used in neutral or alkaline paper making, which results in a more permanent sheet than acid paper making. Permanence is essential for reduced yellowing and brittleness of paper as it ages. This is especially important in the manufacturing of books. Acid sheets contain little, if any, calcium carbonate. This is due to the generation of foam when calcium dioxide is released from calcium carbonate in an acid environment. Therefore, acidic sheets typically contain more clay.

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2672 Hickory Grove Rd.
Acworth, GA, USA 30101
+1.800.241.7970
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In-House Machine Shop

Full service machine shop complete with in house CNC/Lathes. We have blueprints for over 1000 different cores.We can repair, rebuild or manufacture to OEM specs.

Our capabilities include:

  • New Core Fabrication
  • Journal Repairs
  • Center Hole Repairs
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