Papers

Posted on 11-27-2013 by Admin

Some papers are very adaptable to several applications, while others others are very limited. The next section will briefly discuss the types of paper that are acceptable for different printing processes and applications.

Paper for gravure.  Generally, gravure produced newsprint will contain mineral fillers and a calendered surface. Many mail order catalogs are a good example of this type of stock.

When higher quality is desired, the paper also uses mineral filler but with a greater percentage of the chemical pulp with short fibers.

The surfaces of the paper can be relatively softer since the gravure ink is not tacky. This eliminates the problem of picking fibers from the surface of the paper.

Coated surfaces are now very evident in gravure. The compressibility of the paper is important as the gravure cells must make contact with the paper surface.

Since packaging is also involved with the gravure process, the surface must be excellent and the stock must have dimensional stability. The thickness must also be controlled. The moisture content is another major factor to be considered with gravure.

Satisfactory printing of the stock and its reaction to the process is critical to quality and high production speeds required of gravure.

Paper for offset lithography.  In offset lithography, one of the primary paper considerations must be the limitation of fuzz, lint, or dust. A wide variety of paper can be printed by the planographic process, but they must have sufficient fiber bonding strength to prevent the pulling of fibers from the stock. Because of the surface contact and the tackiness of the ink, special coatings are normally placed on the paper.

Moisture is another consideration since it comes in contact with the surface. The paper surface cannot be weakened by moisture so that fibers pick off with each successive impression.

Surface irregularity is not critical since the blanket is resilient and shoud return to its original shape after many impressions, even if the paper has an irregular surface. Of course, limitations do exist.

When in doubt, seek advice from a reputable firm. Paper has been developed to cover a wide range of uses.

Paper for letterpress.  The relief process uses a large amount of newsprint but a great many paper grades exist for the relief process.

Rough stocks are NOT recommended because of the positive contact, high pressure required to make complete ink coverage. Very hard, smooth paper surfaces are excellent for high quality line and halftone work.

New types of inks and drying processes have forced the paper manufacturer to produce new types of paper to withstand additional punishment.

Coatings have greatly improved the surface but it has also forced a higher degree of surface levelness.

Paper for screen printing.  Many kinds of paper can be used for screen printing. The end use is the most important factor to be considered. Will it be used outside as a bumper sticker or inside as a poster?