Polylith Synthetic Paper Printing Tips
Polylith is the printer-friendly synthetic paper that easily creates bright and vibrant graphics on lithography, flexo, letterpress, and screen presses. The following printing tips and techniques briefly summarize our experience and recommendations. Be sure to take a look at our finishing tips as well.
Offset and Letter Press
Standard paper inks can be applied in most cases; however, it is recommended that a test be carried out prior to printing. Sharp prints with excellent reproduction of line and tone detail can be readily obtained using a screen size of up to 175 mesh. When satisfactory standard paper ink is not available, the use of special inks is recommended.
High solids inks are a good choice, and complete drying is recommended prior to additional processing to avoid ink distortion and offsetting. The leading ink manufacturers have been consulted and inks are available for lithographic, flexographic, letterpress, and screen-printing.
For regular jobs, many standard paper inks are satisfactory, provided the ink-water balance is reasonably well controlled. When close register multi-color work is involved, the use of standard paper inks with their high solvent content may result in unacceptable print distortion, especially on the lighter weights.
In these cases, it is recommended that high solids special inks be used which have a very low mineral oil content, and are allowed to dry entirely by oxidation.
1. The most suitable printing speed is 8,000 – 10,000 sheets.
2. Before feeding, it will be best if you can fan the sheets or blow air to separate the sheets.
3. If the humidity is low, it is easy to generate static. When feeding Polylith maintain the relative humidity above 50%, and use anti-static equipment to control static. The location of static ionization units will have an effect on their functioning. The use of static eliminating tinsel on the delivery section can also help reduce static build-up.
Metal plates and pre-sensitized plates are preferable, although paper/melinex plates may be used. Care should be taken when using paper/melinex plates, as some fount additives may retard or inhibit drying. Experience has shown that plates with a surface grain (anodized) will enable the printer to obtain better control of dampening than plates with a grained surface.
Fountain Solution and Dampening
Control of dampening is the most important factor affecting the litho print quality. Use a 11% – 15% alcohol fountain system, or you can add other alcohol substitute additives to the fountain system, which will improve print quality. It is recommended that the PH value of the fountain solution be maintained between 5.5- 6.0. Temperature should be maintained between 48F – 59F (9C – 15C). Because Polylith is not absorbent as paper, the amount of water on the plate should be reduced 10 -20%, or it will be slow to dissipate and will retard ink drying.
Anti Set-Off Spray
It is recommended that a fine spray powder be used with a particle size of 400 mesh, instead of the regular 300 mesh and non-varnishing, starch-based type. Please be advised that varnishing grades or soluble powders are not recommended, because these types can’t provide adequate protection against set-off.
It is recommended that the height of synthetic paper piled on the paper receiver shelf should not exceed 7-8 inches. A desirable height is about 6 – 7 inches. Paper stack height is generally about 9 inches. Leave the printed stack undisturbed until dry.
Allow at least 3 – 5 hours drying time before further printing to avoid ink offsetting. Also allow at least 12 hours for complete drying before cutting, coating and processing. UV drying methods with the appropriate UV inks, as well as electron beam and infrared drying methods can reduce drying time. During drying, the temperature should not exceed 150F to maintain dimensional stability. Print Pressure – Can be reduced 5-10% as compared to paper.
Oxidizing inks that dry by evaporation are recommended. Inks drying by oxidation should be put on racks. If ovens are used for drying, temperatures should not exceed 160F, and be constant. Always use the finest screen and thinnest ink film for the best results.
Polylith can be readily printed by flexography. Both solvent based and water based inks are suitable and available from most ink suppliers.
Polylith synthetic papers can be printed on sheet or roll fed gravure presses, approved inks are available from most ink suppliers