Offset ink selection
Due to the non-absorbent surface of the substrate, printing sheet fed offset will require full oxidation type drying inks.
Printing with UV is also possible, but ensure the printer uses inks for PE film and not standard paper UV inks. This type of UV ink will never cure correctly and ink adhesion will be poor.
Damping must be kept to a minimum, avoid excess damping solution as this will retard ink drying. The damping solution should be around 5.5 to 6 Ph.
It is best to avoid fount additives; the use of distilled water without any fount additives would be an advantage.
Ink film weight
Heavy build up of ink film weights should be minimised, if possible use under colour removal as this will be of great use to reduce ink densities where colours are superimposed.
The delivery piles should be kept to a minimum height to avoid potential set off. Where possible it may be better to use a racking system in the delivery to avoid excessive stack height. Avoid press delivery joggers becoming set too tight against the printed stack, as excessive movement of the sheets could promote set off.
Non-vanishing grade of anti set off spray powder should be used; this is the starch-based powder. The use of a soluble type (sugar based) is not recommended.
For best results use a spray powder with a particle size of at least 25 micron.
Printed sheets should be allowed to dry fully prior to moving for further processing.
Backing up printed sheets can be carried out once the first side is completely dry, allow 12 hours between processing on the press.
Over varnishing is possible, but ensure that the varnish is suitable for non-absorbent materials. The use of inline coaters to seal the sheet with water based coatings can be carried out, ensure that the proposed sealer is designed for films/foils and that the heat setting for drying is correct.
If working with either a matt or gloss varnish, it would be a good option to carry out a test to ensure that any varnish used is suitable for the end application.
Prior to starting full press production, we would suggest that a press trial is carried out to ensure that correct ink settings are used for the main press run.
SHEET FED OFFSET INKS FOR POLYART IRIDESCENT
The following list is a guide only, the selection of ink for use with Polyart Iridescent is the responsibility of the printer.