preface
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This document has been prepared by Technical Committee ISO/TC 6, Paper, Board and Pulp, Subcommittee SC 2, Test Methods and Quality Specifications for Paper and Board.

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ISO TS 19857-2021 “Paper, board and printing inks – Laboratory test methods for setting offset inks for printability”

introduce
This document describes a test method for evaluating the ink setting characteristics of a specific ink/substrate combination in offset lithography.

Offset is the transfer of ink from the front of one piece of paper to the back or front of the next.

Solidification is the process by which low viscosity liquid ink components penetrate into a permeable substrate. These low viscosity liquids in inks are mineral oils, vegetable oils, or esters of vegetable oils. By separating from these low viscosity liquids, the remaining ink film solidifies. This is combined with changes in surface viscosity, depending on the ink-varnish system and time. Surface viscosity usually increases at the beginning of the setup and drops to zero later. The setting is the main drying mechanism of an ink system (e.g. press inks) or part of a multi-channel drying mechanism (e.g. traditional sheeting offset inks or thermosetting inks). The laboratory test used for setting up the interlining of the new print onto the non-printing substrate at a specified time. The transfer of ink to a non-printing substrate depends not only on the degree to which the ink solidifies through solidification, but also on the actual viscosity level of the original ink film. Therefore, the test result is a combination measurement.

The absorptive properties of paper have great influence on offset lithography. Improper absorption can lead to many printing problems, such as ink offset, poor adhesion, mottling, unpredictable increase in tone value, poor friction resistance, and damage to the first printing surface on the perfect press after perfection.

The more absorbent the paper is, the less time it takes for the ink to set sufficiently for further processing, but rapid ink setting will adversely affect other properties. When testing the processing of wet sheets, very short periods of time should be used, for example in a perfect press. Longer times are used for paper processing after printing, while longer times are used for further processing, such as folding and cutting.

According to the test purpose, there are three options for paper and ink combination:

Producing reference ink on paper;

— production ink on reference paper;

– Production ink on paper, according to the application of printed matter, can be divided into the following types:

— face to face offset (e.g. after folding offset);

Offset in front (for example, in a stack of paper).

ISO TS 19857-2021 “Paper, board and printing inks – Laboratory test methods for setting offset inks for printability”

1 range
This document describes a laboratory test method using an IGT1 or prufbau2 print-suitability tester for preparing samples to assess the absorption of ink on an offset substrate by setting a printed surface against an unprinted surface.

This method describes the use of ink volume to simulate monochromatic or multicolor printing. Printing and foil printing (counter printing) are done using intervals, between printing and counterprinting, that are common to the target process.

This method evaluates a specific ink and substrate combination.

2 Normative references
The following files are referenced in the text in such a way that some or all of the content constitutes the requirements of this document. For dated references, citation-only versions apply. For undated references, the latest version of the reference (including any revisions) applies.

ISO 5-4, Photographic and graphic techniques – Density measurement – Part 4: Geometric conditions for reflection density

ISO 2834-1, Graphic techniques – Laboratory preparation of test prints – Part 1: pasting inks

ISO 2846-1, Graphic technology – Colour and transparency of printing ink sets for four-colour printing – Part 1: sheetrope and thermoset web offset lithography

3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain databases of terms for standardization at the following addresses:

– ISO online browsing platform: iso.org/obp

— IEC electronic encyclopedia: available at electropedia.org/

3.1 Ink Setting

The drying of ink by absorption and/or oxidation

3.2 Offset

The effect that occurs when ink on a print is transferred from a printed surface to another surface

3.3 Foil paper

Reverse paper

Paper used to make counter prints for offset (3.2) assessment

3.4 Ink Film

< On the substrate. The amount of ink applied to the substrate surface to obtain the print optical density required for this test

Note 1: Quantities are specified in units of g/m2 or μm.

3.5 Ink Film

< On the printing mould. The amount of ink applied to the surface of the printing press to transfer to the substrate during the printing operation

Note 1: Quantities are specified in units of g/m2 or μm. The amount of ink film applied to the inking system is usually about twice the amount transferred to the substrate.

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