ISO 12647-9:2021

Graphic technology - Process control for the production of half-tone colour separations, proof and production prints - Part 9: Metal decoration printing processes using offset lithography

This document specifies requirements for systems that are used to produce offset prints for process colour reproduction on metallic substrates, which have been printed with a white coating. It is intended for flat printed sheet metal applications. It does not cover shaped or pre-formed metal such as pre-formed cans. Recommendations are provided with regard to appropriate test methods associated with these requirements. This document differs from the method used to produce an offset print on paper or board in ISO 12647-2 in that it considers the colour values of a typical white coated metal substrate intended for metal decoration, using offset lithography and substrates that are independent of backing colour.

Technologie graphique — Maîtrise des procédés pour la fabrication des séparations couleur, des épreuves et des tirages en ton tramé — Partie 9: Impression décorative sur métal avec un procédé offset lithographique

General Information

• Status: Published
• Publication Date: 28-Jun-2021
• ICS: 37.100.01 - Graphic technology in general
• Technical Committee: ISO/TC 130 - Graphic technology
• Drafting Committee: ISO/TC 130/WG 3 - Process control and related metrology
• Current Stage: 6060 - International Standard published
• Start Date: 29-Jun-2021
• Due Date: 03-Nov-2021
• Completion Date: 29-Jun-2021

Overview

ISO 12647-9:2021 - Graphic technology - Process control for the production of half-tone colour separations, proof and production prints - Part 9: Metal decoration printing processes using offset lithography - defines process-control requirements for producing accurate offset-printed imagery on flat, white-coated metallic substrates. It addresses colour separation, proofing, production prints and associated measurement methods specific to metal decoration printing (flat sheet metal), and clarifies how this differs from paper/board workflows covered in ISO 12647-2.

Key topics and technical requirements

• Scope and substrate: Applies to flat metal sheets pre-coated with an opaque white coating (not pre-formed cans or bare metal).
• Printing condition definition: Characterization data sets, ICC output profiles or specified printing condition descriptions are required to define aims and tolerances.
• Data delivery and formats: CMYK or three-component colour data recommended; exchange via PDF/X is preferred. ICC profiles and rendering intent must be communicated.
• Proofing and conformance: Digital proofs, press proofs or OK prints should accompany job data. Conformance tests and aim values (tone curves, solids, substrate colour) are specified.
• Screening and plates: Guidance on screen frequency (ruling), plate-setter resolution (e.g., resolution to reproduce ≥150 tone value steps), dot shape/size, screen angle and tone value sum.
• Tone reproduction controls: Limits for tone value increase/spread, grey reproduction and grey balance to ensure neutrals print correctly on a white-coated metal substrate.
• Measurement methods and control strips: Procedures for computing densities, CIELAB coordinates and CIELAB differences; recommended control-strip measurements for process control.
• Spot colours: Allowed but tolerances are to be agreed between buyer and seller; spot-colour data exchange using ISO 17972 schemas is referenced.

Practical applications and users

ISO 12647-9 is essential for:

• Metal packaging printers (boxes, flat sheet metal decoration)
• Prepress and colour management specialists creating ICC profiles and characterization data
• Brand owners and specification writers who require consistent colour reproduction on metal
• Proofing houses, press operators and quality managers implementing process control and measurement routines
• Ink, plate and substrate suppliers developing compliant materials and test methods

Benefits include improved proof-to-press matching, predictable neutral/grey reproduction on white-coated metal, reduced rework and standardized communication of printing conditions.

Related standards

• ISO 12647-1 (general parameters and measurement methods)
• ISO 12647-2 (offset on paper/board - for comparison)
• ISO 12642-1 / ISO 12642-2 (characterization input data)
• ISO/TS 10128 (data adjustment methods)
• ISO 13655 (spectral measurement)
• ISO 15076-1 (ICC profile format)
• ISO 17972-1 / -4 (spot colour spectral data exchange)

Keywords: ISO 12647-9:2021, metal decoration printing, offset lithography, process control, colour separations, proofing, white coated metal, ICC profile, PDF/X, tone value, screen frequency, control strip, grey balance.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 12647-9
First edition
2021-06
Graphic technology — Process control
for the production of half-tone colour
separations, proof and production
prints —
Part 9:
Metal decoration printing processes
using offset lithography
Technologie graphique — Maîtrise des procédés pour la fabrication
des séparations couleur, des épreuves et des tirages en ton tramé —
Partie 9: Impression décorative sur métal avec un procédé offset
lithographique
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 2
4.1 General . 2
4.2 Data files and printing forms . 2
4.2.1 Data delivery . 2
4.2.2 Printing forme quality . 3
4.2.3 Screen frequency (periodic screens) . 3
4.2.4 Dot size (non-periodic screens) . 3
4.2.5 Screen angle (periodic screens) . 3
4.2.6 Dot shape and its relationship to tone value (periodic screens) . 4
4.2.7 Tone value sum . 4
4.2.8 Grey reproduction and grey balance . 4
4.3 Proof or production print . 4
4.3.1 General. 4
4.3.2 Visual characteristics of image components — Print substrate colour . 5
4.3.3 Ink set colours (colorant description) . 6
4.3.4 Tone value reproduction limits . 7
4.3.5 Tone value increase and spread . 7
4.3.6 Tolerance for image positioning .10
4.3.7 Conformance .10
5 Measurement methods .11
5.1 Computation of densities, CIELAB colour coordinates and CIELAB colour differences .11
5.2 Control strip .11
Annex A (informative) Grey reproduction and grey balance .12
Annex B (informative) Handling differences in coating colour .14
Bibliography .15
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 130, Graphic technology.
A list of all parts in the ISO 12647 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

Introduction
ISO 12647-1 serves to provide definitions, general principles, the general order and materials to be
covered in ISO 12647-2 to ISO 12647-9, the definition of the data, the measurement conditions, and the
reporting style.
This document relates to the subject of offset printing on coated metallic substrates and establishes
the printing requirements for the metal decoration market. This market includes metal boxes and
cans in which the printing is performed directly onto the white coated surface of the metal prior to the
formation of a container.
This document specifies aim values (or sets of aim values) and tolerances, for the primary parameters
specified in ISO 12647-1 for digital proof printing. Primary parameters that define a printing condition
include screening parameters (where applicable), the colours of the solids, the colour of the print
substrate, colours of intermediate tint values and the tone curve. Adherence to these values essentially
ensures that a grey which at the colour separation stage was composed for a specified printing
condition also prints as a grey colour when both proofing and printing. Remaining deviations from grey
due to differences in trapping can then be removed by adjusting the colouration within the tolerances
provided. This document also specifies test methods for those properties of prints and their substrates
that are considered relevant for stable and reliable metal deco reproduction.
Typically, the specified printing condition is defined through an International Color Consortium
(ICC) profile or the associated characterisation data set, both of which relate the source data and the
colorimetrically defined printed colour. Such data can be derived from printing conditions conforming
to the pertinent process standard of ISO 12647 (all parts) by industry trade groups or individuals.
Printing on metallic substrates poses unique challenges. Sometimes, the metal surface is pre-coated
with an opaque white and then the coloured inks are printed on top of the white coating. Other times,
the coloured inks are printed directly onto the metallic surface and the nature of the bare metal,
shininess, texture or polishing marks can be observed and measured through the ink layer. Most
metallic substrates are electrolytic tinplate (ETP), tin free steel (TFS) and aluminium, all coated with
a white coating or pre-printed with a printing white ink before being printed with coloured inks. This
document considers only the substrates, which are pre-coated with a white coating.
Historically, there has been no consistency in the way that either the characterisation data or the
criteria and limits for a satisfactory match have been provided. This has led to significant redundancy
and inconsistencies in the evaluation of proofing systems for different, but similar, applications, and a
cost and time burden on the industry. This document therefore attempts to provide guidance in this
area by providing specifications and associated testing procedures.
This document defines requirements for printing offset on metallic substrates that have been pre-
coated with a white coating. Bare metallic substrates have not been included because of the complexity
of the specular and surface reflection requirements. Also, the grey nature of the substrate means that
it will always be restricted in gamut and difficult to manage. The industry does not print much process
imagery on bare metal.
This document does not specifically consider the production of spot colours from a process printing
approach. However, such colours can be generated from such an approach and the tolerances should be
agreed between the buyer and the seller. Spot colour management is defined in this document to utilize
[1] [2]
spectral data in an .xml schema defined by ISO 17972-1 and ISO 17972-4 . ISO 17972-4 includes
exchange specifications for spot colour characterization data to facilitate the communication of spot
colour data.
INTERNATIONAL STANDARD ISO 12647-9:2021(E)
Graphic technology — Process control for the production
of half-tone colour separations, proof and production
prints —
Part 9:
Metal decoration printing processes using offset
lithography
1 Scope
This document specifies requirements for systems that are used to produce offset prints for process
colour reproduction on metallic substrates, which have been printed with a white coating. It is intended
for flat printed sheet metal applications. It does not cover shaped or pre-formed metal such as pre-
formed cans. Recommendations are provided with regard to appropriate test methods associated with
these requirements.
This document differs from the method used to produce an offset print on paper or board in ISO 12647-2
in that it considers the colour values of a typical white coated metal substrate intended for metal
decoration, using offset lithography and substrates that are independent of backing colour.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/TS 10128, Graphic technology — Methods of adjustment of the colour reproduction of a printing
system to match a set of characterization data
ISO 12642-1, Graphic technology — Input data for characterization of four-colour process printing —
Part 1: Initial data set
ISO 12642-2, Graphic technology — Input data for characterization of 4-colour process printing — Part 2:
Expanded data set
ISO 12647-1:2013, Graphic technology — Process control for the production of half-tone colour separations,
proof and production prints — Part 1: Parameters and measurement methods
ISO 12647-7, Graphic technology — Process control for the production of halftone colour separations, proof
and production prints — Part 7: Proofing processes working directly from digital data
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts
images
ISO 15076-1, Image technology colour management — Architecture, profile format and data structure —
Part 1: Based on ICC.1:2010
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12647-1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
total print area
ratio of the area covered with ink to the entire area in an ink zone
3.2
characterization data
set of tone values and associated colorimetric values that fully describe a given printing process
3.3
metal decoration
printing on metals to produce a graphic image on the metal surface
Note 1 to entry: The term does not exclude printing on metal for functional or promotional reasons.
3.4
spot colour
non-process colour that is used in addition to, or in place of, a process colour and is normally applied
with a single impression
Note 1 to entry: When associated with a corporate product identity, a spot colour is also known as brand colour.
4 Requirements
4.1 General
Digital data files delivered for printing should be accompanied by a digital proof print, a press proof
print, or an OK print from a previous print run.
Press proof prints are test prints of the data files on a printing press which may serve as a reference for
subsequent printing. While most proofs are digital proofs, for colour- or content-critical work there is a
need for press proof prints with the same setup as the production print.
4.2 Data files and printing forms
4.2.1 Data delivery
Data delivered for printing shall be in the colour formats CMYK or three-component and should be
exchanged using PDF/X data formats.
The intended printing condition shall be indicated. In case of PDF/X, the mechanisms provided by the
specified data format shall be used.
In case of other data formats, a printing condition description, a characterization data set in accordance
with ISO 12642-1 and ISO 12642-2, or an International Colour Consortium (ICC) output profile in
accordance with ISO 15076-1, shall be communicated.
If the data are other than CMYK, the data shall be defined by colorimetric descriptions using an ICC
profile or another mechanism and an ICC CMYK output profile shall be included. The rendering intent to
be used for each data element shall be communicated.
If the characterization data or ICC output profile provided conflicts with the printing conditions
defined in this document, one of the methods defined in ISO/TS 10128 shall be used for data adjustment
prior to print production. The aims for process control should be taken from characterization data, if
agreed between all parties. Where this is done, densitometric tone values are not usually available and
2 © ISO 2021 – All rights reserved

colorimetric tone values should be used. Further information on the relationship between colorimetric
and densitometric tone values can be found in ISO/TS 10128.
NOTE A printing condition is defined here as a print substrate description, a colorant description, a screening
description, an ink set and a printing sequence.
Quality control of the content of a print job prior to final production checks are recommended since
PDF/X conformance does not necessarily ensure a suitable image resolution or other production
dependent criteria.
Additional spot colours are allowed, however, this document does not make provisions for tolerances.
4.2.2 Printing forme quality
The resolution of the plate setter should be selected to ensure that at least 150 tone value steps are
reproduced.
For a screen employing single half-tone cell modulation, for example, if the intended nominal screen
−1 −1
ruling is 80 cm , the resolution of the plate setter should not be less than 1 000 cm . For a screen with
super-cell technology, it is possible to set the resolution to a smaller value.
4.2.3 Screen frequency (periodic screens)
For four-colour work, the screen frequency (screen ruling) for periodic screens should be within the
−1 −1 −1
range from 48 cm to 80 cm ; 69 cm (175 lines per inch) is the most common plate frequency.
NOTE 1 The screen frequency is often varied slightly from one process colour to another in order to minimize
moiré patterns. For example, there can be a difference of up to 6 % of the nominal screen frequency between the
colours C, M, Y.
NOTE 2 For the black or yellow colour halftone, a screen frequency is sometimes used which is substantially
−1 −1
finer than the nominal screen ruling of the remaining colours, for example, 84 cm versus 60 cm .
Screen frequencies are often required or given in lpi (lines per inch). To convert between screens per
cm and lines per inch a conversion factor of 2,54 should be used.
The requirement 4.2.3 given in lpi reads as follows (rounded to commonly used integral numbers): for
four-colour work, the screen frequency (screen ruling) for periodic screens should be within the range
from 120 lpi to 200 lpi.
4.2.4 Dot size (non-periodic screens)
For four-colour work, the screen dot size for non-periodic screens shall be within the range 20 µm to
40 µm and should be within the range 20 µm to 30 µm.
NOTE Outside of the range 20 µm to 40 µm, the general principles specified in ISO 12647-1 remain valid but
specific values can differ.
4.2.5 Screen angle (periodic screens)
For half-tone dots without a principal axis, the nominal difference between the screen angles for cyan,
magenta and black should be 30°, with the screen angle of yellow separated at 15° from another colour.
The screen angle of the dominant colour should be 45°.
For half-tone dots with a principal axis, the nominal difference between screen angles for cyan, magenta
and black should be 60°, with the screen angle of yellow separated by 15° from another colour. The
screen angle of the dominant colour should be 45° or 135°.
4.2.6 Dot shape and its relationship to tone value (periodic screens)
For periodic screens, circular, square or elliptical half-tone dot shapes should be used. For half-tone
dots with elliptical dot shape, the first link-up should occur no lower than at 40 % tone value and the
second linkup no higher than at 60 % tone value.
4.2.7 Tone value sum
Tests should be run to determine tone value sum, depending on the printing equipment, and drying,
tone value sum should not exceed 300. This should be tested on production equipment.
NOTE Press problems can be encountered at high levels of tone value sum. There can be poor ink trapping,
back transfer and set-off due to insufficient ink drying.
4.2.8 Grey reproduction and grey balance
The tone values of cyan, magenta and yellow that lead to a visually neutral grey should be calculated
from the standard printing condition or actual printing condition or the associated profiles by
Formulae (1) and (2) describing the grey reproduction (L*, a*, b*) w
...