ASTM D7734/D7734M-13(2020)

Standard Test Method for Determination of Open Time of Oxidative Printing Inks and Overprint Varnishes by a Manual Method

SIGNIFICANCE AND USE
3.1 When formulating printing inks and overprint varnishes that dry primarily by oxidation it is important to know the stay open time so that premature drying does not occur on the printing press rollers and other components.  
3.2 The applied ink or OPV film used for testing is thicker than the film printed on the substrate and nominally represents the film on the printing press rollers.
SCOPE
1.1 This test method covers a manual procedure for determining the stay open time of oxidative drying printing inks and overprint varnishes by a finger transfer method. Open is defined as a wet ink/varnish film.  
1.2 The amount of time required to reach the endpoint is recorded in hours.  
1.3 Typical inks and overprint varnishes that dry by oxidation are oil based sheetfed offset, letterpress, and screen inks.  
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2020
• ICS: 87.040 - Paints and varnishes
• ICS: 87.080 - Inks. Printing inks
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.56 - Printing Inks

Relations

• Replaces: ASTM D7734/D7734M-13 - Standard Test Method for Determination of Open Time of Oxidative Printing Inks and Overprint Varnishes by a Manual Method
• Effective Date: 01-Jun-2020

Overview

ASTM D7734/D7734M-13(2020): Standard Test Method for Determination of Open Time of Oxidative Printing Inks and Overprint Varnishes by a Manual Method establishes a reliable procedure for measuring the open time, or "stay open time," of oxidative drying printing inks and overprint varnishes. This manual test method uses a finger transfer technique on a glass plate to gauge how long a wet film of ink or varnish remains transferable, representing conditions found on printing press rollers. The standard is critical for ink formulators, printers, and manufacturers to ensure optimal performance, minimize premature drying, and achieve consistent print quality.

Key Topics

• Open Time of Inks and Varnishes: Defines "open" as the period an ink or varnish remains wet and transferable, preventing drying on press components.
• Finger Transfer Method: Describes a manual procedure to assess open time by periodic finger testing of a drawn-down wet film.
• Equipment & Materials: Utilizes a clean, uniform glass plate and a machined wet film applicator to create consistent sample films. The recommended film thickness exceeds that which is typically applied to substrates during printing, simulating the ink film on press rollers.
• Measurement Precision: Requires interval testing, often at one-hour intervals, and measurement of elapsed time until no further transfer occurs.
• Environmental Factors: Notes the influence of temperature and humidity on results, recommending standard laboratory conditions for consistency.
• Safety & Regulatory: Advises users to develop appropriate safety, health, and environmental practices for solvent and ink handling.

Applications

ASTM D7734/D7734M-13(2020) provides valuable guidance for the following practical uses:

• Printing Ink and Varnish Formulation: Ink and OPV manufacturers use this standard to develop and quality control oxidative drying products, ensuring they remain workable during the entire print run.
• Process Optimization: Printing facilities apply this method to evaluate and select inks and overprint varnishes that optimize performance and reduce press stoppages due to premature drying.
• Quality Assurance: Offers a benchmark for documenting and auditing ink and varnish properties, enabling buyers and sellers to specify and verify product open time.
• Research and Development: Facilitates comparative studies of new raw materials, additives, or formulations designed to extend or control drying times.

Industries that benefit from this standard include:

• Commercial and packaging printing
• Offset, letterpress, and screen printing operations
• Ink and varnish manufacturing
• Independent testing laboratories

Related Standards

Understanding and using ASTM D7734/D7734M-13(2020) can be complemented with these related standards and resources:

• ASTM D01: Committee on Paint and Related Coatings, Materials, and Applications
• ASTM Standards for Printing Inks: Related standards cover methods for ink drying time, adhesion, and performance.
• ISO and International Standards: For broader guidance, refer to analogous ISO standards on printing ink evaluation.
• WTO TBT Guidelines: This standard aligns with principles set forth by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

By following ASTM D7734/D7734M-13(2020), professionals across the printing supply chain can ensure that oxidative drying inks and varnishes perform reliably, helping to avoid costly downtime and ensuring high-quality printed products.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7734/D7734M − 13 (Reapproved 2020)
Standard Test Method for
Determination of Open Time of Oxidative Printing Inks and
Overprint Varnishes by a Manual Method
This standard is issued under the fixed designation D7734/D7734M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope open time so that premature drying does not occur on the
printing press rollers and other components.
1.1 This test method covers a manual procedure for deter-
mining the stay open time of oxidative drying printing inks and
3.2 The applied ink or OPV film used for testing is thicker
overprint varnishes by a finger transfer method. Open is than the film printed on the substrate and nominally represents
defined as a wet ink/varnish film.
the film on the printing press rollers.
1.2 The amount of time required to reach the endpoint is
4. Apparatus
recorded in hours.
4.1 Clean Dry Uniform Glass Plate, approximately 20 cm
1.3 Typical inks and overprint varnishes that dry by oxida-
wide by 25 cm long [8 by 10 in.].
tion are oil based sheetfed offset, letterpress, and screen inks.
4.2 Machined Wet Film Applicator, with the appropriate
1.4 The values stated in either SI units or inch-pound units
clearance gap typically in a range of 12 to 75 µm [0.5 to 3.0
are to be regarded separately as standard. The values stated in
mils] which provides a wet film thickness of 6 to 35 µm [0.25
each system are not necessarily exact equivalents; therefore, to
to 1.5 mils].
ensure conformance with the standard, each system shall be
4.3 Stop Watch or Timer, with alarm.
used independently of the other, and values from the two
systems shall not be combined.
4.4 Ink Knife(s).
1.5 This standard does not purport to address all of the
5. Reagents and Materials
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5.1 Clean up Solvent.
priate safety, health, and environmental practices and deter-
5.2 Clean up Rags.
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor-
6. Preparation of Apparatus
dance with internationally recognized principles on standard-
6.1 Ensure that the wet film applicator is clean and free of
ization established in the Decision on Principles for the
nicks or other defects.
Development of International Standards, Guides and Recom-
6.2 Ensure that the glass plate surface is clean, uniformly
mendations issued by the World Trade Organization Technical
level and free of any dust, solvent or residue.
Barriers to Trade (TBT) Committee.
2. Summary of Test Method 7. Conditioning
2.1 Inks and overprint varnishes are applied to a glass 7.1 Nominallaboratorystandardconditionsof23 62°C[73
surface using a wet film applicator and checked at time 6 3.5°F] temperature and 50 6 5 % relative humidity level are
intervals using a finger transfer method to determine the time recommended for this test. Deviations from these conditions
that the ink/varnish are no longer open. will affect results.
7.2 Glass plate should be located free from drafts or
3. Significance and Use
excessive air movement.
3.1 When formulating printing inks and overprint varnishes
that dry primarily by oxidation it is important to know the stay
8. Procedure
8.1 Select the appropriate clearance gap that will provide a
This test method is under the jurisdiction of ASTM Committee D01 on Paint
wet film thickness in the range of 12 to 75 µm [0.5 to 3.0 mils]
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.56 on Printing Inks. or as agreed upon by seller and purchaser.
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved
8.2 Place the applicator on the glass and apply approxi-
in 2013. Last previous edition approved in 2013 as D7734/D7734M – 13. DOI:
10.1520/D7734_D7734M-13R20. mately an 8 cm [3 in.] wide samp
...