ASTM D7734/D7734M-13

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Designation: D7734/D7734M − 13
Standard Test Method for
Determination of Open Time of Oxidative Printing Inks and
1
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 4. Apparatus
1.1 This test method covers a manual procedure for deter- 4.1 Clean Dry Uniform Glass Plate approximately 20 cm
mining the stay open time of oxidative drying printing inks and wide by 25 cm long [8 by 10 in.].
overprint varnishes by a finger transfer method. Open is
4.2 Machined Wet Film Applicator with the appropriate
defined as a wet ink/varnish film.
clearance gap typically in a range of 12 to 75 µm [0.5 to 3.0
1.2 The amount of time required to reach the endpoint is mils] which provides a wet film thickness of 6 to 35 µm [0.25
recorded in hours. to 1.5 mils].
1.3 Typical inks and overprint varnishes that dry by oxida- 4.3 Stop Watch or Timer with alarm.
tion are oil based sheetfed offset, letterpress, and screen inks.
4.4 Ink Knife(s).
1.4 The values stated in either SI units or inch-pound units
5. Reagents and Materials
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each
5.1 Clean up Solvent.
system shall be used independently of the other. Combining
5.2 Clean up Rags.
values from the two systems may result in non-conformance
with the standard.
6. Preparation of Apparatus
1.5 This standard does not purport to address all of the
6.1 Ensure that the wet film applicator is clean and free of
safety concerns, if any, associated with its use. It is the
nicks or other defects.
responsibility of the user of this standard to establish appro-
6.2 Ensure that the glass plate surface is clean, uniformly
priate safety and health practices and determine the applica-
level and free of any dust, solvent or residue.
bility of regulatory limitations prior to use.
7. Conditioning
2. Summary of Test Method
7.1 Nominallaboratorystandardconditionsof23 62°C[73
2.1 Inks and overprint varnishes are applied to a glass
6 3.5°F] temperature and 50 6 5 % relative humidity level are
surface using a wet film applicator and checked at time
recommended for this test. Deviations from these conditions
intervals using a finger transfer method to determine the time
will affect results.
that the ink/varnish are no longer open.
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
open time so that premature drying does not occur on the
8.1 Select the appropriate clearance gap that will provide a
printing press rollers and other components.
wet film thickness in the range of 12 to 75 µm [0.5 to 3.0 mils]
3.2 The applied ink or OPV film used for testing is thicker or as agreed upon by seller and purchaser.
than the film printed on the substrate and nominally represents
8.2 Place the applicator on the glass and apply approxi-
the film on the printing press rollers.
mately an 8 cm [3 in.] wide sample of the ink or overprint
varnish in front of gap in the pulling direction. The amount of
1 ink needs to be sufficient to produce a wet film about 15 to 20
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of cm [6 to 8 in.] long.
Subcommittee D01.56 on Printing Inks.
8.3 Grasp the sides of the applicator with the fingers and
Current edition approved Nov. 1, 2013. Published December 2013. DOI:
10.1520/D7734_D7734M-13. draw down at a uniform speed (approximately 25 mm/s) with
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D7734/D7734M − 13
sufficient pressure to maintain direct surface contact of the transfers to the finger tip and then to the clean glass plate area.
applicator with the glass plate. Always use a new area on the test film surface and glass
surface for each finger test.
8.4 Clean applicator immediately with cleaning solvent and
rags.
8.8 Theinkoroverprintvarnishfilmisconsiderednolonger
open when there is no transfer of ink or varnish to the fingertip.
8.5 Set the timer for one hour.
NOTE 5—When the endpoint is approaching, the film may be tacky yet
NOTE 1—One hour time intervals are the maximum suggested test cycle
not transfer to the finger. If this occurs, the applied film is no l
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