ASTM_D_7734_-_D_7734M_-_13_2020.pdf

Designation:D7734/D7734M13(Reapproved 2020)Standard Test Method forDetermination of Open Time of Oxidative Printing Inks andOverprint Varnishes by a Manual Method1This standard is issued under the fixed designation D7734/D7734M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers a manual procedure for deter-mining the stay open time of oxidative drying printing inks andoverprint varnishes by a finger transfer method.Open isdefined as a wet ink/varnish film.1.2 The amount of time required to reach the endpoint isrecorded in hours.1.3 Typical inks and overprint varnishes that dry by oxida-tion are oil based sheetfed offset,letterpress,and screen inks.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system are not necessarily exact equivalents;therefore,toensure conformance with the standard,each system shall beused independently of the other,and values from the twosystems shall not be combined.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Summary of Test Method2.1 Inks and overprint varnishes are applied to a glasssurface using a wet film applicator and checked at timeintervals using a finger transfer method to determine the timethat the ink/varnish are no longer open.3.Significance and Use3.1 When formulating printing inks and overprint varnishesthat dry primarily by oxidation it is important to know the stayopen time so that premature drying does not occur on theprinting press rollers and other components.3.2 The applied ink or OPV film used for testing is thickerthan the film printed on the substrate and nominally representsthe film on the printing press rollers.4.Apparatus4.1 Clean Dry Uniform Glass Plate,approximately 20 cmwide by 25 cm long 8 by 10 in.4.2 Machined Wet Film Applicator,with the appropriateclearance gap typically in a range of 12 to 75 m 0.5 to 3.0mils which provides a wet film thickness of 6 to 35 m 0.25to 1.5 mils.4.3 Stop Watch or Timer,with alarm.4.4 Ink Knife(s).5.Reagents and Materials5.1 Clean up Solvent.5.2 Clean up Rags.6.Preparation of Apparatus6.1 Ensure that the wet film applicator is clean and free ofnicks or other defects.6.2 Ensure that the glass plate surface is clean,uniformlylevel and free of any dust,solvent or residue.7.Conditioning7.1 Nominal laboratory standard conditions of 23 6 2C 736 3.5F temperature and 50 6 5%relative humidity level arerecommended for this test.Deviations from these conditionswill affect results.7.2 Glass plate should be located free from drafts orexcessive air movement.8.Procedure8.1 Select the appropriate clearance gap that will provide awet film thickness in the range of 12 to 75 m 0.5 to 3.0 milsor as agreed upon by seller and purchaser.8.2 Place the applicator on the glass and apply approxi-mately an 8 cm 3 in.wide sample of the ink or overprint1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.56 on Printing Inks.Current edition approved June 1,2020.Published July 2020.Originally approvedin 2013.Last previous edition approved in 2013 as D7734/D7734M 13.DOI:10.1520/D7734_D7734M-13R20.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.varnish in front of gap in the pulling direction.The amount ofink needs to be sufficient to produce a wet film about 15 to 20cm 6 to 8 in.long.8.3 Grasp the sides of the applicator with the fingers anddraw down at a uniform speed(approximately 25 mm/s)withsufficient pressure to maintain direct surface contact of theapplicator with the glass plate.8.4 Clean applicator immediately with cleaning solvent andrags.8.5 Set the timer for one hour.NOTE1One hour time intervals are the maximum suggested test cycletime for most pri