1、Designation:D7734/D7734M13Standard 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 o
2、r,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 oxi
3、dative 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,
4、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 may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conf
5、ormancewith the standard.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 and health practices and determine the applica-bility of regulatory limitations prior
6、to use.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
7、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 r
8、epresentsthe 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
9、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,uni
10、formlylevel 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
11、 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 th
12、e ink or overprintvarnish 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)with1This test method is under
13、 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 Nov.1,2013.Published December 2013.DOI:10.1520/D7734_D7734M-13.Copyright ASTM International,100 Barr Harbor
14、 Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 sufficient 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 su
15、ggested test cycletime for most printing inks and overprint varnishes.NOTE2Optional shorter cycle times of 15 to 30 minutes may be moreapplicable for some fast drying inks or overprint varnishes.NOTE3It is important to have a record of temperature and relativehumidity as these parameters can have a
16、direct affect on the test results.8.6 At the end of each time interval,check the surfacecondition of the film surface by first touching a fingertip to thefilm and then to an adjacent clean portion of the glass next tothe ink or overprint drawdown.Use sufficient finger pressure toensure transfer of the ink or overprint varnish film to thefingertip.Do not use excessive pressure such that is wouldbreak through a film that has a dried surface(but is wetunderneath).Also do not twist the finger while
