1、Designation: D7734/D7734M 13Standard 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 adoptio
2、n 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 t
3、ime 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,
4、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 may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may r
5、esult in non-conformancewith 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 regulator
6、y limitations prior 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 form
7、ulating 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 sub
8、strate 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 w
9、et 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 p
10、late 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 pl
11、ate 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-matel
12、y an 8 cm 3 in. wide sample of the 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
13、 mm/s) with1This 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 Nov. 1, 2013. Published December 2013. DOI:10.1520/D7734_D7734M-13.C
14、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1sufficient 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.
15、NOTE 1One hour time intervals are the maximum suggested test cycletime for most printing inks and overprint varnishes.NOTE 2Optional shorter cycle times of 15 to 30 minutes may be moreapplicable for some fast drying inks or overprint varnishes.NOTE 3It is important to have a record of temperature an
16、d relativehumidity as these parameters can have a 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. U
17、se 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 checking thetest specimens.NOTE 4Some test sa
18、mple film surfaces may exhibit a wet colorlessliquid referred to as “sweating.” This phenomena should be noted in thefinal report. Sweating may occur during the final film surface drying stagewith the use of higher levels of certain types of anti-oxidant compounds.8.7 Repeat step 8.6 every hour (or
19、other time interval asindicated in Note 2) as long as the ink or overprint varnish filmtransfers to the finger tip and then to the clean glass plate area.Always use a new area on the test film surface and glasssurface for each finger test.8.8 The ink or overprint varnish film is considered no longer
20、open when there is no transfer of ink or varnish to the fingertip.NOTE 5When the endpoint is approaching, the film may be tacky yetnot transfer to the finger. If this occurs, the applied film is no longerconsidered open.9. Report9.1 Open time is recorded as the number of hours elapsedbetween the ini
21、tial wet film application and when the ink/varnish no longer transfers to the finger.9.2 Record the laboratory test temperature and relativehumidity percentage.9.3 Record occurrence of sweating if observed.10. Precision and Bias10.1 PrecisionA round robin to supply reproducibilitydata is forthcoming
22、.10.2 BiasBias has not been determined at this time.11. Keywords11.1 open time; overprint varnishes; oxidation; printing inksASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are ex
23、pressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revi
24、sed, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you ma
25、y attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United Sta
26、tes. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D7734/D7734M 132
