ASTM_C_326_-_09_2014.pdf

Designation:C32609(Reapproved 2014)Standard Test Method forDrying and Firing Shrinkages of Ceramic Whiteware Clays1This standard is issued under the fixed designation C326;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the determination of linearshrinkage of ceramic whiteware clays,both unfired and fired.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 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 to use.2.Significance and Use2.1 The purpose of this test is to obtain values of shrinkageafter drying and firing of clays or bodies or both,under variousprocessing conditions to enable designers to determine theproper size of mold or die so as to produce a predeterminedsize of fired ware.3.Test Specimens3.1 Test specimens shall be round bars approximately 0.75in.(19 mm)in diameter by 5 in.(127 mm)in length.3.2 Test specimens may be prepared either by casting orplastic forming,as circumstances require.At least ten speci-mens shall be prepared.For cast specimens the molds may beeither one-piece,or two-or more-part molds;in either instancesufficient space shall be provided to allow solid casting withoutpiping.Where plastic-forming is employed,the clay-watermass shall be brought to a consistency that permits the makingof specimens rigid enough to allow careful handling withoutdistortion immediately after the test specimen is made.Plastic-formed test specimens shall be made either by extrusion or bypressing in a suitable metal mold.Where a vacuum pugmill isused,a vacuum of not less than 25 in.(635 mm)Hg shall bemaintained during the forming operation.Where no vacuumattachment is used,the plastic clay shall be thoroughly hand-wedged to eliminate entrapped air as a preliminary to formingtest pieces.3.3 The test specimens,cast or plastic-formed,shall besuitably identified and marked with shrinkage reference lines 4in.(102 mm)apart on the long axis of the specimen.Theshrinkage reference lines may conveniently be made with agage with knife edges at zero and 4 in.(102 mm)and markingmust be done as soon as the bars can be handled withoutdistortion.3.4 The marked specimens shall then be placed on a lightlyoiled pallet with semi-circular grooves 0.40 in.(10.2 mm)indiameter and allowed to dry at 68 to 100F(20 to 40C)for24h.The purpose of the semi-circular(half round)grooves is tomaintain straightness of the bars during drying.During thispreliminary drying period,the bars shall be turned 90 severaltimes at 2-h intervals to eliminate possible warping in thevertical direction.After the initial drying period,the specimensshall be placed in a drying oven at 200 to 230F(100 to 110C)and further dried for 24 h.3.5 The drying shrinkage of the test specimens should bedetermined in accordance with Sections 4 and 5.The speci-mens can now be fired according to a suitable firing scheduleto the desired temperature and the procedures of Sections 4 and5 applied to determine the total shrinkage.3.6 The test bars must be clearly identified as to whetherthey were cast or extruded,and shrinkage data likewiseidentified because of slight differences in shrinkage betweencast and extruded bars.4.Shrinkage Measurement4.1 Measure the distance between shrinkage referencemarks on dried or fired specimens to the closest 0.004 in.(0.1mm)with calipers of suitable accuracy.Record the average ofat least ten measurements(one measurement on each of thegroup of ten or more specimens).5.Calculation5.1 Calculate the linear drying shrinkage as a percentage ofplastic length,as follows:Sd5Lp2 LdLp3100(1)1This test method is under the jurisdiction ofASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.04 on Raw Materials.Current edition approved Dec.1,2014.Published December 2014.Originallyapproved in 1953.Last previous edition approved in 2009 as C326 09.DOI:10.1520/C0326-09R14.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:Sd=linear drying shrinkage,%,Lp=plastic length of test specimen,andLd=dry length of test specimen.5.2 Calculate the total linear shrinkage after drying andfiring of clay shrinkage specimens as a percentage of plasticlength,as follows:St5Lp2 LfLp3100(2)where:St=total linear shrinkage after drying