ASTM_E_2228_-_10.pdf

Designation:E222810Standard Guide forMicroscopical Examination of Textile Fibers1This standard is issued under the fixed designation E2228;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.Scope1.1 This section describes guidelines for microscopicalexaminations employed in forensic fiber characterization,iden-tification,and comparison.Several types of light microscopesare used,including,stereobinocular,polarized light,compari-son,fluorescence,and interference.In certain instances,thescanning electron microscope may yield additional informa-tion.Select which test(s)or techniques to use based upon thenature and extent of the fiber evidence.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD276 Test Methods for Identification of Fibers in Textiles2.2 AATCC Standards:3AATCC Test Method 20:Qualitative Test Method 202007Fiber Analysis:Qualitative3.Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminology D123.3.2 Definitions of Terms Specific to This Standard:3.2.1 anisotropica characteristic of an object,which hasoptical properties that differ according to the direction in whichlight travels through the object when viewed in polarized light.3.2.2 barrier filtera filter used in fluorescence microscopythat suppresses unnecessary excitation light that has not beenabsorbed by the fiber and selectively transmits only light ofgreater wavelengths than the cut-off wavelength.3.2.3 Becke linethe bright halo near the boundary of afiber that moves with respect to that boundary as the fiber ismoved through best focus when the fiber is mounted in amedium that differs from its refractive index.3.2.4 Becke line methoda method for determining therefractive index of a fiber relative to its mountant by noting thedirection in which the Becke line moves when the focus ischanged.3.2.4.1 DiscussionThe Becke line will always move to-ward the higher refractive index medium(fiber or mountant)when the focal distance is increased and when the focaldistance is decreased away from the objective and will movetoward the lower refractive index medium when the sample ismoved toward the objective.3.2.5 birefringencethe numerical difference in refractiveindices for a fiber,given by the equation:ni n.Birefrin-gence can be calculated by determining the retardation(r)andthickness(T)at a particular point in a fiber and by using theequation:B 5 rnm!/1000Tmm!3.2.6 comparison microscopea system of two micro-scopes positioned side-by-side and connected via an opticalbridge in which two specimens may be examined simultane-ously in either transmitted or reflected light.3.2.7 compensatorany variety of optical devices that canbe placed in the light path of a polarizing microscope tointroduce fixed or variable retardation comparable with thatexhibited by the fiber;the retardation and sign of elongation ofthe fiber may then be determined.3.2.7.1 DiscussionCompensators may employ a fixedmineral plate of constant or varying thickness or a mineralplate that may be rotated,or have its thickness varied by tiltingto alter the thickness presented to the optical path(andretardation introduced)by a set amount.3.2.8 compensator,full wave(or red plate)a compensatorusually a plate of gypsum,selenite or quartz,which introducesa fixed retardation between 530 to 550 nm(approximately theretardation of the first order red color on the Michel-Levychart).1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current edition approved Sept.15,2010.Published October 2010.Originallyapproved in 2002.Last previous edition approved in 2002 as E2228 02.DOI:10.1520/E2228-10.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American Association of Textile Chemists and Colorists(AATCC),P.O.Box 12215,Research Triangle Park,NC 27709,http:/www.aatcc.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.9 compensator,quarter wavea compensator,usuallywith a mica plate,which introduces a fixed retardation between125 to 150 nm.3.2.10 compensator,quartz wedgea wedge,cut fromquartz,having continuously variable retardation extendingover several orders of interference colors(usually 3 to 7).3.2.11 compensator,Snarmonta quarter-wave plate in-serted above the specimen in the parallel“0”position with acalibrated rotating anal