ASTM E2808-21a
(Guide)Standard Guide for Microspectrophotometry in Forensic Paint Analysis
Standard Guide for Microspectrophotometry in Forensic Paint Analysis
SIGNIFICANCE AND USE
5.1 This guide is designed to assist an analyst in the selection of appropriate sample preparation methods and instrumental parameters for the analysis and comparison of paint pigments and colors. When used for comparison purposes, the goal is to determine whether any exclusionary differences exist between the samples.
5.2 Paint sample spectra can be measured by reflectance or transmittance spectroscopy for comparison purposes. Transmittance measurements are generally preferred and are required for the analysis of UV absorbers in clear coats and the detailed analysis of effect pigments that are not opaque. Emission comparison by means of fluorescence is also measurable.
5.3 It is not the intention of this guide to present comprehensive theories and methods of MSP. It is necessary that the analyst have an understanding of UV-Vis-NIR MSP and general concepts of specimen preparation before using this guide. This information is available from manufacturers’ reference materials, training courses, and references such as Eyring (1),3 Stoecklein (2), and Purcell (3).
SCOPE
1.1 This guide is intended to assist forensic analysts who conduct UV, visible, NIR, or fluorescence emission spectral analyses on small fragments of paint or use Guide E1610, as this guide is to be used in conjunction with a broader analytical scheme.
1.2 This guide deals primarily with color measurements within the visible spectral range but will also include some details concerning measurements in the UV and NIR spectral ranges. The particular method(s) employed by each analyst depends upon available equipment, examiner training (Practices E2917, E3234), sample suitability, and sample size.
1.3 This guide provides basic recommendations and information about microspectrophotometers.
1.4 This guide does not address other areas of color evaluation such as colorimetric values, paint surface texture or pigment particle size, shape, or dispersion within a paint film that are evaluated by other forms of microscopy.
1.5 This guide is directed at the color analysis of commercially prepared paints and coatings. It does not address the analysis or determination of provenance of artistic, historical, or restorative paints, but it could be useful in those fields.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (see Practices E2917, E3234), and demonstrated proficiency to perform forensic casework.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2808 − 21a An American National Standard
Standard Guide for
1
Microspectrophotometry in Forensic Paint Analysis
This standard is issued under the fixed designation E2808; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Color is one of the most important comparative characteristics of paints. The comparison of color
isoneofthefirststepstakeninaforensicpaintcomparison.Subjectivetermssuchas“blue,”“violet,”
or“purple”aredescriptorsofcolorbutareinadequateforclearcommunicationofcolorastermscould
suggest different colors to different people. It is essential to note that this guide does not propose the
use of instrumental color comparison for objects that are distinguishable to the eye. Since the 1940s,
analytical instruments have been able to discriminate colors that the average human eye cannot
distinguish. Microspectrophotometers (MSPs), in particular, allow for an objective measurement of
thecolorofsmall,millimetreorsubmillimetresamplesandaregenerallymoresensitivethanthemore
subjective results of visual microscopical color comparisons.
Suitableinstrumentswithappropriateoptics,sensitivity,resolution,anddynamicrangecanmeasure
spectral curves from small samples as that light is transmitted, absorbed, reflected, or emitted (by
means of fluorescence) by the sample. The spectral limits of different instruments can vary and can
extend from the ultraviolet (UV) (~190 to 380 nm) through the visible spectral region (~380 to 780
nm) to the near infrared region (NIR) (~780 to 2500 nm). MSPs should not be confused with
broadband or absorption filter-based tristimulus systems.
1. Scope 1.4 This guide does not address other areas of color evalu-
ation such as colorimetric values, paint surface texture or
1.1 This guide is intended to assist forensic analysts who
pigment particle size, shape, or dispersion within a paint film
conduct UV, visible, NIR, or fluorescence emission spectral
that are evaluated by other forms of microscopy.
analyses on small fragments of paint or use Guide E1610,as
thisguideistobeusedinconjunctionwithabroaderanalytical 1.5 This guide is directed at the color analysis of commer-
scheme. cially prepared paints and coatings. It does not address the
analysis or determination of provenance of artistic, historical,
1.2 This guide deals primarily with color measurements
or restorative paints, but it could be useful in those fields.
within the visible spectral range but will also include some
details concerning measurements in the UV and NIR spectral 1.6 The values stated in SI units are to be regarded as
ranges. The particular method(s) employed by each analyst standard. No other units of measurement are included in this
depends upon available equipment, examiner training (Prac- standard.
tices E2917, E3234), sample suitability, and sample size.
1.7 This standard is intended for use by competent forensic
1.3 This guide provides basic recommendations and infor- science practitioners with the requisite formal education,
mation about microspectrophotometers. discipline-specific training (see Practices E2917, E3234), and
demonstrated proficiency to perform forensic casework.
1.8 This standard does not purport to address all of the
1
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
safety concerns, if any, associated with its use. It is the
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
responsibility of the user of this standard to establish appro-
Current edition approved Sept. 1, 2021. Published September 2021. Originally
priate safety, health, and environmental practices and deter-
approved in 2011. Last previous edition approved in 2021 as E2808 – 21. DOI:
10.1520/E2808-21A. mine the applicability of regulatory limitations prior to use.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E2808 − 21a
1.9 This international standard was developed in accor- 3.2.4.1 Discussion—These maxima and minima vary in
dance with internationally recognized principles on standard- position with wavelength. This allows radiation of any given
ization established in the Decision on Principles for the wavelength to be isolated from a mixture of wavelengths (for
Development of International Standards, Guides and Recom- example, white light) and allows the grating to be us
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2808 − 21 E2808 − 21a
Standard Guide for
1
Microspectrophotometry in Forensic Paint Analysis
This standard is issued under the fixed designation E2808; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Color is one of the most important comparative characteristics of paints. The comparison of color
is one of the first steps taken in a forensic paint comparison. Subjective terms such as “blue,” “violet,”
or “purple” are descriptors of color but are inadequate for clear communication of color as terms could
suggest different colors to different people. It is essential to note that this guide does not propose the
use of instrumental color comparison for objects that are distinguishable to the eye. Since the 1940s,
analytical instruments have been able to discriminate colors that the average human eye cannot
distinguish. Microspectrophotometers (MSPs), in particular, allow for an objective measurement of
the color of small, millimetre or submillimetre samples and are generally more sensitive than the more
subjective results of visual microscopical color comparisons.
Suitable instruments with appropriate optics, sensitivity, resolution, and dynamic range can measure
spectral curves from small samples as that light is transmitted, absorbed, reflected, or emitted (by
means of fluorescence) by the sample. The spectral limits of different instruments can vary and can
extend from the ultraviolet (UV) (~190 to 380 nm) through the visible spectral region (~380 to 780
nm) to the near infrared region (NIR) (~780 to 2500 nm). MSPs should not be confused with
broadband or absorption filter-based tristimulus systems.
1. Scope
1.1 This guide is intended to assist forensic analysts who conduct UV, visible, NIR, or fluorescence emission spectral analyses on
small fragments of paint or use Guide E1610, as this guide is to be used in conjunction with a broader analytical scheme.
1.2 This guide deals primarily with color measurements within the visible spectral range but will also include some details
concerning measurements in the UV and NIR spectral ranges. The particular method(s) employed by each analyst depends upon
available equipment, examiner training (Practices E2917, E3234), sample suitability, and sample size.
1.3 This guide provides basic recommendations and information about microspectrophotometers.
1.4 This guide does not address other areas of color evaluation such as colorimetric values, paint surface texture or pigment
particle size, shape, or dispersion within a paint film that are evaluated by other forms of microscopy.
1.5 This guide is directed at the color analysis of commercially prepared paints and coatings. It does not address the analysis or
determination of provenance of artistic, historical, or restorative paints, but it could be useful in those fields.
1
This guide is under the jurisdiction of ASTM Committee E30 on Forensic Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved March 1, 2021Sept. 1, 2021. Published April 2021September 2021. Originally approved in 2011. Last previous edition approved in 20192021
ɛ1
as E2808 – 1921. . DOI: 10.1520/E2808-21.10.1520/E2808-21A.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E2808 − 21a
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard is intended for use by competent forensic science practitioners with the requisite formal education,
discipline-specific training (see Practices E2917, E3234), and demonstrated proficiency to perform forensic casework.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
2
---------------------- Page: 2 ----------------------
E2808 − 21a
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the
...
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