Analysis of Metameric Blue Fibers and Their Forensic Significance

• NCJ Number: 227705
• Journal: Journal of Forensic Sciences Volume: 54 Issue: 4 Dated: July 2009 Pages: 841-845
• Author(s): Mary Eng B.Sc.; Paul Martin Ph.D.; Candida Bhagwandin B.Sc.
• Date Published: July 2009
• Length: 5 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

Metameric samples of blue textile fibers (phenomenon of two or more colored items produced using different dyes, pigments, or coloring agents that appear to be the same color under specific lighting conditions), which were created using different coloring agents or different relative concentrations of the coloring agents, were studied in order to show that they could be differentiated by obtaining their spectra between 350 and 800 nm, using ultra-violent (UV)-visible microspectrophotometry.

Abstract

Metameric samples created using different coloring agents were easily differentiated through their UV-visible-NIR absorbance spectra. The absorbance spectra will have different shapes, representing differences in absorbance at different wavelengths. In this scenario, it should be easy to observe that the samples are from different sources. Metameric samples created by using the same coloring agents in different proportions can be differentiated through their UV-visible absorbance spectra if there are significant differences in the formulations. The absorbance spectra will have similar, although not identical shapes because of different relative peak heights. The differences in peak heights correspond to the difference in dye stuff concentrations. In this scenario, the samples can be determined to be from different sources if there are significant differences in the proportions of the coloring agents. Contrary to published literature, the spectra of mesmeric samples do not necessarily intersect at three or more loci. Some spectra do not intersect at all. The dye combinations and concentrations were chosen to achieve metamerism between the fabric swatches under Illuminant D65 (daylight) lighting conditions. The dye types were chosen based on their suitability for the fiber type. The cotton and polyester swatches are examples of mesmeric pairs created using different coloring agents. The nylon, silk, and wool swatches are examples of mesmeric pairs created using the same coloring agents, but in different proportions. 3 tables, 6 figures, and 7 references