Photofading of Black Dyes in Cotton and Polyester Fibers Resulting from Environmental Exposure to Sunlight
Date of Submission
Virginia M. Maxwell, D.Phil.
Photofading, Degradation, Black Cotton and Polyester Fibers, Sunlight
Cotton textiles, Polyester fibers, Dyes and dyeing--Textile fibers, Sunshine, Environmental degradation
Color is one of the most important properties analyzed during forensic fiber examinations due to its discriminatory power. Differing colors in fibers are usually sufficient grounds for exclusion, but in cases where a lengthy period has passed between crime commission and evidence recovery, the high probability of environmental degradation having altered the questioned fibers’ properties could lead to false exclusions. Photofading, the loss of color resulting from exposure to light, is a common form of degradation observed in fibers. Although well-known in the dyeing industry, it is not typically factored into forensic fiber examinations. Published photofading research has been limited to idealized simulations involving dye solutions rather than dyed textiles, and studies with dyed textiles have focused on cellulosic fibers and non-black dyes despite the prevalence of manufactured and black fibers.
This study investigated photofading in black cotton and polyester fibers that were exposed to sunlight in various environments over a 3.5-month period. The objective was to determine how fiber type and environmental conditions impacted the rate of photofading. Results of a control experiment indicated that photofading rates were dependent on the strength of fiber-dye interactions (which is predicated on the chemical properties of both) rather than fiber type alone. Due to the outbreak of COVID-19 during the later stages of research, results for the environmental exposure experiment were unable to be gathered. A discussion of the expected results is presented instead, along with possibilities for future photofading studies and the greater forensic implications that such work may have.
Mahaney, Maggie E., "Photofading of Black Dyes in Cotton and Polyester Fibers Resulting from Environmental Exposure to Sunlight" (2020). Honors Theses. 35.