Effect of hydrophilic and hydrophobic treatments on bloodstain patterns of drip stains on knitted cotton and polyester fabrics

Abstract

ABSTRACT Textiles are one of the most frequently collected items at crime scenes. Even so, the mechanisms that create bloodstains on textiles are not well understood. This is likely due to the wide range of textiles and the many surface treatments given to them to enhance their performance. In this study, the final appearance of 50 μl passive drip stains on four in-house knitted apparel textiles (scoured cotton, hydrophobic cotton, hydrophilic polyester and hydrophobic polyester) was investigated. The yarns used to make the knits were 167 dTex polyester filament and 342 dTex cotton staple yarns. They were knitted on the same knitting machine under nominally identical conditions. The area of bloodstains on the scoured cotton knit fabrics was 46 mm2 and 30 mm2 on the hydrophobic cotton. i.e. the stains on the hydrophilic cotton were 50% larger than on the hydrophobic cotton. The bloodstains on hydrophobic polyester were only 15.6 mm2, but were 242 mm2 on hydrophilic polyester, i.e. 15 times larger. The stain areas on the polyester were both smaller (hydrophobic finish) and larger (hydrophilic finish) than on the cotton fabrics. It is shown that these typical chemical treatments play a much more important role on bloodstain areas than fibre type or fabric construction.