Chemical contamination on fibers, yarns, and fabrics is a problem commonly encountered in the textile industry. Infrared spectroscopy has been used to identify chemical contaminants on textile materials by either extracting a contaminated material with an organic solvent and analyzing the extract or by applying a spectral subtraction technique. However, the existence of a mixture of chemicals on textile materials makes it difficult to determine the exact nature of contaminants using those methods. In this research, we extracted a contaminated 100% rayon yarn using one polar solvent and one nonpolar solvent. By subtracting the infrared spectrum of the nonpolar solvent extract from the spectrum of the polar solvent extract, we identified ethylene terephthalate oligomer as a polar chemical contaminant on the yarn.