Abstract: A process for marking a textile product by means of an invisible substance whose presence in the textile product is detectable by conventional detection methods of analytical chemistry, wherein the substance for marking the textile product is so selected as to be suitable for extraction from the textile product and detection through application of an absorbent probe.

Abstract: A process of making a low-shrinkage, air-textured yarn, in particular sewing yarn, of synthetic, pre-oriented polymer multifilaments, includes the steps of drawing multifilaments in the form of a single strand at a temperature of about 180.degree. to 230.degree. C. by a factor of 1.6 to 2.5, air-texturing the drawn strand at a rate of overfeed of 1.03 to 1.20 to form a single-strand raw yarn, feeding the raw yarn to a fluffing zone of predetermined length at a rate of overfeed of 1.003 to 1.025, winding the fluffy raw yarn at slightest possible tension, reeling off and twisting the wound raw yarn, and treating the twisted raw yarn at a temperature of 125.degree. to 135.degree. C. over 1 to 3 hours in a dyeing unit, and, optionally, dyeing the raw yarn. The process is equally applicable for making plied yarns.