Pilling can be defined as fiber bundles collected on the surface of the fabric by friction effect. In the structure of the beads, there are generally foreign substances. This deteriorates the appearance of the fabric and leads to undesirable situations.

Hydrophobic fibers, or polyester fibers, are electro-static and attract more impurities than hydrophilic fibers, ie viscose, cotton and wool fibers. Hydrophobic fibers have higher tensile and flexural strength and abrasion resistance. Hydrophilic fibers are fibers with low breaking and abrasion resistance. Therefore, they leave the fabric surface by friction more easily than synthetic fibers.

Pile formation is the first stage of pilling. The first signs of wear on the fabric surface start with the formation of pile. Pilling occurs when the free fiber ends that are not in the yarn structure are exposed. If the frictional force exceeds the reaction force generated by entangling the fibers between the yarns, pilling occurs. Weak fibers quickly cope while forming a shorter but more dense pile layer. The next step is that the pile becomes complex and begins to form beads.

Numerous test methods are available to measure the pilling tendency of fabrics. Pilling measurement and evaluation methods are mainly based on either rounding of the sample or abrasion of the sample.

Pilling tests carried out by authorized laboratories using Random Tumble Pilling Tester devices are based on the following standards:

• TS EN ISO 12945-3 Textile - Determination of the susceptibility of surface pilling, feathering and dulling of fabrics - Part 3: Imitation free fall pilling method
• ASTM D3512 Standard test method for pilling strength and other related surface changes in textile fabrics: Tumble free fall pilling method

In order to achieve high quality and reliable results, laboratories have to have a solid infrastructure and a strong staff.