• What is pilling
Pilling is a physical process that occurs on the surface of fabrics and leads to the formation of irregular clumps of fibers ranging from small to large, named “pills”, more or less anchored to the surface of the fabric.
The phenomenon mostly affects textiles made with short fibers.
• Why it forms
Pilling is caused by mechanical solicitation of the fibers in the textile which basically ensues from the rubbing and/or pressing action by outside agents, together with the friction that occurs between fibers. In general terms, the rubbing causes fibers to be released from the weave and rise to the surface where they get tangled with others forming knots that become pills as they grow larger.
The propensity of a fabric to form pills is strictly tied to:
average length of the fibers
type of yarn (gauge and number of twists)
weave coverage factor
treatments and finishes.
• How pilling is measured
The degree of pilling of a fabric is measured on a scale from 1 (worse result) to 5 (best result) using mid-way points. The pilling value is assigned considering the number and size of the pills, fuzz on the surface of the fabric and its general change in appearance.
• How pilling propensity is determined
Labs can use two different instruments to assess the pilling propensity of a fabric. The results obtained with each of the two can differ due to their exercising a different type of rubbing action.
1. Martindale Wear and Abrasion Tester (according to UNI EN ISO 12945-2 and ASTM D4970 standards)
This instrument makes each of the 6 stations undergo a specific rotation cycle by which areas of the fabric are made to rub against each other with even force.
The result is then evaluated after a suitable number of rubbing cycles (usually ranging from 1,000 to 7,000 cycles). This instrument simulates localized wear, akin to that undergone by the armpits and sides of a garment.
2. ICI Pilling Box Tester (according to UNI EN ISO 12945-1 and IWS TM 152 standards)
This instrument consists of 2 boxes internally lined with a specific abrasive material (cork), which accommodates 4 supports covered with the fabric to be tested.
The box is made to rotate (generally 14,400 cycles), hence causing the textile specimens to rub against each other and the wall.
The ICI Pilling box tester simulates the garment overall wear, especially in those areas (back, abdomen and leg) less subject to localized friction.