Pilling happens when excess colored pencil material gathers into small, waxy clumps on the surface of the paper.
It’s a common characteristic of pencils with a high percentage of wax in the formula but it can happen with oil intense pencils too.
Pilling usually happens when the paper tooth can no longer accept additional pencil material, but the artist continues applying color.
Heavy pressure, repeated layering, and excessive burnishing can encourage pilling.
Unlike shedding, which produces loose dust or fine particles, pills are larger, cohesive clumps of pigment and binder that may stick to the artwork. Many artists use the point of a craft knife to remove pills as they color.
Some pilling is normal, even with high-quality colored pencils. It is not a sign of poor pencil quality, but often indicates that the surface has reached its capacity to hold additional material.
Pilling here refers to the accumulation of colored pencil clumps, not the damage of paper fibers, which is also commonly called paper pilling.