Why Do Cotton Sheets Pill?

Natural cotton fabric breathes and is more comfortable to sleep on than synthetics, and 100 percent cotton sheets are a good bedding investment. But pilling can offset the cotton sheet benefits you paid good money for. Buy smart -- with careful attention to yarn length, thread count, weaving style, cleaning and care to prevent pilling and keep your sheets looking and feeling new.

What Is Pilling?

When a cotton thread breaks or comes unraveled from a weave, the raw end frays, tangles, knots up and becomes a tiny ball, or pill. The bumpy broken place is unsightly and uncomfortable and will shorten the life of your sheets.

Common Causes of Pilling

Staple Length

Staple length can increase or decrease a sheet's tendency to pill. The extra-long-staples -- ELS -- of Egyptian cotton, pima and Supima cotton sheets are softer, stronger and less apt to pill than shorter staples. Shorter cotton threads have more loose ends to weave into the fiber, and they work free more easily. Shorter staple cotton is also weaker than the longer threads and breaks more readily. So, smooth longevity is one reason ELS cotton sheets come with premium prices, but they should last longer than less expensive, shorter staple sheets.

Weave Style

Weave makes a difference. A looser weave tends to pill; a tight weave withstands stress and resists pilling. High quality cotton sheets are made with tightly woven strands and high thread counts. That means more vertical and horizontal threads per square inch of fabric -- anything over 400 thread count is high quality, but sheets in the 200 to 400 thread count range are fine. The type of weave matters, too. Percale is a plain tight weave with a thread count of at least 180, but often higher. It feels crisp, is durable and resists pilling. Sateen is a soft fabric with more vertical than horizontal threads and is more prone to pilling.

Blends

Pure cotton is a tough fiber that takes some abuse before it loses elasticity and breaks. Blended fabric sheets may not require ironing, but the polyester in a blend may shrink in the dryer, causing pills; nylon threads in a blended fabric won't shrink or break, but the cotton threads in the blend will. Over time, the blend creates tension that weakens the cotton. In general, cotton blends do not have the comfort or staying power of 100 percent cotton sheets.

Fitted Sheets

Fitted sheets are elasticized to fit snugly on a mattress, creating constant stress on the fabric. Add the weight of a sleeping body, and night-long tossing and turning, and it's no wonder the sheets develop pills and wear out faster than their matching flat sheets.

Laundry Pill-Proofing

Correct care minimizes the chance of pilling and extends the life of your sheets. Heat causes cotton fibers to become brittle over time, destroying their elasticity. Chlorine damages cotton fibers, leading to their eventual breakage. Short wash cycles, gentle detergents, cool dryers or line-drying, no ironing or low-heat irons, and bleach avoidance preserve the strength of sheet threads so they don't break, tangle, knot and form pills. Overfilling the washer, and washing and drying sheets with rougher fabrics -- denim, for instance -- can cause abrasion and break cotton fibers.