No matter how hard you try, your pillowcases cannot stay white forever. Over time they begin to fade and turn shades of grayish yellow or yellow. The color change is due to a natural progression in age, wear and tear. While you can’t completely eliminate the causes, you can prevent the process from moving quickly, therefore extending the life of the pillowcase.
A person’s sweat can turn a pillowcase yellow. Perspiration is used to maintain body temperature. Sweat is the result of perspiration and is the secretion of oils from the sweat glands. These oils seep into the fabric of the pillowcase and stain the fabric when the oil dries.
Two occurrences found in nature lead to yellowing: direct sunlight and oxidation. Direct sunlight over time breaks down a protective whitening agent found in the fabric. Once the whitening agent breaks down, the actual color of the fabric is exposed. This color appears yellowish compared to the white coloration created by the chemical agent. Oxidation is the result of fibers in the fabric becoming exposed to direct oxygen. The air contains contaminants that eventually turn the fabric fiber to a gray or yellow. Time and maintenance also take a toll, as chemicals in detergents break down the fabric and build up within it. A disadvantage with line drying linens compared to machine drying them is the linen is exposed to both oxidation and direct sunlight. This brings a faster occurrence of yellowing, although machine drying breaks down the fabric in the tumbling process.
One method to extend the color of pillowcases is proper maintenance. Using insufficient amounts of detergent, the wrong water temperature or too little rinsing after washing causes buildup in the material. Washing pillowcases with a light-duty detergent in cold water helps prevent yellowing. Using a color-safe bleach alternative helps prevent yellowing. Avoid dry cleaning too often, as the process uses harsh chemical detergents that can speed up the aging of the linen.
Keep the pillowcases out of direct sunlight. Store extra pillowcases and exchange them with ones being used after each wash to extend their life.
Yellowing pillowcases are treatable when washed in hot water using the permanent press cycle. Replace detergent with a cup of water conditioner while using a cool rinse cycle. Use an all-fabric bleach with the same process should yellowing persist.
Heirloom or antique pillowcases should never be machine washed. According to both "Vintage Indie" magazine's Elizabeth Holcombe and antiques expert Christopher Kent, the rinse and spin cycles are too harsh for the aged fabric; the result would be torn linen. Silk is another fabric that cannot be machine washed to remove stains. Wash delicate and aged fabric by hand. Holcombe suggests soaking linens in two gallons of cold water with 1 cup white vinegar over several hours. The water will turn yellow, indicating the fabric is being cleaned.