How come linen wrinkles so much more than other fabrics?
How come linen wrinkles so much more than other fabrics? asks Andi, via email.
Linen is probably the oldest fabric, with bits and pieces dated to 8,000 BC. It is also the most wrinkle-prone fabric. (So along with food, furniture, and jewelry, linen-wrapped Egyptian mummies also carried their creases into eternity.)
Linen is made from the fibers of the flax plant, the plant that gives us flax seeds and oil. Fabric made of linen is cooling in hot months, since can absorb up to 20 percent of its weight in moisture, without feeling especially damp. Linen is also incredibly strong, resisting stretching.
Both linen and cotton, as well as rayon, are made from cellulose, the basic structural component of green plants. Cellulose is a polymer, a supermolecule made of many smaller molecules linked together in a long, straight chain. The smaller molecules are made from the sugar called glucose. (We can’t digest the sugars in cellulose fiber, but cows can, and do.) Side-by-side cellulose chains link up using hydrogen bonds, in much the same way water molecules cling together. The bonds give a cellulose-based fabric its “tensile strength.”
Water molecules easily bond to the molecules in cellulose, and that can create problems. Splash water on an untreated linen or cotton shirt, and H2O molecules insinuate themselves into the polymer chains, swelling the fibers and destabilizing the existing bonds. As the fabric dries, new bonds form. The rearranged chains leave the shirt with stubborn wrinkles, creases that match how the fabric was folded as it dried. Heat accelerates the process, quickly shrinking the water-swollen fibers and setting in wrinkles.
While both heat and water cause wrinkles, they can also undo them. It’s virtually impossible to get the wrinkles out of a bone-dry cotton or linen shirt with a dry, warm iron. But wetting or steaming the shirt first and using a very hot iron (or a hand-held steamer) can do the trick. How come? According to chemists, adding water swells the fabric fibers, breaking the hydrogen bonds that created the shirt’s annoying creases. Heat speeds the process. As bonds re-form in new places, the fabric cools into a smooth expanse.
Because linen absorbs water so easily, and is also not very elastic, it tends to form sharp creases as it dries. In fact, with repeated creasing, linen fibers may actually wear and break along the folds.
The quest for “permanent press” clothing has led chemists to develop many different chemical pretreatments, most based on formaldehyde, a chemical preservative. Formaldehyde compounds stabilize the hydrogen bonds between molecular chains, making a fabric water- and wrinkle-resistant.
However, formaldehyde is a known skin, eye, and lung irritant, and the amount found in clothing — even in clothing not marked as “wrinkle-free”- varies by manufacturer and country of origin. Washing before wearing is always a good idea, but will not remove all formaldehyde-based chemicals from the body of the fabric. Fabrics certified as “organic” should be formadehyde-free. To reduce wrinkles (and ironing time) in untreated fabrics, remove clothes from the dryer as soon as they’re dry, and hang immediately.
