The Reason Your Favorite Textiles Probably Feel Like They Do

It’s not rocket science. It’s material science.

There’s one thing that nearly everyone has: a favorite cotton t-shirt. It may have holes and stains all over it, but it feels so soft, and has been with you for so many years, that you can’t let it go.

Part of the reason this t-shirt is likely your favorite has a lot to do with the length of the cotton fiber it’s made out of. During the development phase for our bed sheets, we spent a lot of time visiting farms and examining the material properties of cotton. We found that a short fiber will often create a scratchy and weak textile, while a long fiber is the key ingredient in some of the most durable, and softest, textiles you can find.

The label “100% cotton” barely scratches the surface. A textile is woven out of yarn and yarn is woven out of fibers. Short cotton fibers are generally less expensive, but don’t lay flat as they’re wrapped around each other. This actually looks like grass on a microscopic level, and the resulting textile often feels scratchy. Instead, a long fiber will create a smooth and strong yarn that gets even softer over time. It’s the best natural ingredient.

One big key is the species of cotton. The big four families that are grown commercially are Asiatic, Upland, Egyptian, and Pima cotton. Asiatic cotton is native to India and is a short fiber cotton. Upland is medium-length, and it’s found in a lot of cotton products. Egyptian cotton is a long cotton fiber. Pima is one of the longest cotton fibers in the world. The four different families, sub-varieties, and climate all wind up affecting the properties of the cotton and ultimately the textiles they’re woven into.

Sometimes, manufacturers try to mask the natural properties of cotton they’re using. During our research, we noticed that some t-shirts, bed sheets, and other textiles no longer feel soft after a few washes. It’s because manufacturers sometimes add chemical finishings, e.g., silicone, to textiles in order to mask underlying scratchiness and help them feel soft. The problem, however, is that these finishings wear or wash off quickly. A lot of boxed-in-the-garage tees may have had a lot of chemicals on them to begin with.

It can be hard to sort through the choices. One easy way to better predict how a textile will wear is to look at the brand of cotton used in it. American Pima, for example, is 35% longer than standard cottons, and Supima is a branded version of Pima that can be traced directly back to its source, with much of it coming from a farm in central California. It’s the one we ended up selecting for the the Casper sheets, and along with Egyptian cotton, is one of the longest cotton fibers in the world.

When it comes to cotton fibers, longer really is better.