Most people choose socks by feel, and the feel comes from the fiber. Over the last few years, two fibers have shown up on more and more sock labels: rayon and modal. Both come from wood pulp, both feel soft, and they are often treated as the same thing. In a sock, they do not wear the same.
Modal is one of the three fibers in our socks, so I spent a long time with this question. Here is what I learned.
What rayon and modal have in common
Rayon and modal are both made from cellulose, the material that gives plants their structure. The cellulose is dissolved, then pushed through fine openings to form new fibers. Because they start from a natural material but go through a chemical process, they are usually called semisynthetic or regenerated fibers.
Both are soft, both drape well, and both absorb moisture readily, which is why they feel cooler against the skin than most synthetics.
Modal vs rayon: what sets them apart
Modal is a type of rayon. The difference is in how it is made. Standard rayon, often labeled viscose, is soft but loses a good deal of its strength when wet. That matters in a sock, which is damp for much of the day and goes through the wash every time you wear it. Viscose socks tend to stretch out, pill and thin at the heel sooner than you would like.
Modal is processed to keep more of its strength when wet. Lenzing Modal, the version in our socks, is made from beech wood pulp. In practice, modal holds its shape better, shrinks less and keeps its softness through more washes than standard rayon.
| Rayon (viscose) | Modal | |
|---|---|---|
| Source | Wood pulp, sometimes bamboo | Wood pulp, usually beech |
| Feel | Soft, silky | Soft, smooth |
| Strength when wet | Lower | Higher |
| Shape after washing | Stretches and shrinks more | Holds its shape better |
| Moisture | Absorbs well | Absorbs well |
What about bamboo?
Many socks are sold as bamboo. In most cases the fiber is rayon made from bamboo: the bamboo is dissolved into cellulose and spun the same way as any other rayon. In the United States, the Federal Trade Commission requires it to be labeled as rayon or viscose made from bamboo rather than simply bamboo. Claims that the finished fabric keeps natural antibacterial properties from the plant are not well supported, because the processing breaks the plant down completely.
That does not make bamboo rayon a bad fabric. It is still soft and breathable. It is just rayon, with the same strengths and the same weakness when wet.
Why the blend matters as much as the fiber
A sock made only of rayon or modal would feel lovely for a week and then lose its shape. Almost every soft sock is a blend, and the other fibers in the blend decide how it fits and how long it lasts.
Spandex is what lets a sock stretch over your foot and spring back. Without it, a sock bags out after a few hours. Nylon is common too, especially in athletic socks, because it adds strength in the areas that take the most wear. Cotton adds structure and breathability and keeps a sock from feeling slippery.
Ours is 45% cotton, 45% Lenzing Modal and 10% spandex. The modal gives the softness and moves moisture away from the skin. The cotton gives the fabric body, so it sits flat inside a shoe instead of sliding around. The spandex lets the sock recover its shape after every wear, which matters most in a no show sock, where the fit at the heel is what keeps it on.
How fiber affects a no show sock
The fiber question matters more in a no show sock than in almost any other kind. A no show has no cuff to hold it up, so it relies entirely on how well it fits at the heel. Any fabric that relaxes, stretches out or thins with washing will slip sooner.
That is also why we cut and sew our socks from fabric instead of knitting them as a tube. The heel is shaped to the back of the foot, and the silicone grip inside it holds a heel that already fits. A soft fiber that keeps its shape is half of that. The construction is the other half.
The sustainability question
Rayon and modal come from trees, which are renewable, and that is a real advantage over fibers made from oil, such as polyester and nylon. It is not the whole picture. Turning wood into fiber is a chemical process, and how responsibly it is done varies a lot between producers. That is one reason we chose Lenzing Modal rather than unbranded modal or viscose: the source and the process are traceable.
The other side of sustainability is simply how long a sock lasts. A pair that keeps its shape for many months instead of a few weeks means fewer socks bought and thrown away.
How to choose soft socks
Read the label. Look for modal rather than plain rayon or viscose if you want a soft sock that lasts, and look for a blend with some spandex so it keeps its shape. Treat bamboo as rayon, because that is what it is.
Think about where you will wear them. For running and training, a sock built for that activity, often with nylon, is the right tool. For everyday shoes, softness, breathability and a fit that holds matter most. If the sock is a no show, check how the heel is made.
Finally, wash them gently. Machine wash cold and tumble dry low. High heat is hard on spandex and on cellulose fibers alike.
Frequently asked questions
Is modal the same as rayon?
Modal is a type of rayon. Both are made from wood pulp, but modal is processed to keep more of its strength when wet, so it holds its shape and softness better through washing.
Is modal better than cotton for socks?
They do different jobs. Modal is softer and smoother and handles moisture well. Cotton gives more structure and breathability. Blended together, as in our socks, you get the softness of one and the body of the other.
Are bamboo socks really bamboo?
Most are rayon made from bamboo pulp. The plant is broken down completely during processing, so the fabric behaves like any other rayon.
Do modal socks shrink?
Modal shrinks less than standard rayon. Washing cold and drying on low heat keeps shrinkage to a minimum.
Why do soft socks need spandex?
Soft fibers alone stretch out. A small amount of spandex lets the sock spring back to its shape, which keeps it fitting well through the day and through many washes.
The bottom line
Rayon and modal both make soft socks, but modal keeps its strength when wet, so it holds its shape and softness far longer. The blend matters as much as the fiber. A little spandex keeps the fit, and cotton gives the fabric body. When you read a sock label, look for modal, look for stretch, and treat bamboo as the rayon it is.