How to Wash a Wool Sauna Hat Without Shrinking It

Boiled wool is made by doing on purpose exactly what you want to avoid in the laundry: soaking wool in hot water and working it until the fibers lock together. So if you toss a wool sauna hat into a hot, busy wash, the process simply continues and the hat comes out smaller and stiffer. The good news is that a wool hat rarely needs washing at all, and when it does, the routine below takes about 20 minutes plus drying time.

Key takeaways

1. Most of the time, airing it out is enough.
2. Heat plus rubbing is what shrinks wool.
3. Hand wash in cold water, gently.
4. Use a real wool detergent.
5. Dry it flat, away from heat and sun.
6. Store it clean to keep moths away.

1. Most of the time, airing it out is enough

Wool is naturally resistant to odors and stains, which is why it needs less washing than most fabrics, according to the Woolmark Company. For a sauna hat that means a simple routine after every visit: take it out of your bag as soon as you get home, shake it out and let it dry in a place with good airflow. Laying it flat on a towel or over a chair back works fine. Woolmark suggests laying wool flat on a bed or towel for about an hour to get rid of smells like smoke or food, and the same idea works for a hat that smells of sauna. What you should not do is leave a damp hat rolled up in a gym bag overnight. Wool can absorb a lot of moisture, and it needs air to let it go again. Wash only when the hat looks dirty or still smells after airing.

2. Heat plus rubbing is what shrinks wool

Each wool fiber is covered in tiny scales, a bit like roof shingles. A guide from the University of Wisconsin Extension explains what happens in hot water: the scales lift, and when the fibers rub against each other, they hook together and fuse. That is felting, and it is permanent. Fabric makers use it deliberately. Britannica describes fulling, the process behind boiled wool, as exposing wool fabric to moisture, heat, friction and pressure until it shrinks by 10 to 25 percent. Your hat already went through that once, which is why it feels dense and soft. A second round in a hot washing machine keeps going in the same direction. The three things to avoid are:

• Hot water and sudden changes in temperature.
• Rubbing, scrubbing and wringing.
• Long, hard spin cycles.

3. Hand wash in cold water, gently

For our sauna hats we recommend hand washing in cold water. Woolmark's general advice for wool garments is lukewarm water of about 86°F (30°C) and a short soak, then rinsing that ends in cold water. Cold all the way through is the safer choice for a hat you want to keep its exact size. Here is how:

• Fill a sink or bowl with cold water and dissolve a little wool detergent in it.
• Turn the hat inside out and push it under the water.
• Let it soak for about 10 minutes, the time Woolmark suggests.
• Squeeze the suds through the hat gently with your hands. Do not rub the fabric against itself.
• Drain, refill with cold water and rinse the same way until no foam is left.
• Press out the water between your palms. Do not twist or wring it.

4. Use a real wool detergent

Regular laundry detergent is made to get grass stains out of jeans, not to go easy on a protein fiber. Wool is made of keratin, the same type of protein as your own hair. Woolmark recommends a mild detergent with a relatively neutral pH and advises against heavy duty detergents, bio detergents that contain enzymes, and anything with bleach. It is also clear that you should never use bleach on wool, whether chlorine or oxygen based. A few more tips from the same guide:

• If your detergent is a powder, dissolve it completely before the hat goes in. Undissolved grains can leave spots.
• Skip fabric softener, or use very little. Woolmark notes that softeners act as a lubricant and too much can cause pilling.
• Follow the dosage on the bottle. More soap only means more rinsing.

Any detergent sold for wool or delicates will do the job.

5. Dry it flat, away from heat and sun

After pressing out the water, roll the hat in a dry towel and press down to soak up more moisture. Then lay it flat on a fresh towel to dry. Woolmark recommends drying knitwear flat whenever possible and gently shaping it while it is still damp. Its other rules apply to your hat too:

• No direct sunlight, and not right next to a sunny window.
• Never on a radiator or another direct heat source.
• No clothes dryer. The heat and tumbling are exactly the felting conditions described above.
• Do not hang it on a hook while it is heavy with water, it can stretch.

Shape the Original into its flat form, and smooth the brim of the Pro so it dries in place. Depending on the room, this can take a day or so. Do not wear it until it is completely dry.

6. Store it clean to keep moths away

Clothes moth larvae eat wool. The University of California's pest management program notes that fabrics with food, sweat or urine stains are more likely to be damaged, and that insects are less likely to feed on clean fabrics than on heavily soiled ones. A sauna hat soaks up sweat, so it is worth storing it clean and dry, especially over a long summer break. The UC guide recommends:

• Clean, dry items in an airtight container.
• Not relying on cedar alone. Its effect is debatable and fades over the years.
• Hanging woolens in the sun now and then and brushing them, because larvae dislike bright light.
• If you suspect moths, sealing the item in a plastic bag and freezing it for several days below 18°F (about minus 8°C).

FAQ

Can I put my wool sauna hat in the washing machine?

We do not recommend it. Even a wool cycle adds movement, and movement plus water is what makes boiled wool felt and shrink. Hand washing in cold water takes only a few minutes.

How often should I wash a sauna hat?

Rarely. If you air it out after every visit, you may only need to wash it a few times a year, or when it looks dirty or the smell does not go away after airing.

My sauna hat shrank in the wash. Can I fix it?

Usually not completely. Once the wool fibers have locked together, the felting is permanent. Gently stretching the hat while it is damp can win back a little room, but it will not return to its original size.

Need a fresh one? See all our sauna hats. Curious why boiled wool behaves so differently from pressed felt or cotton? Read Wool vs felt sauna hats.