FELT. care guide: how to clean and maintain your Merino wool sauna hat

A high-quality Merino wool sauna hat rewards a little care. Treat it well and it'll protect your hair and ears through years of sauna sessions. Like any quality wool garment, though, it needs the right kind of attention, and that's mostly about what not to do.

Merino wool is a remarkable fibre: it can absorb up to 35% of its own weight in moisture before it even feels damp, and its surface naturally resists the bacteria that cause odour (Woolmark, retrieved June 2026). That's why your FELT. hat needs far less cleaning than cotton or synthetic headwear. This guide walks through airing, spot cleaning, reshaping, and storage, the four things that'll keep your hat looking and performing like new.

Key Takeaways

• Merino wool can absorb up to 35% of its own weight in moisture before feeling damp, which is part of why it resists odour and needs less washing than cotton or synthetic fabrics (Woolmark, retrieved June 2026).
• Never machine or hand wash your felt sauna hat. Cold-water washing alone cuts wool shrinkage risk by over 85% compared with hot water, but felted wool can still distort permanently from agitation (Selvane, retrieved June 2026).
• Air your hat after every session, spot clean only when needed, and let it dry upright for 24-48 hours.
• Cedar and lavender moth deterrents lose their potency within 12-24 months as the oils evaporate, so refresh them periodically (Pointe Pest Control, retrieved June 2026).

why shouldn't you wash your sauna hat?

Felted Merino wool is naturally antibacterial, so washing isn't just unnecessary, it can permanently damage your hat. A joint study by Australian Wool Innovation, AgResearch, and Norway's SIFO institute found wool garments need washing far less often than polyester to stay odour-free (Woolmark, retrieved June 2026).

This might sound counterintuitive, especially if you're used to throwing every gym shirt in the wash. But wool fibres are exceptionally good at managing moisture and resisting the bacteria that cause odours. Unlike synthetic materials, your hat doesn't need a wash after every session, just a bit of air.

Full washing, even by hand, can cause the delicate felted wool to shrink, warp, and permanently lose its shape. The fix is simple: rely on just two methods, airing and spot cleaning, and you'll rarely think about cleaning your hat at all. Curious why we chose 4mm Merino felt in the first place? We cover the material science in more detail here.

routine care: airing after each use

Airing is the only routine care your FELT. hat needs, and it works because wool actively releases the moisture it absorbed during your sauna session. Hang the hat in a well-ventilated spot away from direct sunlight after each use, and the wool fibres will refresh themselves within a few hours.

For most people, this is genuinely all the maintenance the hat needs, week to week. No detergent, no machine, no scrubbing brush, just a hook and some airflow.

how do you spot clean a sauna hat?

Spot cleaning targets just the stained area, using a pH-neutral, enzyme-free wool detergent and cool water, never the full hat. Wool fibres have microscopic scales that interlock when agitated with heat and moisture, the same mechanism that causes shrinkage, so gentle, localised cleaning is what keeps your hat's shape intact (Selvane, retrieved June 2026).

If your hat develops a small stain or mark, here's how to deal with it without saturating the whole thing.

step 1: prepare the cleaning solution

Mix a very small amount of mild, wool-safe detergent (pH-neutral and enzyme-free) with cool water.

step 2: dab gently

Dip a clean, soft cloth into the solution and gently dab the stained area. Do not rub or scrub, as this can damage the wool fibres and spread the stain. Aggressive friction is the enemy of wool and can cause it to lose its shape or develop thin spots where the fibres have been damaged.

step 3: rinse lightly

Dampen a different clean cloth with plain cool water and gently dab the area again to remove any detergent residue.

step 4: air dry

Press the area gently with a dry towel to absorb excess moisture, then lay the hat upright on a towel or mesh rack to air dry completely, away from direct heat or sunlight.

important: a note on washing

Washing a felted wool hat, by hand or machine, combines the heat, moisture, and agitation that cause wool to shrink and distort permanently. Cold water alone can cut shrinkage risk by over 85% compared with a hot wash for woven wool garments, but felted items can still warp because the felting process is largely irreversible once it starts (Selvane, retrieved June 2026).

We strongly recommend against any form of full washing, including hand washing or machine washing. FELT. isn't responsible for any damage, shrinkage, or loss of shape resulting from washing. Stick to airing and spot cleaning, and that's never going to be a problem.

how do you reshape a sauna hat that's lost its shape?

the steam method

Steam is the safest way to reshape felted wool because it temporarily relaxes the keratin structure of the fibres without saturating them the way washing does. Hold a clothes steamer or boiling kettle 15-20cm from the felt, work in small sections until the wool turns soft and pliable, then mould it back into shape by hand. Wear heat-resistant gloves if you need to.

The same fibre property that makes spot cleaning so effective, wool's scaled surface structure, is also what makes steam reshaping work. Heat and moisture briefly open those scales just enough for the fibres to shift into a new position, then they lock back into place as the hat cools and dries. It's essentially a controlled, single-direction version of the same mechanism that causes shrinkage when it happens uncontrolled in a washing machine.

Once a section is pliable, smooth out creases or reshape the crown and brim by hand. For a perfectly rounded crown, place the damp, warm hat over a bowl or hat form while it cools and dries completely, and try not to handle it too much in the meantime, since the fibres lock into their new shape as they dry.

This works well for a crushed brim or a misshapen crown. Be gentle. You're guiding the wool into shape, not forcing it.

what is the best way to store a sauna hat?

Store your hat somewhere cool, dry, and out of direct sunlight, ideally in a breathable cotton bag (such as the one provided with your FELT. hat purchase) with a natural moth deterrent. Cedar and lavender both work by releasing volatile oils that adult moths avoid, but those oils dissipate within 12-24 months, so they need refreshing or replacing periodically to stay effective (Pointe Pest Control, retrieved June 2026).

Sunlight fades wool's natural colour over time and can degrade the fibres themselves, so a drawer, shelf, or hat stand out of direct light is ideal. Just make sure the hat is completely dry before you put it away. Avoid plastic bags or sealed containers, since trapped moisture leads to mildew and the musty smell wool is otherwise so good at avoiding.

If you have the space, a hat stand or mannequin head helps the hat hold its shape between uses. But honestly, a drawer or shelf works just fine for most people, and that's exactly where most of ours end up too.

New to sauna altogether? Our beginner's guide covers how to structure your first few sessions, so you get the most out of your hat from day one. For the full picture, our complete guide to setting up a home sauna routine covers building a sustainable home practice.

frequently asked questions about sauna hat care

how do i clean my Merino wool sauna hat?

For routine care, simply hang it to air dry after each use. If it becomes stained, spot clean the affected area only with a damp cloth and wool-safe detergent. Do not wash the hat.

can I put my sauna hat in the washing machine?

No. You should never machine wash or hand wash a felt sauna hat. The agitation and water saturation will cause it to shrink and lose its shape permanently.

what do I do if my hat gets wet?

If your hat gets damp from sweat, simply hang it to air dry. If it gets very wet for any reason, gently press out the excess water with a towel and lay it flat to air dry away from heat.

how long does it take for a sauna hat to dry?

A Merino wool sauna hat typically takes 24-48 hours to dry completely when laid flat in a well-ventilated area. Never use heat to speed up the drying process, as this can cause shrinkage and damage.

how do I fix a hat that has lost its shape?

Use steam from a clothes steamer or kettle to gently soften the felt, then reshape it by hand. The wool will hold its new form as it cools and dries.

will my sauna hat shrink if I wash it incorrectly?

Yes, washing incorrectly, machine washing, or using a dryer will cause significant shrinkage. Always use cool water to spot clean and air dry to prevent shrinkage.

how should I store my sauna hat between uses?

Store your hat in a cool, well-ventilated, dry place away from direct sunlight. Use a breathable cotton bag with cedar blocks or lavender to prevent moths. Avoid plastic storage, which can trap moisture.

is it true that wool needs less washing than other fabrics?

Yes. A study by Australian Wool Innovation, AgResearch, and Norway's SIFO institute found wool garments can go significantly longer between washes than polyester while staying odour-free, thanks to wool's ability to absorb up to 35% of its weight in moisture and bind odour within the fibre (Woolmark, 2026).