Make it last
How to Wash Merino Wool Without Felting It
30°C wool cycle, no agitation, lay flat. Superwash can take a machine. Untreated merino wants a basin and a no-rinse lanolin wash.
Updated 20 Aug 2026 · 7 min read · how to wash merino wool
30°C, no agitate, low spin
Wool fibers are covered in microscopic scales. Heat plus mechanical agitation plus moisture is the industrial recipe for felt: the scales open, slide, and lock. A 30°C wool cycle exists to avoid that recipe. A 40°C cotton cycle with a hard spin is how a $90 base-layer becomes a child's top.
Read the tub on the care label. Two bars and a 30 is a wool cycle. A hand in the tub is a basin. An X over the tub is dry-clean or spot-clean only — rare on merino jersey, more common on tailored wool. Use a mesh bag so the sweater does not rub a zipper. Liquid wool wash, not powder, not ordinary enzyme detergent if you can avoid it. Enzyme formulas are built to digest protein; wool is protein.
Superwash versus untreated
Superwash merino has had its scales stripped (chlorine Hercosett is the old industrial method) or coated with a polymer so the fiber cannot felt as easily. It can usually take a gentle machine cycle and sometimes a low dryer, which is why it dominates travel tees and next-to-skin base layers. The trade: it can feel slightly slicker, it often pills more, and it can lose some of the odor resistance people buy merino for.
Untreated merino still has its scales. It drapes better, takes a press better, and holds lanolin’s faint water resistance. It also felts if you treat it like cotton. Hand wash, or a true wool cycle you have tested on a hem first. If you are choosing between fibers for a knit you will wear for a decade, the merino versus cashmere comparison is the next read; washing is what keeps either one in the rotation.
| Superwash merino | Untreated merino | |
|---|---|---|
| Machine 30°C wool cycle | Usually yes, mesh bag, low spin | Only if the label’s tub says so |
| Hand wash | Optional | The default |
| Felt risk | Low | High if you agitate or overheat |
| Odor control | Good, sometimes reduced | Best of the two |
| Travel load | The point of Superwash | Risky in a hotel machine |
Lay flat like you mean it
Wet wool is heavy. A hanger stretches the shoulders into points and lengthens the body overnight. After washing, press water out with your palms, roll the piece in a dry towel, stand on the roll, unroll, and lay the sweater flat on a second dry towel or a mesh rack. Square the hem. Align the sleeves. Let it dry out of the sun. A full dry is often 12–24 hours; do not finish it in a tumble dryer “just for 10 minutes.”
This is the same reason merino earns a place in a travel capsule: it carries fewer days of odor per wash, but only if you can dry it flat in a hotel. A sink wash at night, towel-roll, rack over the bathtub, wear in the morning. That loop fails if you wring it and hang it on a door hook.
Lanolin soaps, and what not to use
No-rinse wool washes (Eucalan, Soak, Unicorn Fibre, a handful of others at $12–18 a bottle) are pH-balanced for protein fiber. Some add a little lanolin back. You soak 15 minutes, press, and skip a running-water rinse that would felt the surface. A teaspoon in a basin is enough for a sweater. Ordinary dish soap strips oils. Chlorine bleach dissolves wool. Fabric softener coats the fiber, kills the wicking and odour resistance you paid for, and helps the next wash felt. Do not use it.
Superwash often pills in the first month as short fibres leave; that is pilling, not felting. Comb them off. Do not take a fabric shaver to a 17-micron jersey.
Questions, answered
- Can I put merino wool in the washing machine?
- Superwash, yes, on a 30°C wool or delicate cycle in a mesh bag, low spin. Untreated merino, only if the label’s washtub agrees. Never a normal cotton cycle.
- Why did my merino sweater shrink?
- Felting, not mysterious shrinkage. Heat plus agitation locked the scales. It is usually irreversible. Next time: cooler, less motion, lay flat.
- Do I have to use a special wool detergent?
- For untreated merino, yes — a no-rinse wool wash is the least work and the least felting. A very mild liquid on Superwash jersey is tolerable. Skip enzymes and powder.
