How to wash merino wool
Merino wool is more washable than its reputation suggests. The fine fibers felt less easily than coarser wools, and many brands now produce merino that handles a machine wash cycle reliably. The key rules are cold water, a gentle cycle, wool-safe detergent, and never hanging it wet to dry.
Why merino wool is more washable than regular wool
Merino wool comes from merino sheep and has superfine fibers — typically under 20 microns in diameter, compared to 30 or more for coarser wools. These finer fibers have a smaller, less pronounced surface scale structure, which makes them far less prone to felting when agitated. Many merino garments are also treated with a light surface treatment that further reduces shrink risk. The result is a wool that many brands confidently label as machine washable, which is not true of regular wool.
Machine washing merino
Use the wool or delicate cycle on your washing machine with cold water. Select a slow or no-spin speed — high spin agitates fibers and raises the risk of felting. Use a detergent formulated for wool: look for labels that say wool-safe, delicate, or enzyme-free. Standard detergents contain enzymes that break down protein fibers, and wool is a protein fiber. A mesh laundry bag adds an extra layer of protection against friction.
Hand washing merino
Fill a basin with cold water and a small amount of wool-safe detergent. Submerge the garment and gently press and squeeze the water through the fabric — do not scrub, twist, or wring. Let it soak for 5 to 10 minutes. Rinse thoroughly in water of the same temperature, as sudden temperature changes can also cause felting. Gently press out excess water. Never wring.
Drying merino
Always lay merino flat to dry. Do not hang a wet merino garment — water adds significant weight and will stretch the fabric, permanently distorting the shape, particularly at the shoulders and hem. Lay it on a clean dry towel, reshape it to its original dimensions while damp, and allow it to air dry away from direct heat or sunlight. Most merino garments should not go in the tumble dryer unless the care label specifically permits it.
How often to wash merino
Merino wool has natural odor-resistance properties. The fiber structure and lanolin content inhibit bacterial growth, which means a merino base layer or T-shirt can be worn multiple times before it needs washing. Many merino wearers wash after 3 to 5 wears, or when the garment is visibly soiled. Airing merino outside between wears extends the time between washes further and helps it release any moisture it has absorbed.
What causes merino to shrink
Merino shrinks when three conditions combine: hot water, agitation, and heat drying. Heat causes wool fibers to swell. Agitation causes the surface scales to interlock and lock the fibers together permanently — a process called felting. Heat drying sets this change. Avoid any one of these three and the risk drops substantially. Cold water, gentle cycle, and flat drying will preserve merino in near-original condition through many washes.
Frequently asked questions
Can merino wool go in the washing machine?
Many merino garments can, yes. Use the wool or delicate cycle on cold, with a slow spin and a wool-safe detergent. Always check the care label first — some structured or heavily knit merino pieces recommend hand washing or dry cleaning.
Does merino wool shrink?
Merino will shrink if washed in hot water, agitated heavily, or tumble dried on heat. Cold water, a gentle cycle, and flat drying prevent shrinkage reliably. Merino is significantly more resistant to shrinking than coarser wools but is not immune.
How often should you wash merino wool?
Less often than most fabrics. Merino has natural odor-resistance, so a base layer or T-shirt can typically be worn 3 to 5 times before washing, and a sweater worn even less frequently. Air it between wears and wash only when needed.
Can you tumble dry merino wool?
Generally no. Lay merino flat to dry unless the care label specifically says tumble dry is safe. The combination of heat and tumbling agitation is the most reliable way to shrink and felt merino. Some brands treat their merino for machine drying, but this is not the default.
What detergent is best for merino wool?
Use a detergent labeled wool-safe, delicate wash, or enzyme-free. Standard laundry detergents contain protease enzymes that attack and break down protein fibers like wool. Brands like Eucalan, Woolite Delicates, and Sonett Wool & Silk are commonly recommended.
Every brand in The Plain Thread directory uses natural fibers. Browse merino wool clothing brands.
Browse merino brands