Merino wool: properties, care and why does it not itch?

One sweater has sat in your wardrobe since last winter and still carries not a single pill. Beside it lies another, pressed into a stiff board after two washes. The difference rarely comes from the price. Far more often it comes from the kind of wool hidden behind the label.

How does merino differ from ordinary wool?

Merino is wool from merino sheep, with a fibre far finer than in traditional wool, and it is the thickness of that fibre that decides whether a sweater itches. Standard sheep's wool has a fibre of around thirty microns in diameter, while merino usually falls between seventeen and twenty-four.

This is not a cosmetic difference. A fibre thicker than twenty-five microns is stiff enough to press against the nerve endings in your skin instead of bending, and you feel that as scratching. A finer fibre folds softly and never triggers the sensation. That is why merino can be worn straight against the body, while ordinary wool usually needs a layer underneath.

Why does merino not itch if it is still wool?

The feeling of scratching depends on the stiffness of a single fibre, not on whether the fabric is wool, so fine merino stays smooth to the touch even at a full wool composition. Below twenty-two microns almost nobody feels any discomfort.

On top of that come three qualities that matter more in daily wear than the absence of itch:

• Temperature regulation. The fibre absorbs water vapour before it turns into a drop, so it keeps you warm at ten degrees and does not overheat you at twenty.
• Resistance to odour. The structure of the fibre slows the growth of bacteria, which is why a merino sweater can be worn for several days without washing.
• Elasticity. The fibre springs back after creasing, so wool sweaters stretch at the elbows far less than cotton ones. The same quality lets a merino cardigan keep a straight line along its buttons.

That last quality is often underrated, yet it decides how a sweater looks in its second season. Cotton in the same cut stretches at the cuffs and never quite returns.

How do you read the label so you do not overpay?

The word merino on its own guarantees nothing, because what counts is the percentage of wool in the composition and the knit weight given in grams per square metre. A blend with a large share of acrylic costs less, but loses most of the qualities described above. If the vocabulary of fibres feels unfamiliar, a short guide to types of fabrics makes the label easier to read.

It is easier to base the choice on three numbers from the label than on a marketing description.

The two middle rows are enough for everyday shopping. A weight of two to three hundred grams covers autumn and most winter interiors, and at that weight you can feel the difference in fibre thickness with your hand before you even reach the fitting room.

Merino in this weight range behaves calmly: in daylight the knit looks matt and even, and in movement it falls close to the body instead of standing away in stiff folds.

How do you wash merino wool so it does not felt?

Felting is caused by three factors acting together: high temperature, friction and a sudden change in water temperature, so removing just one of them is enough. The simplest one to control is temperature.

• Water up to thirty degrees. Use the wool programme or wash by hand, always at the same temperature for washing and rinsing.
• No spinning above six hundred revolutions. Friction in the drum does more harm than the detergent itself.
• Dry flat. A wet sweater hung up stretches under its own weight by several centimetres and never returns to its cut.

The symbols on the care tag tell you which of these limits the maker set, and a guide to laundry symbols decodes them quickly. Under a merino sweater you need no thick layer: a smooth, close-knit longsleeve is enough. Washing does not need repeating often either. Airing the sweater overnight is enough, and a full wash can wait until a real stain appears.

What should you never do with merino?

Most ruined sweaters are the result of three habits carried over from washing cotton.

• Never dry merino on a radiator. Fast drying stiffens the fibre and the sweater loses its elasticity for good.
• Avoid fabric softeners. They settle on the scales of the fibre and take away the ability of wool to manage moisture, which is exactly what you pay extra for.
• Never rub a stain. Rubbing a wet patch is the shortest route to a matted, felted spot that no iron can smooth out.

It is also worth giving up storing sweaters on hangers. The shoulders push out into telltale peaks, while knitwear folded on a shelf keeps its shape much longer. The same applies to a knitted dress, which stretches at the shoulders when left on a hanger.

Is merino suitable for sensitive skin?

Usually yes, as long as the fibre is below twenty-two microns, because then it triggers no tactile reaction. With an allergy to lanolin merino can still irritate, so test the first contact on your forearm.

How often should you wash a merino sweater?

Every five to eight wears, far less often than cotton, because the fibre does not hold on to odour. Between wears, airing it overnight somewhere with a draught is enough.

Is merino warmer than acrylic?

It warms differently: acrylic insulates, while merino carries moisture away, so in changing temperatures merino performs clearly better. Standing still in frost, the difference is smaller than the price suggests.

What can you do with a felted sweater?

Soak it in lukewarm water for twenty minutes and gently stretch it out flat. It will not bring back the full cut, but it often recovers a few centimetres, and a guide on how to fix a felted sweater walks you through the rest step by step.

Go back to those two sweaters from the beginning. The one without pills almost certainly had a higher share of merino and never saw a radiator. Everything else follows from one decision at the label and three habits at the wash.