Designer knitwear and jumpers, with the pilling question answered

Merino, lambswool, Shetland and cashmere

Four fibres, four different things, and the label rarely explains the difference.

Merino is fine wool, generally under 22 microns. For scale, human hair runs between 50 and 100 microns. That fineness is why merino does not itch the way coarser wool does, and why it regulates temperature rather than simply insulating. It is the fibre to reach for if you run warm or if the jumper is going under a jacket.

Lambswool is wool 50mm or shorter from the first shearing of a sheep, taken at around seven months. It is soft, elastic and slippery. The reason it feels softer than the same sheep's later fleece is that the fibre tips have never been cut. It is not defined by fineness, which is why the question of whether lambswool is warmer than merino has no clean answer.

Shetland averages around 23 microns, ranging from 10 to 20 at the neck and shoulder up to 25 to 35 for britch wool, with an average staple length of about 3.5 inches. It is measurably coarser than merino, which is exactly why it is denser, more wind-resistant and more rustic to the touch. The breed gives 11 whole colours and 30 recognised patterns, which is why undyed Shetland yarn comes in natural shades.

Cashmere, by the industry benchmark, must be the fine dehaired undercoat of a cashmere goat, with average fibre diameter not exceeding 19 microns and no more than 3% by weight of fibres above 30 microns. That 19 micron figure is the single most useful number in any cashmere conversation. Note that this is a US labelling rule rather than UK law, so treat it as the industry standard rather than a legal guarantee.

Ranked by fineness: cashmere, then merino, then fine alpaca, then Shetland. Lambswool cannot be placed on that scale because it is defined by staple length rather than micron.

Gauge, and why two merino jumpers cost different amounts

Gauge is the number of needles per inch on the knitting machine, written as GG.

Three to five gauge gives chunky winter sweaters. Seven gauge is the workhorse for most sweater programmes. Twelve gauge and finer gives lightweight, smooth fabrics: fine-gauge sweaters, knitted polos and base layers.

Gauge changes yarn consumption, knitting time, drape, warmth and price. It is most of the reason knitwear prices vary so much, and it is a more useful thing to look at than the brand name.

Will it bobble, and is that your fault

Here is the answer no knitwear retailer gives, because it reads as a disclaimer.

Pilling, or bobbling, is caused by rubbing during wear. It forms where friction is highest: elbows, underarms, sleeves, and anywhere a bag strap sits. Woolmark's own position is that because pilling is so complex, nobody can guarantee it will not occur, and that it depends on many factors including the action of the wearer.

So it is not a fault, and it is not a sign the jumper was badly made. It is a property of spun fibre rubbing against things.

What reduces it on the design side is longer fibres, higher twist and higher cover factor. That is the real bridge between a £300 jumper and a £40 one, and it is why the expensive one should still look right in three winters.

What reduces it on your side: turn the garment inside out before washing, avoid fabric softener, and reduce abrasion where you can. For removing pills that have already formed, a battery de-pilling device is low cost and very effective, and will bring a jumper back to looking new.

How to wash it

Wool garments should be washed on the wool setting, usually gentle action at 40 degrees. If you are hand washing, use clean lukewarm water at around 30 degrees with a ten minute soak. Use a neutral, mild detergent, preferably a Woolmark recommended one. If your machine has no wool cycle, use the cold wash or the delicates cycle.

Dry flat. Knitwear specifically should be flat dried in the shade, not hung, because a wet jumper on a hanger stretches under its own weight.

Wool needs washing less often than cotton because it is naturally stain resistant, odour resistant and crease resistant. Airing a jumper overnight solves most of what you would otherwise wash it for.

What we could not establish

Sizing conventions for RRD, Altea and Thomas Maine are not published anywhere we could verify, and those three are the ones most likely to use Italian numbers rather than letters.