Cashmere does not shrink the way cotton shrinks. It felts, which is a different and more permanent problem. Wool and cashmere fibres are covered in microscopic scales, and heat plus friction plus alkaline detergent makes those scales interlock and lock together, which is why a hot machine cycle can return a jumper two sizes smaller and slightly stiff. Cool water and no agitation, and almost nothing happens.

So the practical answer is that hand washing in lukewarm water no warmer than about 30C with a mild wool detergent is the safe route, and most cashmere houses say so themselves. Do not wring it, do not hang it wet, and never tumble dry it. Roll it in a towel to take the water out and dry it flat. Care guidance from cashmere specialists including Cashmere Company and Rifò is consistent on all of this, and it is the reverse of how most people treat a jumper they paid several hundred pounds for.

Below, the turtleneck, the cardigan and the everyday crew, plus what each fibre blend actually does after ten washes. &Daughter, Jenni Kayne, DÔEN and Joseph feature, and White & Warren gets the Label Love.

The turtleneck is the shape where fibre quality shows fastest, because it sits against your neck all day and you will simply stop wearing anything scratchy. This is the piece to spend on, and the piece where I would rather have merino that feels good than cashmere that does not.

What to check. Look for a stated micron count or at least a two-ply construction, since single-ply cashmere is thinner, warmer per gram and much quicker to pill. Fine cashmere is generally under 19 microns. Pull the neck gently and let go: a good rib springs back, a cheap one stays stretched, and that is the part that will look tired first. Jenni Kayne, St. Agni and Tibi cover the considered end, Kule and Splendid the version you can throw in a bag, and Joseph's mock necks are the best value ratio in this grid.

A cardigan is the most useful knit you can own because it is the only one you can take off gracefully, and it is also the one most likely to lose its shape, since buttons and pockets put load on the knit in specific places.

Buying notes that have saved me money. Check the button band: it should be firmly knitted or faced, because a floppy band pulls into waves after a month. Look at whether the shoulder seam sits on your shoulder, since a dropped shoulder on a heavy knit will keep dropping. And store cardigans folded rather than hung, because a hanger stretches the shoulders permanently. ATM Collection and DÔEN do the fine cashmere versions well, Frank & Eileen and Nili Lotan the substantial ones, and Jenni Kayne and Rails the cropped shapes that work over a dress.

The crew is the workhorse, so buy it for wear rather than for feel in the shop. The softest jumper on the rail is very often the one that pills within three wears, because loose, long-haired surface fibres feel wonderful and then migrate.

Here is the thing nobody tells you: pilling is not a defect, it is surface fibres working loose, and a new cashmere jumper will pill most in its first few wears and then settle. A cashmere comb, used dry, is genuinely the whole solution. What is not fixable is felting, so keep it away from heat. A.L.C. and Nili Lotan sit at the top of this grid, ATM Collection and CAMI NYC in the sensible middle, Faherty and Ganni at the price where you will not agonise over it. If it is your first real cashmere purchase, buy a crew in a mid grey or oat and wear it twice a week.

White & Warren is a single-category brand and that is exactly why it is here. The whole business is cashmere and cashmere blends, and the range is organised by weight rather than by trend, which is far more useful when you are trying to work out what you will actually wear.

The travel wrap is the piece they are known for and the one I would defend at the price, because it does the work of a scarf, a cardigan and a blanket on a plane. The featherweight styles are the ones for layering under a coat, the cashmere linen blends are the answer to a cold office in July, and the cable knits are the substantial end. Sizing runs generous through the body on purpose. If you want the softest thing in the range, look at the superfine wrap. If you want the thing that lasts, look at the cable.

The forever-evolving edit, this month all knitwear.

&Daughter argyle cashmere foulard, Scottish spun and the nicest thing here.

Jenni Kayne cashmere Jet turtleneck, the plain one that ends the search.

St. Agni wool cardigan in dark charcoal melange, for people who find cream impractical.

Rat & Boa Vida jumper, a mohair cowl neck and the one indulgence on the list.

ATM Collection cashmere wide rib cardigan in black, the shape I wear most.

Frank & Eileen Gaia in merino, proof that merino does not have to feel like sportswear.

CAMI NYC Leith wool cashmere in oat, the colour that goes with everything I own.

Staud Gino cashmere sweater, a slightly louder cut for the same money.

The knitwear rules I actually follow.

Wash less than you think. Cashmere is naturally odour resistant, and airing a jumper overnight is usually enough. Every wash is a small risk, so take fewer of them.

Cool water, flat drying, no exceptions. This is the whole of knitwear care and it takes ten minutes.

Buy a comb, not a razor. A comb lifts pills off. A razor cuts the surface and thins the knit.

Fold, never hang. A season on a hanger will stretch the shoulders of a good jumper beyond saving.

If you take one thing away: judge a knit by how the rib springs back, not by how soft it feels in your hand. Softness on the rail is often loose fibre that will pill, and a firm rib is the thing that will still look right in three winters.