A good sock is built around the job it's doing. The fibre blend suits the use, the knit is dense enough to hold its shape without being stiff, the cuff has enough elastic recovery to stay up after fifty washes, the heel is shaped rather than guessed at, and the toe seam is flat enough that you forget it's there. Get those five right and the sock lasts. Get any one of them wrong and you notice within a week.
What actually separates a good sock from a bad one?
Not the price, and definitely not the brand on the cuff.
A sock is a small engineering problem, and it's a bit of a marvel how it's been solved. It has to stretch over a heel that's wider than the ankle it just came through, grip a leg without cutting into it, absorb or move sweat, survive being sanded against the inside of a shoe for eight hours, and then go through a washing machine and come out the same shape it went in. Nothing else in a wardrobe gets asked to do all that, and nothing else gets bought with so little thought.
Which fibres do what?
Every sock is a compromise between fibres, because no single fibre does all the jobs.
- Cotton. What it's good at: Comfort, softness, absorbing sweat, cheap to buy. What it's bad at: Holds water once wet, no stretch of its own, poor abrasion resistance. Where you find it: Everyday socks, uniform socks, most of what's in a supermarket.
- Merino wool. What it's good at: Warmth, softness at fine diameters, managing damp without feeling wet. What it's bad at: Cost, and coarse wool prickles. Where you find it: Walking, skiing, winter socks.
- Polyamide (nylon). What it's good at: Abrasion resistance, strength, holding a shape. What it's bad at: Nothing to do with comfort on its own. Where you find it: Blended into heels and toes of almost every decent sock.
- Polypropylene. What it's good at: Doesn't absorb water at all, so it moves sweat outward. What it's bad at: No warmth when still, needs blending. Where you find it: Sports and technical socks.
- Polyester. What it's good at: Cheap bulk, dries fast. What it's bad at: Feels flat, and it's the fibre that's there to pad out a blend. Where you find it: The cheap end of almost everything.
- Elastane. What it's good at: Stretch and, more importantly, recovery. What it's bad at: Degrades with heat over time. Where you find it: The cuff of every sock that stays up, often the arch too.
- Acrylic. What it's good at: Warmth and bulk cheaply, takes bright colour. What it's bad at: Pills, and doesn't wear well. Where you find it: Thermal socks, novelty socks.
We build our everyday socks around cotton. It feels lovely because it takes sweat off your skin. It then holds onto that sweat, which is exactly what you don't want inside a boot on a cold afternoon but it is for day to day wear. Polypropylene feels like nothing at all in your hand and behaves beautifully in a shoe, because water it can't absorb has nowhere to go but out through the fabric great on a cold day or while exercising but uncomfortable for day to day use.
Wool sits in the middle and is the odd one out. It carries a lot of water and still doesn't feel wet, which is why walkers and skiiers pay for it. Whether it itches comes down to how fine the fibres are. Woolmark's own guidance is that superfine merino is kinder to sensitive skin, because fine fibres bend when they press against you instead of pushing back. It comes at a steep cost, so it is most commonly used for performance ski socks.
Is cotton the best thing to make a sock from?
For sitting at a desk, it's hard to beat and for most day to day purposes (and even light exercise) it's great.
But cotton cannot be alone. It has no stretch of its own and no abrasion resistance. A 100% cotton sock falls down, because there's nothing in the cuff to pull it back, and it goes through at the heel, because cotton fibres give up against friction faster than nylon does. What good everyday socks actually contain is cotton for the feel, polyamide where the wear happens, and a few per cent of elastane so the sock stays on your leg. The ratio moves around, but that's the shape of it.
Why do socks fall down?
A sock falls down for one of two reasons. Either there was never enough elastane in the welt, which is a decision somebody made to save a fraction of a penny a pair, or the elastane has degraded. Heat is what degrades it. Every hot wash and every tumble dry takes a little off the recovery, and the sock that fitted last winter is loose this one.
The top of a sock is called the welt. It's knitted as its own band, almost always in a rib, which is why it looks like columns of raised lines. A 1x1 rib alternates one knit stitch with one purl stitch, a 2x2 rib alternates two and two. Ribbing concertinas. It contracts across the fabric and pulls back when it's stretched, which is the whole point of putting it at the top of a sock.
Rib alone isn't enough to hold a leg, so an elastic yarn is worked into the welt as well. Elastane is what gives the cuff its recovery: not the stretch, which any knitted fabric has, but the pull back to where it started. A sock with plenty of stretch and no recovery is a sock round your ankle by eleven o'clock.
The way to tell in a shop is to stretch the cuff wide with both hands, hold it for a second, let go and watch. A good welt snaps back to its original circumference and looks untouched. A cheap one comes back slowly, or comes back wider than it went.
Where does a sock rub, and why is it always the toe?
Because the toe is where the sock gets closed, and closing it leaves a seam.
A sock comes off the knitting machine as an open tube. Something has to shut the end. The cheapest method closes it on the machine itself, which is fast and leaves a small ridge running across the toes. A linking step done afterwards lines up each loop of the toe with each loop of the body and joins them one at a time.
That ridge is the single most common complaint about socks, and it isn't only about comfort. A raised seam is the highest point inside the shoe, so it takes more friction than the fabric around it, and it tends to be where a sock goes first.
For most purposes that is fine. On sports and performance socks the seam is minimised to cut the friction.
Does a sock hold its shape after washing?
If the knit is dense and the elastane hasn't been cooked, yes, for a long time.
Three things change it. Cotton shrinks a little on a hot wash and keeps shrinking slowly. Elastane loses recovery with heat, gradually and in one direction only. And a loose knit relaxes and grows, because big loops have more room to move than small ones. All three are made worse by the same thing. A hot wash and a tumble dryer will finish a good sock years early. Wash cool, skip the dryer.
What wears out first?
The heel, the ball of the foot and the toe, in whatever order your gait decides.
Why does a cheap sock feel cheap?
You can usually feel it in about four seconds, and every one of those four seconds is a cost decision somebody made.
- Polyester in place of cotton or nylon. It's the bulking fibre. It costs less than what it's standing in for and it feels flat and slightly slick against skin.
- A loose knit at a low needle count. Fewer, bigger stitches use less yarn. The fabric feels thin and papery and you can see through it.
- Elastane only in the welt, and not much of it. Cheapest way to get a sock that stays up in a shop and not in a week.
- No shaped heel. A straight tube is faster to knit and skips a whole stage of the machine's work.
- A ridged toe seam. Closing on the machine rather than linking afterwards saves the most expensive minute in sock manufacture.
30 second guide to spotting a shoddy sock
- The blend. What to do: Read the label before anything else. What good looks like: A named comfort or performance fibre in the majority, polyamide present, elastane between roughly 1% and 5%. Heavy polyester is a warning.
- The welt. What to do: Stretch the cuff wide, hold, release. What good looks like: Snaps straight back to the same circumference.
- The heel. What to do: Look at the shape with the sock flat. What good looks like: A visible pouch sitting at an angle to the leg, not a straight tube.
- The toe. What to do: Turn it inside out and run a thumb across the end. What good looks like: A flat join you can barely feel, rather than a hard ridge.
- Reinforcement. What to do: Look inside at heel and toe. What good looks like: Denser, often differently coloured yarn exactly where the friction is.
Frequently asked questions
What is the best material for socks?
It depends entirely on what the sock is for, but the quick and general answer is cotton. Cotton is comfortable and absorbent and suits everyday wear. However for sport, a synthetic that doesn't absorb water beats cotton, because cotton holds sweat against the skin inside a shoe. Whatever the main fibre, a good sock also carries polyamide for abrasion and a few per cent of elastane for recovery.
Why do my socks keep falling down?
The cuff has lost its recovery, or never had enough. The top of a sock is a ribbed band with an elastic yarn worked into it, and elastane is what pulls it back after being stretched. Either there wasn't much elastane there to start with, or heat has degraded it. Hot washes and tumble drying are what do the damage, so wash cool and keep socks out of the dryer to prolong your lucky pairs life.