Silk vs Satin: What's Actually the Difference?
Most people cannot tell the difference between silk and satin by looking at them. And that is exactly the problem — because one is a natural fibre made by silkworms, and the other is often 100% polyester.
Both are sold as "luxurious." Both have that characteristic sheen. But one regulates your body temperature while you sleep. The other traps heat and moisture against your skin all night. One biodegrades at the end of its life. The other sits in landfill for around 200 years.
Here's what they actually are — and how to tell them apart.
The short answer
This confuses almost everyone, so let's start here.
Silk is a fibre. It's a raw material — like cotton or wool. It comes from silkworms, specifically the cocoons they spin around themselves. Those threads are unwound, spun together, and woven into fabric.
Satin is a weave. It's not a material at all — it's a way of interlacing threads. You can make a satin weave from silk threads, polyester threads, nylon, or anything else. The satin weave is what gives that characteristic sheen on one side and matte finish on the other.
So when something is labelled "satin," that tells you almost nothing about what the fabric is actually made of. When something is labelled "silk satin" — like most quality silk slips — it means silk fabric woven in a satin pattern. When something is just labelled "satin" with no fibre content listed? It's almost certainly polyester.
What silk actually is
Silk is produced by the Bombyx mori silkworm — fed exclusively on mulberry leaves, which is where the term "mulberry silk" comes from. The worm spins its cocoon from a single protein fibre. One cocoon produces a continuous thread that can be up to a kilometre long.
The reason silk feels the way it does comes down to its protein structure. Silk fibroin is structurally similar to human skin — it's biocompatible, which is why it feels so natural against your body. It doesn't irritate sensitive skin. It doesn't strip moisture from your face or hair the way cotton does. Its natural smoothness reduces friction, which is why sleeping on silk is genuinely better for your hair and skin — not just a marketing claim.
Silk also naturally regulates temperature. The fibre structure breathes — it allows air to circulate — but it also has a mild insulating quality that means you don't overheat in summer or get cold in winter. It adjusts to your body rather than fighting it.
What is momme?
Mulberry silk is graded by density, measured in momme (written as "mm"). A higher momme weight means more silk per square metre — a heavier, more durable fabric. Most silk sleepwear sits between 19 and 22 momme. Anything below 12 momme is quite delicate and prone to snagging. Anything above 25 starts to feel like a formal fabric rather than something you'd sleep in.
The & moon silk slips are made at 19 momme — right in the sweet spot for sleepwear. Heavy enough to drape properly and last for years. Light enough to sleep in every night.
What satin actually is (the polyester kind)
Polyester satin is made from petroleum-derived synthetic fibres woven in a satin pattern. That weave gives it the same shiny surface as silk satin, which is why they look so similar in photos and even in person at first glance. But the similarities end there.
Polyester doesn't breathe. It traps heat and moisture against your skin. If you've ever woken up in the middle of the night feeling clammy and overheated in what you thought was a luxurious slip — this is why. Synthetic fibres can't regulate temperature because they have no natural moisture-wicking properties.
Polyester has a static charge. It clings in a way that silk doesn't. Silk drapes and falls away from your body. Polyester sticks.
Polyester doesn't break down. A polyester satin slip takes around 200 years to decompose. In that time it sheds microplastics every time it's washed, which end up in waterways and eventually in the food chain.
None of this means polyester satin is useless — it's cheap, durable in its own way, and easy to care for. But it's not silk, and it shouldn't be priced or positioned as if it is.
How to spot the difference at home
If you're looking at something that claims to be silk — whether you're shopping online or holding a piece in a store — here are four ways to tell what you're actually dealing with.
1. The price test
Real silk is expensive to produce. If something is $20 and labelled "silk," it is not silk. Genuine silk sleepwear starts at around $60–70 AUD for a simple slip. That's not because brands are being greedy — it's because the raw material costs what it costs. If the price seems too good to be true for silk, read the label.
2. The label test
A genuine silk garment must by law list its fibre content. Look for "100% silk" or "100% mulberry silk." Terms like "satin," "silky satin," "silk-feel," or "charmeuse" without a fibre content listed are red flags. Charmeuse is a weave type — like satin. Charmeuse without a fibre content could be silk charmeuse or polyester charmeuse. The fibre content is what tells you.
3. The touch and warmth test
Silk warms to your body temperature almost immediately. Hold it against your skin and within a few seconds it feels like part of you — not like a separate cool or clammy material. Polyester stays cooler for longer and often has a slight artificial slipperiness. Silk has a very subtle natural texture — not rough, but not perfectly frictionless either.
4. The burn test
This is the definitive test. Pull a single thread from an inside seam (so you don't damage the garment) and hold it to a flame.
Silk is a protein fibre. It burns slowly, self-extinguishes when you remove the flame, and leaves a fine, crushable ash. It smells like singed hair — because biologically, that's very close to what it is.
Polyester is a plastic. It melts rather than burns. It smells chemical and acrid. It leaves a hard little plastic bead that you cannot crush between your fingers.
That's it. Thirty seconds and you know exactly what you're dealing with.
Why it matters for sleepwear specifically
You spend a third of your life asleep. The fabric in contact with your skin for those 7 or 8 hours is affecting your skin, your hair, your body temperature, and your sleep quality. Most of us spend real money on skincare routines and pillowcases — and then sleep in a $20 polyester set without thinking twice.
Silk's natural protein structure means it doesn't absorb moisture from your skin the way cotton does — it helps your skin retain its natural moisture overnight. For your hair, the smooth surface creates almost no friction, which reduces the breakage and frizz that comes from sleeping on rougher fabrics. These aren't marketing claims — there's genuine dermatological research behind both.
And then there's the temperature. If you run hot at night, silk breathes in a way polyester simply cannot. If you get cold, it has a natural insulating quality. It adjusts to you rather than working against you.
There's also just the feeling of it. Getting into bed in something that feels genuinely beautiful is a small thing that turns out not to be small at all. It's the difference between your bedtime routine feeling like something you have to do, and something you actually look forward to.
What to look for when you buy
- Fibre content on the label: "100% silk" or "100% mulberry silk"
- Momme weight: 19–22 momme for sleepwear is the ideal range
- Price: Real silk at an accessible price exists, but it won't be $20
- If in doubt: the burn test never lies
The sleepwear market is full of "silk-feel" products at silk prices. That's worth knowing before you buy.
Written by Riccy P, founder of & moon
& moon makes 100% Vietnamese mulberry silk slips designed in Australia. 19 momme crepe satin weave. Four colours. Shop the slips →