Mulberry Silk: What It Is and How to Recognise Quality
Mulberry silk is silk spun by the domesticated silkworm Bombyx mori, raised on the leaves of the mulberry tree. That controlled rearing produces exceptionally long, even threads, which is why mulberry silk is widely regarded as the finest of the silk varieties. It's also the most widely used term in silk marketing, usually next to numbers like “22 momme” or “Grade 6A” that rarely get explained. This guide covers what sets mulberry silk apart from other silk, what those numbers mean, and how to check quality before you buy.
What is mulberry silk?
Almost all silk used for textiles begins as the cocoon of a silk moth caterpillar. Mulberry silk comes from Bombyx mori, a species domesticated over thousands of years and fed on mulberry leaves. A single cocoon can unwind into a continuous thread of over a kilometre, and those long, uniform threads produce a particularly smooth, fine, and even fabric.
The counterpart is wild silk, often sold as tussah silk. It comes from various wild moth species and has a coarser, more textured character. For pillowcases and bedding, mulberry silk is the usual choice: the smooth surface is the whole point of sleeping on silk.
Momme: the number that matters most
Momme (abbreviated mm) is the traditional unit for the weight of silk fabric. One momme equals roughly 4.3 grams of silk per square metre, so a 22 momme pillowcase carries about 95 grams of silk per square metre. A higher number means a heavier and, as a rule, more densely woven fabric.
| Momme | What it tells you |
|---|---|
| under 19 | thinly woven, entry-level |
| 19 to 21 | good quality, the usual lower bound for everyday use |
| 22 to 25 | premium range: densely woven with a full, smooth feel |
| over 25 | very heavy and dense, mostly luxury bed linen |
For silk pillowcases, 22 momme has established itself in the trade as the go-to premium specification: dense enough to feel substantial without making the fabric heavy. If a product page doesn't mention momme at all, treat that as a warning sign.
Grade 6A: how raw silk is rated
The raw silk itself is graded separately from the finished fabric. Grading runs from A to F, with the A range subdivided up to 6A, the highest classification. It reflects measurable criteria such as the fineness, evenness, purity, and strength of the thread. Momme and grade describe two different things: the grade rates the raw silk, momme the weight of the woven fabric. A trustworthy listing usually states both.
Silk vs satin: a fibre versus a weave
The most common mistake when buying silk: satin isn't a fibre, it's a weave. A “satin pillowcase” can be woven from polyester, viscose, or silk, and in most shops it's polyester. Words like “silky” aren't fibre names either. What counts is the fibre composition on the label: “100% silk” or “100% mulberry silk” means the natural material. Polyester satin feels similarly smooth in the shop, but it behaves differently through the night. It absorbs barely any moisture and tends to build up static.
How to spot real mulberry silk
- Read the fibre content. The legally binding information is the fibre composition on the label: it should state “100% silk”; “mulberry” is the seller's additional note on origin. “Satin” or “silky feel” with no fibre statement at all points to polyester.
- Look for the momme count. Reputable sellers state it. By trade convention, good quality starts at 19 momme; 22 momme is the usual premium standard.
- Check the raw-silk grade. “Grade 6A” marks the highest classification of the raw silk.
- Verify the certificates. OEKO-TEX labels such as STANDARD 100 or MADE IN GREEN stand for testing against harmful substances, MADE IN GREEN additionally for traceable, certified production. GOTS certifies textiles made from organically grown fibres, with environmental and social criteria audited through processing. Both can be checked online, MADE IN GREEN via its label ID and GOTS via the supplier's licence number.
- Put the price in context. A very low price proves nothing on its own, but it's a reason to read the fibre statement twice. Suspiciously cheap “silk” often turns out to be polyester satin.
You'll also come across the burn test: a snipped thread of real silk smells like burnt hair and leaves a brittle ash, while polyester melts. It can separate silk from polyester, but it damages the fabric and only answers the question after you've paid. Before you buy, the fibre statement and the certificates are the evidence you can actually check.
What mulberry silk does for hair and skin, and what it doesn't
Two properties explain why mulberry silk has such a following in hair and skin care. The first is the smooth surface: hair glides across silk instead of catching on a rougher weave. Less friction through the night means less mechanical stress on the hair, and many people report less tangling and frizz in the morning. Skin gets the same mechanical break: the fabric slides under the face instead of dragging against it, and side sleepers in particular often report waking with fewer crease marks.
The second property: a densely woven silk cover takes up less of your evening skincare than absorbent cotton does, so more of it stays on your skin overnight. Silk also feels cool to the touch in summer and sleeps comfortably warm in winter.
Equally clear is what silk doesn't do: there's no solid clinical evidence that it helps against acne or bacteria. What you can realistically expect is less friction on hair and skin and a pleasantly cool feel.
Mulberry silk at RENESSY
The pillowcases in our silk pillowcase collection put the checklist above into practice: 100% organic mulberry silk at 22 momme and Grade 6A, woven with silk on both sides rather than a cotton or polyester back. GOTS and OEKO-TEX MADE IN GREEN provide the verifiable paper trail, Dermatest has tested and certified the skin compatibility, including for sensitive skin, and a hidden YKK zip sits under an inner fabric flap.
Frequently asked questions
What does 22 momme mean?
22 momme means the fabric weighs about 95 grams of silk per square metre. In the trade it's the established premium specification for silk pillowcases: densely woven and substantial to the touch.
Why is it called mulberry silk?
Because the silkworms that produce it are fed on mulberry leaves. The name distinguishes silk from the domesticated Bombyx mori moth from wild silks such as tussah, which are coarser and less even.
Is mulberry silk vegan?
No. Silk is an animal product, and in conventional production the silkworms are killed inside the cocoon. Certifications such as GOTS cover environmental and social standards along the textile chain, but they don't change that.
How do you care for mulberry silk?
Gently, and always by the care label: cool water at a maximum of 30 °C (86 °F), a protease-free detergent, no tumble dryer, air-drying instead. Our guide on how to wash silk walks through every step.