What is mulberry silk? Meaning, grades, momme, and how to tell if it's real

In short: mulberry silk is silk from one species, the domesticated silkworm Bombyx mori, which is raised by people and fed on mulberry leaves. Its thread is continuous, fine (10 to 24 micrometers) and even, while wild silks such as tussah are thicker and irregular. The grade (6A, 5A…) rates that thread; the momme (19, 22, 25…) is the weight of the fabric. To check it: the label, the weight, and a burn test on a single thread.

"Mulberry silk" is printed on nearly every silk pillowcase and sleep mask. It sounds like a luxury tier. It is really the name of a species. Here is what the term guarantees, what it doesn't, and how to check it yourself.

What is mulberry silk?

Mulberry silk is silk spun by Bombyx mori, the domesticated silkworm, also called the mulberry silkworm because it feeds on mulberry leaves. That is the whole meaning of the name: the silk of the worm that eats mulberry.

This silkworm no longer exists in the wild. Domesticated in China at least 5,000 years ago, it depends entirely on humans to survive (Wikipedia, "Bombyx mori"). Each cocoon is one continuous thread, from 300 to about 900 meters long according to the same source. That continuity is what defines mulberry silk: a long, fine, even filament, reeled off in one piece.

The word itself has a story. Silk comes from Late Latin sericus, from the Greek Seres, the name given to the people of China (Wiktionary). In French, mulberry silk is soie de mûrier.

What is mulberry silk made of?

Two proteins. Raw silk is mostly fibroin, about 75 to 80% of its weight, coated in a gum called sericin, about 20 to 25% (Wikipedia, "Silk"). Degumming dissolves the sericin, and that is what gives the fabric its luster and slip. So soft silk is almost pure fibroin, a protein whose amino acids form beta-pleated sheets.

No cellulose, no plastic. The mulberry feeds the worm; it does not end up in the thread. Mulberry silk is an animal fiber.

Does the silkworm really eat mulberry?

Almost exclusively, yes: it prefers white mulberry, will eat other mulberry species, and sometimes the leaves of other plants. It can also be raised on an artificial diet (Wikipedia, "Bombyx mori"). A 2026 study notes that artificial feed is spreading on silk farms, and that a reliable way to tell the cocoons of the two diets apart was missing: its amino acid analyses found no significant difference, and the researchers had to look for chemical traces of the diet in the silk to separate them. It looked at cocoons, not finished fabric. So the name tells you the worm, not necessarily its menu.

The full story, from farm to thread: where silk comes from.

Is mulberry silk real silk? Is all silk mulberry silk?

Yes, it is real silk. It is the best known kind: Wikipedia calls it "the best-known silk", obtained from the cocoons of the mulberry silkworm reared in captivity. EU Regulation 1007/2011 defines silk as fiber "obtained exclusively from silk-secreting insects", with no distinction between species.

No, not all silk is mulberry silk. There are more than 500 species of wild silkworms, and only a few are used for cloth (Wikipedia, "Wild silk"). The eri silkworm eats castor leaves; tussah worms feed on forest trees. A label that just says "silk" doesn't tell you which worm made it.

Mulberry silk vs tussah, muga and eri

Wild silks are usually harvested after the moth has left the cocoon, which cuts the thread: no single long filament. They generally give a tougher, rougher silk than Bombyx mori, and one that is harder to bleach and dye (Wikipedia, "Wild silk").

Sources: Wikipedia, "Wild silk", for species, food, thread and color; review PMC12926875 (2026), table 2, for diameter and strength; Wikipedia, "Bombyx mori", for thread length. "n/a": none of these sources gives the figure.

The table in one line: a mulberry thread is at least twice as fine as a tussah thread. Its edge is fineness and evenness, which is to say softness. Not strength: under tension, the thicker tussah does better.

Mulberry silk vs satin and charmeuse

These words don't describe the same thing. Some name a fiber, others a way of weaving.

One thing you can check in ten seconds: the word "satin" does not appear once in EU Regulation 1007/2011, the text that sets textile fiber names. So a "mulberry silk satin pillowcase" makes perfect sense: mulberry silk, woven as satin. A "satin pillowcase" on its own says nothing about what it is made of.

Mulberry silk grades: what does 6A mean?

The grade rates the raw silk thread, the one reeled off the cocoons. Not the finished fabric, not your pillowcase, not your mask.

The FAO describes how it works: testers measure the thread's size deviation, evenness, cleanness (major defects such as slubs), neatness (small defects), tenacity, elongation and cohesion. The grade is set by the weakest result: one poor test is enough to pull the whole lot down. Grades are written with A's: 4A down to B on the International Silk Association scale, 5A down to D in the Japanese method, according to the same source. Sellers present 6A as the top of the Chinese scale, set by the national standard GB/T 1797. We have not been able to read that standard, so we can't confirm it.

• 6A: the highest grade you will see on sale. A very even thread with very few defects.
• 5A, 4A, 3A…: threads that are a little less even, or have more defects.
• "7A", "6A+": neither of the two scales the FAO describes goes above 5A.

Worth knowing before you buy: on a product page, the grade is declared by the supply chain and repeated by the seller. As far as we know, there is no public database to check it against, the way you can look up an OEKO-TEX number. It is a clue about the thread, not proof about the product.

What does momme mean in silk?

Momme (written "mm") is the weight of a silk fabric. By definition, it is the weight in pounds of a piece 45 inches wide and 100 yards long (Wikipedia, "Units of textile measurement"). In metric terms, 1 momme is about 4.34 g/m²: 22 momme is about 95 g/m², 19 momme about 82 g/m², 25 momme about 109 g/m².

Source: Wikipedia, "Units of textile measurement", Mommes section. The g/m² conversion is our own arithmetic (1 lb = 453.6 g; 45 in × 100 yd = 104.5 m²).

Momme only compares within one weave: a 35 momme noil is not a denser charmeuse, it is a different fabric. And no standard sets an "ideal" momme for any product. What the market sells can be counted: on Amazon.fr in July 2026, silk pillowcases came in 19, 20, 22 and 25 momme. Why we chose 22 for our mask: 22 momme silk, what the number means.

How to tell if it's real mulberry silk

No single test does everything. Each one answers a different question.

1. The label names the fiber. In the EU, fiber content must be stated, and shown before purchase, online included (Regulation 1007/2011, Article 16). Look for "100% silk", ideally "100% mulberry silk". "Satin", "silky" or "silk feel" are not fibers.
2. The momme figure, and a kitchen scale. Momme is a weight, so it can be checked. A 20 × 30 inch pillowcase has two sides, about 0.77 m² of fabric: at 22 momme that is roughly 74 g (2.6 oz) of silk; at 19 momme, roughly 64 g (2.3 oz). Seams, flap and zipper add weight on top. If your scale reads well below that, the stated momme doesn't hold up. This doesn't work on a sleep mask, which has padding inside.
3. The burn test tells you if it's a protein. Take a loose thread from a seam allowance, hold it with tweezers over a sink. Silk burns slowly with a small flame, goes out quickly on its own, and its ash crushes between your fingers with a smell of burnt hair or feathers; polyester leaves a hard black residue (French Wikipedia, "Soie"). Limits: blends muddy the result, and the test cannot tell mulberry from tussah. Both are silk.
4. Looks point the way, they don't settle it. Mulberry thread is fine and even; wild silk is thicker and less regular. But polyester satin is even and shiny too.
5. An OEKO-TEX number doesn't say it's silk. It shows the textile was tested for harmful substances, and you can verify it online. It says nothing about the fiber or the momme.

And price? It proves nothing either way. A small item holds very little fabric, and a high price can pay for the brand more than for the fiber.

What mulberry silk changes on a sleep mask

A sleep mask sits on your face all night, so what matters is the surface touching your skin. Mulberry silk is made of continuous filaments hundreds of meters long, where cotton is made of short fibers: it glides instead of catching. It also takes up about 11% of its weight in moisture, and its high emissivity for infrared light makes it feel cool to the touch (Wikipedia, "Silk"). That is a mechanism, not a promise of better sleep. A mask's real job is to block light.

For our 22 momme mulberry silk sleep mask, we went after both. The silk comes from a certified producer. And the shape is built around light: a soft 12 mm dome over the eyes, and an elastic strap covered in silk, with no buckle or Velcro, one size.

To see how it compares with the others: our comparison of eleven silk sleep masks.

And on a pillowcase?

A pillowcase is not a bigger sleep mask. It takes your face, your hair, your night cream, and it gets washed far more often. Silk loses up to 20% of its strength when wet, and its elasticity is moderate to poor: stretched even a little, it stays stretched (Wikipedia, "Silk"). Two takeaways: wash it gently, and check the size before you buy.

In bedding sets, momme can change from piece to piece: you will find a duvet cover sold as 25 momme bundled with 20 momme pillowcases under one listing. Ask for the figure piece by piece. To choose one: our comparison of ten silk pillowcases. What silk really does for skin and hair: the benefits of silk, what the science says.

Caring for mulberry silk

• A pH-neutral detergent with no enzymes: proteases digest fibroin the way they digest a stain.
• No bleach: it breaks down the protein and yellows the fiber.
• Don't wring or twist: wet silk is at its weakest. Roll it in a towel, dry flat.
• Dry in the shade: light, UV included, degrades fibroin.

The full method: how to wash silk without damaging it. A piece that came out stiff or dull isn't always lost: how to restore stiff or dull silk.

Mulberry silk FAQ

What does mulberry silk mean?

It means silk from the mulberry silkworm, Bombyx mori: the domesticated silkworm, fed on mulberry leaves. The name refers to the species that spins the silk, not to a quality level.

Is mulberry silk real silk?

Yes. It is the best-known silk, from the domesticated silkworm. EU law defines silk as fiber obtained exclusively from silk-secreting insects, whatever the species.

Where does mulberry silk come from?

From the cocoons of Bombyx mori, a silkworm domesticated in China at least 5,000 years ago. It no longer exists in the wild: it is raised on farms, and each cocoon is one continuous thread.

Is all silk mulberry silk?

No. There are more than 500 species of wild silkworms, a few of which are used for cloth: tussah, muga, eri. A label that just says "silk" doesn't name the species.

What is the difference between 100% silk and mulberry silk?

"100% silk" tells you the fiber is silk, not which worm made it. Look for "100% mulberry silk": that label names the fiber and the species, Bombyx mori.

What is the difference between mulberry silk and tussah silk?

The worm and the thread. Mulberry silk comes from Bombyx mori, as one continuous thread 10 to 24 micrometers thick. Tussah comes from Antheraea moths, with a thread 50 to 70 micrometers thick, often cut when the moth leaves the cocoon: tougher, rougher, harder to dye.

Why is mulberry silk better than wild silk?

Its thread is finer and more even: at least twice as fine as a tussah thread, and one continuous filament. That means softness, and silk that is easier to dye. Not strength: under tension, the thicker tussah does better.

Is mulberry silk the same as satin?

No. Mulberry silk is a fiber; satin is a weave, and it can be silk or polyester. A label that only says "satin" tells you nothing about the material.

What does grade 6A mean?

It is the highest grade sellers advertise for raw silk thread, rated on evenness and defects. It applies to the thread, not to the finished fabric, and it is declared by the supply chain: as far as we know, there is no public database to check it on a product.

What does 22 momme mean?

It is the fabric's weight: 22 momme is about 95 grams per square meter. Higher momme means heavier fabric, but the number only compares between fabrics of the same weave.

Why is mulberry silk expensive?

The silkworm only lives on farms, the thread is reeled cocoon by cocoon, and degumming removes the sericin, 20 to 25% of the raw thread's weight. Price alone proves nothing, though: check the label and the momme.

Is mulberry silk vegan?

No. It is an animal fiber, and conventional sericulture kills the silkworm at the pupal stage (Wikipedia, "Bombyx mori"). So-called Ahimsa silk is a wild silk made from the cocoons of wild and semi-wild silk moths (Wikipedia, "Silk").

Is mulberry silk antibacterial?

Nothing we have read shows that it is. An OEKO-TEX number attests the absence of harmful substances, not an antibacterial effect. Silk needs washing like any fabric worn against the skin.

How can I tell if silk is real mulberry silk?

Read the label ("100% mulberry silk"), find the momme and weigh the piece if it is a pillowcase, then burn-test one thread: silk ash smells like burnt hair, polyester leaves a hard black residue. The burn test can't tell mulberry from tussah.

Sources

• Wikipedia: Silk, Bombyx mori, Wild silk, Charmeuse, Units of textile measurement, consulted on November 2, 2026.
• FAO, chapter 11, raw silk testing and classification.
• French Wikipedia, Soie, for the burn test.
• Review PMC12926875 (2026), table 2; study PMC12940948 (2026) on artificial diet.
• EU Regulation 1007/2011 on textile fiber names, EUR-Lex.
• Wiktionary, for the etymology of "silk".

→ See the Noctya 22 momme mulberry silk sleep mask