Silk Education
Mulberry Silk Grading Explained: 6A vs 5A vs Charmeuse vs Momme
9 min read · written for Wildfool by hand
Mulberry silk is graded by cocoon length, strand purity, and luster — three measurements taken to two decimal places at the mill, and almost never explained on the label. The terms you see — 6A, 5A, charmeuse, 22 momme — each describe a different layer: the cocoon, the weave, the weight. Once you know which is which, the same hangtag stops being decoration and starts being a spec sheet.
In sixty seconds
- Mulberry silk comes from Bombyx mori silkworms fed white mulberry leaves. Each cocoon yields a continuous filament up to 1,500 meters long.
- Grades from 6A to F describe the raw silk fiber: strand length, evenness, color uniformity. 6A makes up roughly two percent of annual world production.
- Momme is the weight unit. 1 momme = 4.34 grams per square meter. 12-16 mm is light; 19-22 is the bedding standard; 30+ is heavy drape.
- Charmeuse, habotai, and twill are weave types, not grades. A 22-momme charmeuse and a 22-momme habotai are the same weight woven differently — and they fall and shine differently.
- Suzhou — not Hangzhou — has been the historical center of fine Chinese silk for nearly five thousand years. The Yangtze River Delta climate is what makes the silk possible.
What mulberry silk actually is
Mulberry silk is the product of one specific insect — Bombyx mori, the domestic silk moth — fed exclusively on the leaves of one specific tree, Morus alba, the white mulberry. The relationship is unusual. Sericulture has been documented in China for at least five thousand years, and the moth has been domesticated for so long that Bombyx mori no longer flies and depends entirely on humans for survival.
The silk itself is a continuous single filament, secreted from the silkworm's salivary glands as it spins its cocoon. The cocoon protects the pupa during metamorphosis, and the filament inside it can reach 1,500 meters in length — close to a mile of unbroken thread per cocoon. Most other "silk" — wild silk, tussah, eri, muga — comes from different moth species, often spinning shorter, coarser, irregular fibers. Mulberry silk is the long-strand benchmark against which the others get measured.
The composition matters for what silk feels like on skin. Roughly 75 to 83 percent of the raw fiber is fibroin, the structural protein that gives silk its strength and luster. The remaining 17 to 25 percent is sericin, a sticky protein that originally cohered the strands of the cocoon and is mostly removed during processing. What's left in the finished fiber is silk's signature — a long, smooth filament with a triangular cross-section that reflects light in a particular way.
The grade scale: 6A, 5A, 4A, 3A
Mulberry silk is graded against an international standard developed by the International Silk Association after World War II, refined in China's GBT 1797-2008 Raw Silk Quality Standards into eleven tiers: 6A, 5A, 4A, 3A, 2A, A, B, C, D, E, and F. Most consumer-facing labels use only the top four.
- 6A — the longest, cleanest, strongest filaments. Pearly white, uniform color, minimal defects. Roughly two percent of global mulberry silk production hits this tier.
- 5A — very good fiber, with measurable but small differences from 6A in uniformity and consistency. Most quality silk bedding sold under high-grade labels is 5A.
- 4A — solid mid-range silk. Clean enough for most apparel, with slightly more variation in color and slightly shorter average strand length.
- 3A and below — used in blends, accents, and lower-priced silk products. Strand length drops, defects rise.
Three things determine the grade:
- Strand length and continuity. Long, unbroken filaments are stronger and produce smoother fabric. Grade C and lower come from the innermost layers of the cocoon, where strands are short and thin.
- Strand evenness. Variations in thickness across the length of a single filament reduce the grade. The smoothest silk has uniform thickness end to end.
- Color and luster. Top-grade silk is pearly white before any dye is applied. Yellower or grayer raw silk indicates contamination during processing or species variation — both downgrade the lot.
The grade describes the raw silk before it's woven. A bedsheet labeled "6A mulberry silk" is making a claim about the input fiber, not necessarily the final fabric. Two finished products with the same 6A label can feel quite different, depending on how the fiber is woven and finished.
Momme weight: how heavy is heavy enough?
Momme (pronounced "mom-ee") is the unit of weight for silk fabric, the way thread count is the unit for cotton. One momme equals 4.34 grams per square meter. Eight momme is approximately one ounce per square yard.
The momme number tells you how heavy the silk is — and by extension how it drapes, how opaque it is, and how it ages.
| Momme | Hand-feel | Common use |
|---|---|---|
| 6–8 | Whisper-light, semi-sheer | Chiffon, very fine scarves |
| 12–16 | Light, fluid | Habotai, crepe de chine, blouses |
| 16–19 | Medium, structured | Twill scarves, heavier blouses |
| 19–22 | Substantial, drape-heavy | Sleep masks, pillowcases, statement scarves |
| 22–25 | Bedding-grade, heavy drape | Sheets, robes |
| 30+ | Dense, almost stiff | Heavyweight charmeuse, special-finish scarves |
Twenty-two momme is the most common reference point because it's the bedding standard. Below that, the silk reads as fine or lightweight against skin; above that, it starts behaving like a heavier fabric — closer to wool's weight class than to silk's classic ethereal feel. There's no universal right momme. A 12-momme silk twill scarf knots loosely and falls beautifully across the collar; a 22-momme silk twill of the same dimensions doesn't knot the same way. Heavier isn't better. Heavier is different.
Grade describes the cocoon. Momme describes the weight. Weave describes the structure. A silk hangtag that names all three is telling you what it is. A hangtag that names none of them is asking you to trust it.
Charmeuse, habotai, twill — the weave layer
Grade and momme describe the fiber and weight. The weave is a third layer entirely.
- Habotai. Plain weave — over-under-over-under. Same look on both sides. Lightweight, crisp, balanced sheen. The most common silk for scarves, linings, and beginner sewing. Less expensive than charmeuse at the same momme weight.
- Charmeuse. Satin weave — warp threads float over multiple weft threads, creating long surface stretches. Glossy, drapey, slippery front; matte back. Catches light dramatically. Drapes over the body almost without resistance — which is why it's the silk of slip dresses, pillowcases, and sleep masks.
- Twill. Diagonal weave structure, the same construction principle as denim but in silk. Smooth surface with a subtle diagonal grain visible at the right angle. Less fluid than charmeuse, more substantial, takes prints beautifully. The classic Hermès carré is silk twill.
- Satin (umbrella term). Charmeuse is one form of satin weave; duchesse satin and slipper satin are others, at heavier momme weights and stiffer hand-feels. "Satin" without qualification usually means a non-silk fiber woven the same way; "silk satin" usually means charmeuse.
The takeaway: a "22-momme silk charmeuse" tells you weight, fiber type, and weave together, and that's enough to predict drape and hand. "100% silk" alone doesn't.
Care, in three rules
Hand-wash in cool water with a silk-specific or mild wool detergent. Strong detergents and hot water break down the fiber. Lay flat on a clean towel to dry. Never wring.
Skip direct sunlight. Silk yellows and weakens under prolonged UV. The same 6A bedsheet can fade to ivory after a few seasons by a sunny window.
Skip the dryer. Heat from a tumble cycle damages silk faster than almost any other natural fiber. Silk that's been through a hot dryer cycle loses its luster permanently. If a stain comes in, blot rather than rub, and take any structural stain (oil, ink, makeup) to a dry cleaner that handles silk specifically.
The Wildfool silk: woven in Suzhou
Wildfool's silk is woven in Suzhou — the city in Jiangsu province that has been the historical center of fine Chinese silk for nearly five thousand years. Archaeologists in 1958 found silk fragments in Wuxing County near Taihu Lake dating to the Neolithic era — among the earliest evidence of silk anywhere in the world. By the Tang and Song dynasties, Suzhou had become China's silk capital. By the Ming and Qing, official Suzhou workshops supplied the imperial court.
The Yangtze River Delta climate is what makes Suzhou silk possible: temperate, humid, with the abundant rainfall that mulberry trees need. The silk itself comes from the same mills that supply parts of the European heritage trade — including the houses whose names appear on the label of a four-figure scarf.
The current Wildfool silk line lives at /collections/scarves. Priced for the material.
Frequently asked
Is a 6A silk bedsheet always better than a 5A one?
Not always. 6A describes the raw fiber input. The same fiber, woven and finished differently, can produce a 6A sheet that feels identical to a well-made 5A — or worse than a finely woven 4A. Grade is one variable; weave, momme, and finish are the others.
What's the difference between mulberry silk and "regular" silk?
Mulberry silk comes from Bombyx mori silkworms fed exclusively on white mulberry leaves. The fiber is long, even, and pearly white — the benchmark for all other silk types. "Regular silk" usually means tussah, eri, or muga silk from wild moths; those fibers are shorter, often coarser, and sometimes naturally beige or brown.
Does momme matter for scarves?
Yes, but the right momme depends on use. A 12-momme silk scarf knots loosely and drapes lightly across the collar — the typical breezy summer scarf. A 16-19 momme silk has more structure and holds a knot. A 22+ momme silk feels closer to a wrap than a scarf.
Is charmeuse always silk?
No. "Charmeuse" describes a satin weave structure that can be made from silk, polyester, rayon, or other fibers. "Silk charmeuse" is the silk version. Synthetic charmeuse can imitate the appearance of silk charmeuse but doesn't share its breathability, temperature regulation, or aging behavior.
Can I machine-wash silk?
Some modern silk pieces are labeled machine-washable on a delicate cycle in cold water. Most aren't — agitation breaks down the fiber's smooth surface, and silk emerges from a hot or rough wash with permanent damage. The label is the authoritative source. When in doubt, hand-wash.
Is Suzhou silk different from Hangzhou silk?
Both cities are in the Yangtze River Delta, both have long silk histories. Suzhou is the older and more prestigious center for fine silk fabric — silk fragments excavated near Taihu Lake date the local craft to nearly five thousand years ago, and the imperial workshops of the Ming and Qing eras were Suzhou-based. Hangzhou is more commonly associated with the broader silk industry — merchants, garment production, court supply. The fiber and craft tradition are similar; the names mark different cities.
Silk rewards a precise vocabulary. Once you know which word describes the fiber, which describes the weight, and which describes the weave, a hangtag stops feeling like marketing and starts feeling like information.