Mulberry silk bedding is often sold as “22 momme, 6A grade”—two numbers that sound like a single quality score. They measure different things: momme is fabric weight per unit area; 6A is a filament length and defect grading convention used in raw silk trading. Treating them as interchangeable leads to spec sheets that look precise but do not predict hand-feel, durability, or whether the labeled composition holds up in testing.
Why the labels get conflated
Export listings and hang tags routinely stack momme and letter-grade on one line. In practice:
- Momme (mm) describes how heavy the woven silk is—grams per square meter scaled by a silk-industry convention (1 momme ≈ 4.340 g/m² for silk). Higher momme usually means thicker yarn packing or heavier weave, not automatically better cocoon grade.
- 6A (or 5A, 4A…) comes from cocoon/filament sorting: longer, cleaner filaments with fewer breaks score higher. It is assigned to raw silk lots before weaving, dyeing, and finishing reshape the final article.
A duvet shell at 22 momme may be woven from 6A filament, but momme does not prove 6A—and 6A raw silk can be woven at 16 momme or 30 momme depending on product target. The confusion matters when a lighter 19 momme sheet is rejected because the spec assumed “6A must feel heavy.”
What momme actually changes in bedding
Momme is a density proxy for woven silk, comparable in role to GSM for cotton—not a softness grade.
- 16–19 momme — typical for charmeuse pillowcases and sheet faces; more drape, faster dry time, lower volumetric weight for freight.
- 22–25 momme — common for premium shams, duvet covers, and box-wall comforter shells; higher abrasion resistance, more body in the hand.
- 30+ momme — specialty or upholstery-weight silks; rare in bulk bedding SKUs because cost and loft trade-offs rise quickly.
Weave structure shifts the feel at the same momme: a 22 momme plain-weave habotai reads lighter than 22 momme satin because yarn float length and thread count differ. Momme alone does not specify weave—only weight after finishing.
How 6A grade is used in the supply chain
Letter grades (6A top, stepping down to 3A/4A/5A depending on market) summarize filament metrics at the raw silk auction or reel stage:
- Filament length — longer continuous filaments mean fewer splices in fine yarn, smoother surface after reeling.
- Defect count — neps, thick/thin places, and broken filaments lower the grade.
- Reeling uniformity — consistent denier across the hank supports even dye uptake later.
After degumming, twisting, dyeing, and calendering, the grade of the original hank is not re-tested on the finished duvet. “6A” on a retail tag is often trade shorthand for top-tier mulberry, not a certificate tied to that bolt. Lab verification uses composition and fiber identification, not momme.
Reading specs without equating momme and grade
Useful product documentation separates the layers:
Declare each dimension explicitly
- Composition — “100% mulberry silk” with fiber content by weight; specify if warp/weft differ.
- Finished momme — measured on the delivered fabric after pre-shrunk finishing, not greige.
- Weave — charmeuse, habotai, twill; affects hand-feel more than a one-point momme shift.
- Raw-silk grade reference — if claimed, tie to supplier COA for the yarn lot, not the SKU name.
Tests that answer different questions
- Fiber ID (microscopy / ISO 17751) — confirms mulberry vs tussah vs synthetic blends; unrelated to momme.
- Weight per unit area — validates momme on the bolt you will cut.
- Colorfastness and dimensional change — finishing quality; a 6A yarn poorly scoured can still fail wash tests at any momme.
Momme and grade: what each predicts (indicative)
| Parameter | Measures | Does not measure |
|---|---|---|
| Momme (finished fabric) | Weight density, bulk freight impact, abrasion margin | Cocoon grade, filament length, silk purity |
| 6A raw-silk grade | Filament length/defects at reeling | Finished momme, colorfastness, shrinkage |
| Charmeuse vs habotai at 22 momme | Weave-driven drape and luster | Either parameter above, unless tested separately |
For comforter shells, 22 momme charmeuse is a common premium anchor point: enough body for shell durability without the stiffness of 30+ momme upholstery silks. The grade of yarn underneath still needs its own traceability if “6A” appears on the product spec.
Takeaway
Twenty-two momme and 6A grade answer different questions—fabric weight after finishing versus raw filament quality before weave. Sound bedding specs list composition, finished momme, weave, and finishing (pre-shrunk, dye class) as separate fields. When documentation stacks both on a single line without weave or finishing detail, the fix is clearer spec fields and targeted tests, not assuming a higher momme automatically means a higher cocoon grade or a softer hand.
