What Silk Grades Actually Mean (And Where the System Breaks Down)
Shop for silk long enough and you'll run into grading claims — "6A silk," "Grade A mulberry silk," "top grade." These labels sound authoritative, but the system behind them is looser than most product pages suggest. Here's what silk grading actually measures, and what it doesn't.
There's No Single Global Grading Standard
Unlike diamonds or wool, silk has no universal, independently regulated grading body that every manufacturer reports to. The most commonly cited system — the "A" through "6A" scale — originated in the Chinese silk industry as an internal quality classification for raw silk fibre and yarn, not finished fabric. It's widely used across the industry, but it isn't enforced or audited by a single global authority, which means grading claims are largely self-reported by manufacturers and suppliers.
This matters because "6A grade" on a product listing is a claim, not a certification. There's no universal inspector checking the fabric against a fixed rulebook before that label goes up.
What the Letter-Number System Measures
Where the grading scale is used consistently, it typically evaluates raw silk yarn against a few technical criteria before weaving:
- Fibre length and continuity — longer, unbroken filaments produce smoother, stronger yarn
- Uniformity — consistency in thread thickness across a single strand
- Surface cleanliness — the absence of slubs, knots, or impurities in the raw fibre
- Luster — how evenly the fibre reflects light, which affects sheen once woven
Grades run from lower (more irregularities, shorter fibres) to 6A (longest, most uniform, cleanest fibre). In theory, higher grades should correlate with stronger, smoother, more consistent fabric.
Where Grading Breaks Down
The scale evaluates raw yarn, not the finished textile. A high grade of raw silk can still be woven poorly, finished with harsh chemical processes, or dyed in ways that damage the fibre after the "grade" was assigned. Conversely, a well-woven fabric from mid-grade fibre can outperform a poorly finished fabric that started with 6A yarn. Grade is an input quality marker, not a guarantee about the product you're actually holding.
There's also no penalty for overstating it. Because no external body audits most grading claims on consumer listings, "6A" has become something close to a marketing default — attached to products regardless of whether the raw fibre was independently verified.
Mulberry vs. Non-Mulberry: A Separate Question From Grade
Grade and silk type are often conflated, but they answer different questions. Silk type refers to the species of silkworm and its diet — mulberry silkworms (Bombyx mori) are fed exclusively mulberry leaves in a controlled environment, producing a more uniform, finer filament than wild or "tussar" silk varieties, which come from silkworms with varied diets and less controlled rearing. Mulberry silk is generally the higher baseline for consistency before grading even applies. A grading number attached to a non-mulberry silk isn't measuring the same starting material as one attached to mulberry silk, even if the number looks identical on paper.
What to Check Instead of the Grade Letter
Since grade claims are largely unverifiable from a product listing alone, a few other details tell you more:
- Silk type — confirm it's mulberry silk specifically, not just "silk" or "silk blend"
- Momme weight — a measurable, weight-based spec (16–19mm is standard for sleepwear) that's harder to inflate without changing the physical fabric
- Weave — satin, charmeuse, and crepe satin behave differently even at identical momme and grade
- How it holds up in hand — even weave, minimal slubbing, and consistent sheen across the fabric are things you can actually assess yourself, regardless of what letter is on the label
A grade claim is a starting point for a conversation, not proof on its own. The measurable specs — fibre type, momme, weave — hold up to scrutiny in a way a self-reported letter grade doesn't.