Silk Grading System Explained: What 6A Actually Means

Few shopping experiences are more humbling than trying to buy a silk pillowcase and running headlong into terms like 6A, 5A, mulberry, charmeuse, and 22 momme. Each term sounds authoritative. None of them is self-explanatory. And the relationship between them is almost never explained on the product page.

This guide untangles the silk grading system from the ground up: where it originated, what each grade level actually signals, what it cannot tell you, and how to use it as one part of a smarter buying decision. By the end, you will be able to read any silk pillowcase product page and know within seconds whether the brand is being genuinely transparent or hiding behind marketing shorthand.

Why Silk Grading Confuses Almost Everyone

The confusion starts with a reasonable assumption: that "grade" works like a score on a finished product. It does not. The grading system for silk was never designed with pillowcase buyers in mind. It was developed for the raw silk industry, where manufacturers, traders, and fabric mills needed a standardised way to describe and price raw filaments before those filaments were ever woven into cloth.

By the time a silk grade label appears on a consumer product, it has already travelled through several stages of transformation: cocoon, raw filament, reeled silk, woven fabric, cut and sewn pillowcase. The grade label tells you something about the very first stage. It tells you almost nothing about the final one.

The second source of confusion is that multiple grading systems exist simultaneously. China, Japan, and the International Silk Association (ISA) each developed their own classification tables. These systems do not all agree on the top grade or even the number of grade levels. Brands regularly pick whichever label sounds most premium, regardless of which system it comes from.

Where the Grading System Actually Came From

Raw silk grading developed in the nineteenth and early twentieth centuries as sericulture (silkworm farming) became an internationally traded commodity. Japan, China, and Italy were the dominant producers, and export markets needed a shared language to negotiate price and quality without physically inspecting every shipment.

The International Silk Association codified a system that graded raw silk primarily on the regularity and diameter consistency of the filament. Silk filaments are natural protein fibres produced by Bombyx mori silkworms: because each cocoon is spun slightly differently, the diameter of the filament varies along its length. Lower grades have more variation. Higher grades have filaments that are more uniform, cleaner, and freer from defects like knots, broken ends, and hairiness.

This was an industrial quality control system for a bulk commodity. It was precise, reproducible, and completely irrelevant to the pillow lying under your head. But the language migrated from trade catalogues into consumer marketing because it sounded technical and therefore trustworthy.

What 6A, 5A, 4A and Lower Grades Actually Mean

Under the Chinese national standard GB/T 1797-2008, raw silk is assessed on five primary quality indicators. The grade assigned is determined by whichever indicator scores lowest, meaning a filament must perform consistently well across all measures to achieve the top grade. The five indicators are:

• Size deviation: how closely the filament diameter matches the declared specification.
• Maximum size deviation: the worst single departure from specification across the sample.
• Evenness change: how consistently the filament maintains its diameter along its length.
• Cleanness: freedom from attached sericin, loops, and surface debris.
• Neatness: absence of defects such as knots, split ends, and hairiness.

The highest achievable grade under this system is 6A. It requires the filament to meet or exceed the threshold for all five indicators simultaneously. This is genuinely difficult to achieve at scale, which is why 6A filament is rarer and commands a higher price in the raw silk market.

It is worth noting that the ISA system, which many Western brands still reference, tops out at 4A. A brand claiming 6A is implicitly referencing the Chinese standard. There is nothing wrong with that, provided the claim is verifiable.

Grade Comparison Table: What Each Level Means for Shoppers

What Grade Does Not Tell You

This is the section most product pages skip entirely. Grade describes a property of the raw filament. A finished pillowcase is the product of at least four additional decisions, none of which are captured by a grade label.

Momme weight

Momme is the unit used to describe silk fabric weight and density. One momme equals 4.340 grams per square metre. A 22-momme pillowcase is denser, heavier, and more durable than a 16-momme one. The grade of the underlying filament and the momme weight of the woven fabric are entirely independent variables. You can weave 6A filament into a 12-momme cloth or a 30-momme cloth. The momme weight affects durability, drape, and the tactile experience far more directly than the filament grade alone. For more on this, see our full guide to momme weight in silk.

Fibre content

Grade tells you nothing about whether the fabric is 100% silk or a blend containing polyester, viscose, or other fibres. A "6A" claim on a blended product is misleading at best. Always check for explicit confirmation that the fibre content is 100% mulberry silk.

Weave type

Silk can be woven in several ways. Charmeuse is the most common weave for pillowcases: it has a smooth, glossy face and a matte reverse, created by a satin float weave structure. This is distinct from "satin," which describes a weave pattern that can be applied to any fibre, including polyester. A charmeuse weave from high-quality silk filament produces a different hand feel and durability profile than the same filament woven in a plain or twill structure. The grade label does not specify any of this. See our guide to charmeuse vs satin fabric for the full breakdown.

Stitching and construction

Seam quality, edge finishing, and closure type (envelope vs. zip) determine how the pillowcase wears over months of washing. A poorly stitched 6A pillowcase will unravel or pucker at the seams long before a well-made 5A one does.

Safety certification

Grade says nothing about the dyes, finishing chemicals, or processing aids used during production. A pillowcase can be made from top-grade silk filament and still contain residual chemical traces from industrial processing.

How Grade Interacts With Momme Weight

One of the most useful things to understand about silk grading is that grade and momme weight are orthogonal: they measure entirely different things and can be combined in any combination. A 6A-grade filament can be woven into a 12-momme fabric or a 30-momme fabric. The grade of the filament affects the smoothness and uniformity of the raw material going into the loom. The momme weight determines how densely that material is woven and therefore how heavy, durable, and substantial the final cloth is.

In practical terms: if a brand claims 6A silk but does not state the momme weight, you are missing half the quality picture. The two numbers work together. Expert consensus and independent testing suggest that for a pillowcase intended for regular use, a momme weight between 19 and 25 sits in the optimal range.

Below 19 momme, fabrics tend to feel thin and may not hold up to repeated washing. Above 25 to 30 momme, fabrics become luxuriously dense but command a significant price premium. For most people, a 22-momme pillowcase in 100% mulberry silk is the considered midpoint: substantial enough to last, smooth enough to deliver the low-friction surface that benefits hair and skin. For those who want the maximum weight and durability, a 30-momme option offers a noticeably denser, more structured drape. Read more in our complete momme count reference guide.

Mulberry Silk and Weave Type: The Two Factors That Sit Above Grade

For a pillowcase specifically, two factors matter more than filament grade in determining the end experience: fibre type and weave construction.

Why mulberry silk is the benchmark

Mulberry silk comes from Bombyx mori silkworms raised exclusively on white mulberry leaves under controlled conditions. This controlled diet produces filaments that are longer, rounder in cross-section, and more consistent in diameter than those from wild or tussah silkworms. The result is a fabric with higher natural lustre, a smoother hand feel, and greater protein fibre integrity.

Other silk types exist: tussah (wild silk), eri silk, and muga silk each have distinct properties. They are not inferior in all contexts, but for the specific application of a pillowcase designed to minimise friction on hair and skin, the uniformity and smoothness of mulberry silk filaments give it a measurable advantage. To understand mulberry silk in more depth, see what is mulberry silk.

Charmeuse weave: why it matters for pillowcases

Charmeuse is a lightweight satin-weave fabric: the majority of warp threads float over multiple weft threads, creating a smooth, reflective face. This structure maximises surface smoothness, which is precisely what makes silk pillowcases beneficial for hair and skin. The matte reverse side is woven tighter and provides the structural stability of the pillowcase.

A silk pillowcase described as "satin weave" or "charmeuse" is using a specific and meaningful technical descriptor. "Satin" without a fibre declaration could mean polyester, so always confirm both the weave type and the fibre content are stated explicitly.

Can a 5A Pillowcase Outperform a 6A One? Yes, and Here Is Why

The short answer: construction quality determines daily performance more consistently than filament grade. Here is a concrete example of how this plays out.

Imagine two pillowcases. The first is made from 6A-grade mulberry silk filament woven to 16 momme, with loosely finished seams and a minimal edge treatment. The second uses 5A-grade filament woven to 22 momme in a tight charmeuse structure, with reinforced seams and a clean envelope closure.

The second pillowcase will feel heavier and more substantial. Its tighter weave will produce a smoother surface. Its seams will survive more wash cycles. Its weight means less shifting on the pillow during the night, which reduces friction further. The 6A filament in the first pillowcase is of marginally higher intrinsic quality, but the construction decisions have erased that advantage entirely.

This is the central argument against treating grade as the dominant purchasing signal. It is a useful indicator of raw material quality, but it sits at the beginning of a long production chain. Every step after the filament is reeled adds or subtracts from the finished experience.

How to Spot Inflated or Fake Grade Claims

Because silk grading is not universally regulated in consumer markets, grade claims are easy to inflate. There is no central authority verifying that a pillowcase sold as "6A" was tested under GB/T 1797-2008 protocols. Here are the warning signs that a grade claim may be unreliable.

No third-party certification to back it up

A grade claim without any independent certification is self-reported. The brand is telling you its own product is excellent. A credible brand pairs its grade claim with OEKO-TEX STANDARD 100 certification, which is issued by an independent testing institute and verifiable by certificate number.

Grade claim with no momme declaration

Any brand genuinely committed to transparency will state the momme weight explicitly. If the product page leads with "Grade 6A" but buries or omits the momme weight, the grade claim is being used to distract from a lower-weight fabric.

Vague "premium" or "luxury" language with no technical specifics

Authentic quality claims are specific. "100% mulberry silk, Grade 6A, 22 momme, OEKO-TEX certified" is specific. "Premium luxury hotel-grade silk" is not. If every adjective is a marketing word rather than a technical term, read carefully.

No fibre content declaration

If the product description does not state explicitly that the fabric is 100% silk (or 100% mulberry silk), there may be a blend involved. Grade claims on blended fabrics are effectively meaningless.

Very low price for a stated high grade

6A mulberry silk filament is expensive. 22 to 30 momme adds more material cost. A pillowcase set claiming 6A, 22 momme, 100% mulberry silk at a price that seems too good is almost certainly either lower grade than claimed, lower momme than stated, or a blend.

OEKO-TEX STANDARD 100 Explained: Why It Matters Alongside Grade

OEKO-TEX STANDARD 100 is an independent certification from the Oeko-Tex Association, a consortium of 18 textile research and test institutes across Europe and Japan. It tests every component of a finished fabric, including threads, buttons, and dyes, for over 100 harmful substances, including pesticide residues, heavy metals, formaldehyde, and pH levels.

The key distinction from a grading claim is that OEKO-TEX certification applies to the finished product, not the raw material. A pillowcase can be made from perfectly graded 6A filament and still carry dye residues or processing chemicals unless the finished fabric has been independently tested. Conversely, an OEKO-TEX-certified pillowcase has been verified to meet safety standards at every stage of production.

For context: silk is a natural protein fibre (fibroin), but it is processed with sericin degumming agents, dyes, and finishing treatments before it reaches you. High filament grade does not guarantee those processes were clean. OEKO-TEX does.

The certification number on an OEKO-TEX label is publicly searchable at the OEKO-TEX website, which means you can verify the claim directly. If a brand cites OEKO-TEX but does not provide the certificate number, ask for it.

What Else Matters Besides Grade

By now the picture is becoming clearer: grade is a meaningful but narrow data point. The full quality picture of a silk pillowcase requires you to look at five things simultaneously.

Fibre type. Is it 100% mulberry silk? Is that stated explicitly, not just implied by "natural silk" language?

Momme weight. Is it clearly stated? Is it in the 19 to 25 range for a pillowcase, or higher for a premium option? See our guide to 30-momme silk pillowcases if you are considering a heavier weight.

Weave. Is it charmeuse or a similar smooth-face satin weave? Is the weave type stated at all?

Construction. Are seams finished? What is the closure type? Is the stitching described with any specificity?

Certification. Is there an OEKO-TEX STANDARD 100 certification with a verifiable number?

A brand that answers all five clearly is a brand that has nothing to hide. One that leads with grade and omits the rest is selling a story, not a specification.

Your Complete Buying Checklist: Grade Plus Everything Else

Use this checklist before purchasing any silk pillowcase. Every item should be answerable from the product page without having to contact customer support.

How to Read a Silk Pillowcase Product Page Like an Expert

Most product pages are written to create an impression of quality rather than to provide a complete technical specification. Once you know what to look for, the gaps become obvious.

Start with fibre content, not the headline claim

Scroll past the marketing copy to the product specifications or description. Find the fibre content statement. If it says "100% mulberry silk", you are in the right territory. If it says "mulberry silk blend", "silk-feel fabric", or simply "satin", close the tab.

Look for momme weight in the specs, not the title

Many brands bury or omit momme weight because it reveals that a product is lighter than competitors. If momme weight is not in the specifications table, search the full description. If it is nowhere, that is a red flag.

Check the grade claim for a referenced standard

A credible grade claim cites the standard it is assessed against. "6A" alone is a marketing assertion. "Grade 6A per GB/T 1797-2008" is a technical claim that could in principle be verified.

Find the certification number

OEKO-TEX certification should be listed with a certificate number. Visit the OEKO-TEX website and search for it. If the number is not provided, or if searching it returns no result, the certification claim is unverified.

Read the care instructions

Genuine silk requires careful laundering. If care instructions say "machine wash any temperature" or make no mention of delicate handling, the product may not be real silk.

Assess the price against the specification

A genuine 6A, 22-momme, OEKO-TEX-certified 100% mulberry silk pillowcase costs more than a well-made cotton pillowcase. If the price seems far below what the specification would justify, apply additional scrutiny to every claim.

The Honest Take: Is Grade Marketing or Is It Meaningful?

Both. Grade is a meaningful technical descriptor of raw filament quality. It is also frequently deployed as a marketing shorthand that implies more than it delivers. These two things are not contradictory.

6A filament is genuinely better than 4A filament as a raw material. All else being equal, a product made from 6A filament will be smoother, more consistent, and more lustrous. The problem is that all else is rarely equal. Brands that invest in top-grade filament sometimes cut costs elsewhere: lower momme weights, cheaper finishing treatments, looser construction, absent certifications. The grade headline obscures these trade-offs.

The most useful mental model is this: grade sets a ceiling on potential quality. Everything else determines how close the finished product gets to that ceiling. A well-made 5A pillowcase at 22 momme with OEKO-TEX certification is closer to its ceiling than a poorly made 6A pillowcase at 16 momme with no certification. You want both the high ceiling and the skilled construction to reach it.