Grade 6A and IFTH: Decoding Silk Labels

6A. 19 momme. OEKO-TEX. IFTH. Silk product sheets sometimes look like a coded score — and I’m often asked what to really make of them. I spend my days with my hands in fabrics; let me share my decoding key, the one that distinguishes true mulberry silk from a pretty word on a label.

In short:

• The grade (from A to 6A) rates the quality of the raw fiber: length, consistency, and cleanliness of the thread.
• The momme measures the weave density: it describes the feel, drape, and durability of the fabric.
• OEKO-TEX Standard 100 certifies the absence of harmful substances; independent labs like IFTH verify a fabric’s composition.
• No label replaces the tag: demand “100% mulberry silk” and a clearly stated momme weight.

Why are these labels so confusing?

Because they don’t refer to the same thing. The grade assesses the fiber before weaving, the momme weighs the finished fabric, and certifications verify its safety or composition. No single global standard covers everything: the grade, in particular, is declared by the silk mills themselves. That’s exactly why an expert eye always cross-checks several indicators rather than relying on a single label.

Grade 6A: what it really says about the fiber

Raw silk — the thread unwound from cocoons before weaving — is classified by grades from A to 6A. 6A represents the top of the scale: the longest and most consistent fibers, unwound from whole and intact cocoons.

Specifically, a grade 6A thread is recognized by:

• its length: a continuous thread, producing a smooth fabric without repairs or pilling;
• its consistency: a constant diameter, ensuring even weaving and uniform luster;
• its purity: very few impurities and a naturally clear shade, which beautifully takes color;
• its strength: a long fiber breaks less, and the fabric ages better.

Keep in mind, however, that this classification is not audited by a central body. A "6A" only has value at a place that pairs it with a specific momme and verifiable checks.

Momme: the other figure, often more telling

Momme is a weight unit inherited from Japan: about 4.34 g/m². The higher it is, the denser the weave — the more the fabric has body, drape, and the longer it will last. In my eyes, it is the most honest figure on a product sheet because it can be verified on a scale.

I dedicated an entire guide to this question: which silk weight to choose depending on the use.

OEKO-TEX, IFTH: what the certifications guarantee

The OEKO-TEX Standard 100 certification attests that a textile has been tested against a long list of undesirable substances. Each certificate has a number that can be verified online — a logo without a number is just a drawing.

The IFTH (French Institute of Textile and Clothing) is an independent laboratory: it is entrusted with composition analyses — confirming that a fabric is truly 100% silk — and physical tests. This type of analysis protects against the most common market confusion: "silk satin" which is actually polyester woven in satin.

Keep in mind the limit of this exercise: these checks guarantee safety and composition, never the beauty of a fabric. They rule out counterfeits; they do not replace grade, momme, or feel.

Real silk or "satin": my simple checks

Remember first that satin refers to a weave, not a material: there is silk satin as well as polyester satin. When looking at a label, I check three things: the exact composition ("100% mulberry silk," not just "satin"), the presence of a stated momme, and price consistency — dense mulberry silk cannot cost the price of polyester.

To the touch, real silk feels cool at first then adjusts to your temperature; its luster is soft, changing with the light, whereas polyester shines uniformly, almost plasticky.

My checklist before buying

1. Composition: "100% mulberry silk," black on white.
2. Specified momme, suited to the use (from 16.5 to 30).
3. Stated grade — 6A for the finest fibers.
4. Verifiable certification, with number.
5. Serious care advice — real silk deserves careful washing, and an honest source will tell you so.

This is the standard StudioSoie applies when selecting its 6A grade mulberry silks, from 16.5 to 30 momme, for bedding as well as clothing. Discover our mulberry silks — and read their sheets with your new expert eye.

— Colette, for the StudioSoie Journal

FAQ: silk labels and quality

What does "6A silk" mean?

It is the highest grade of raw silk: long, regular, and pure fibers, reeled from whole cocoons. It describes the fiber quality before weaving.

Grade and momme, what’s the difference?

The grade indicates the quality of the raw fiber; the momme measures the density of the woven fabric (about 4.34 g/m² per momme). A fine piece shows both.

What does OEKO-TEX Standard 100 guarantee?

That the textile has been tested against a list of undesirable substances. The certificate has a number that can be verified online.

How can you tell if a fabric is truly mulberry silk?

Read the composition ("100% mulberry silk"), look for a stated momme and verifiable certification. To the touch, the silk feels cool then warm, with a soft, changing luster.