That Yarn · Journal

What Does 'Superfine Wool' Really Mean?

Less than you might hope, and more than the marketing suggests. "Superfine" is a real grade with a real number behind it — but no two authorities draw the line in quite the same place.

"Superfine" is one of those words that sounds like a promise and behaves like a guess. On a yarn label it signals softness, refinement, something worn close to the skin. Ask where exactly the fineness begins, though, and the answer turns out to depend on who you ask.

This is not a flaw in the word. It is the honest situation, and understanding it makes you a better judge of wool than any single number could. Superfine is real, it is measurable, and it is worth wanting — but it is a band, not a boundary, and knowing that protects you from paying for a word that a label is free to define however it likes.

Fineness is measured in microns

Wool fineness is measured as fiber diameter, in microns — one micron being one-thousandth of a millimetre. It is measured by instrument, scanning thousands of fibers from a sample and reporting the average.

For scale: a human hair runs somewhere between 50 and 100 microns. The wool in a scratchy old jumper is around 30. Fine merino sits in the high teens. The whole meaningful range of apparel wool fits into a span of about fifteen microns, which is why single-micron differences matter so much.

The lower the micron count, the finer the fiber — and, usually, the softer it feels.

That word usually is doing quiet but important work, and we will return to it.

Where 'superfine' actually sits

Here is the part the word's confidence conceals. There is no single, universally agreed micron value at which fine wool becomes superfine. Different authorities place the line differently.

The pattern is clear enough to be useful. Superfine lives roughly between 15 and 18.5 microns, with most formal systems clustering the top of the band at 18.5. Below it, around 17.5 and finer, sits ultrafine. Above it, from roughly 18.6 to 20, sits fine merino.

Superfine is a band, not a boundary. When a label claims it, the useful question is not whether the word is allowed, but what micron number sits behind it. A stated 17.5 µm means something. The bare word "superfine" means whatever the seller wants.

Treat these as orientation. The boundaries between rows are conventions, and reasonable authorities shift them by a micron in either direction.

The word means two different things

Part of the confusion is that "superfine" travels between two industries that use it differently.

In knitting and yarn, it describes the raw fiber — the average diameter of the wool before it becomes anything.

In tailoring and suiting, the related "Super" numbers — Super 100s, Super 150s — grade the finished fabric, and are defined by maximum fiber diameter under IWTO rules. Super 100s permits wool up to 18.75 microns; Super 150s requires 16.25 or finer.

These are different systems for different products, and a number from one does not translate cleanly to the other. A yarn described as "superfine" and a suit labelled "Super 150s" are speaking related dialects, not the same language. Our guide to micron, S-count, and comfort factor works through how these grading systems relate — and where they don't.

Why 'finer equals softer' is only usually true

Now to that word we flagged. Fineness and softness are strongly related, but they are not the same thing, and treating them as identical is the most common mistake made about superfine wool.

Softness is governed less by the average diameter than by the proportion of coarse fibers in the mix — specifically those thicker than about 30 microns, whose stiff ends press into skin rather than bending against it. The textile-science consensus places the itch threshold around 22 microns for individual fibers; below it they bend, above it they prickle.

The consequence is genuinely counter-intuitive: two wools with the same average micron count can feel entirely different, because one has a tighter distribution than the other. A superfine wool with a wide spread can feel less soft than a fine wool with a narrow one. The average is not the whole story — the shape of the distribution is.

A stated micron count tells you the centre of the fiber. It does not tell you the tail. That is why a beautiful number can still disappoint, and why the mills that report variation alongside average are the ones worth trusting.

Finishing matters just as much. An untreated superfine wool can feel harsher than a well-finished medium one, and can even pill more. The number describes the fiber that arrived at the mill, not the yarn that left it.

What superfine is genuinely good for

None of this diminishes the real value of superfine wool. It only locates it accurately.

Next to skin

This is superfine's home. Comfortably below the itch threshold, it suits garments worn against bare skin — fine sweaters, shawls, base layers — where a medium wool would be felt.

Fine-gauge work

Finer fiber spins to finer yarn, which knits at finer gauges. Superfine is the fiber behind lightweight, fluid, drapey knitwear that a coarser wool cannot produce at the same weight.

Where it is not the answer

Superfine is not automatically the right choice. It is more delicate and less abrasion-resistant than fine or medium wool. For a structured coat, a hard-wearing everyday sweater, or a deeply textured cable that needs the fiber to hold its shape, a slightly coarser, more resilient wool is often the wiser pick. Finer is not better. Finer is finer.

Superfine wool on the cone

Much of the finest wool never reaches retail skeins at all. It is spun for luxury knitwear production and reaches individual makers only as surplus — mill ends from the same fine-gauge factories that supply high fashion.

On the cone, superfine wool behaves like all industrial yarn: firm to the touch, often carrying spinning oil, giving little hint of its true softness until washed. It blooms considerably. A superfine cone that feels unremarkable on arrival can transform into something that rivals luxury retail yarn once finished. Our guide to blooming explains why, and how to do it.

Because these cones are often surplus, the specification is not always complete. Where a micron figure is disclosed, it is worth more than the word "superfine" ever could be. Where it is absent, that absence is honest information — better than a confident grade nobody can verify.

How to work with superfine wool

• Trust the number, not the word. A stated micron count is verifiable; "superfine" alone is not.
• Go down a needle size. Finer fiber wants a smaller needle to keep the fabric's lightness and structure.
• Swatch and wash before deciding gauge. Superfine blooms after washing, and its true gauge appears only then.
• Consider holding strands together. Fine cone yarn is often best used doubled or tripled to reach a wearable weight — see our guide to yarn weight and Nm.
• Pair thoughtfully. Held with silk, mohair, or a fine merino, superfine adds softness and drape to a blend.

The honest answer

So — what does superfine wool really mean? It means fiber of roughly 15 to 18.5 microns, fine enough to wear against the skin, and drawn from the upper reaches of what sheep can grow. It does not mean a guaranteed softness, a single agreed number, or the best choice for every project.

The word is a useful signal and a poor specification. Read it as an invitation to ask one more question — how fine, exactly? — and the answer to that question will tell you far more than the word ever could.

Frequently asked questions