Wool: Microns Are Not a Suit

Wool is not one texture. It is a family of animal fibres whose diameter, length, crimp, strength, contamination, colour, and uniformity vary before anyone spins a yarn. Then preparation, spinning, cloth construction, wet finishing, tailoring, and care transform those fibres again.

Fineas Jackson’s wool-suit comparison makes the central warning vivid: “100% wool” cannot predict how a suit will drape, shine, pill, crease, abrade, or recover ¹. Nor can the softest hand in a showroom. Softness is one requirement among several.

Begin at the fibre—but do not stop there

Diameter

Wool diameter is measured in micrometres, usually called microns in trade language. Fine fibres bend more readily against skin and can be spun into finer yarns; coarser fibres resist bending and can suit robust outerwear, rugs, or carpets. Woolmark identifies diameter as a major determinant of softness and end use ².

Fineas’s episodes about cashmere and exceptionally soft animal fibres use softness to unsettle a familiar hierarchy ^{3 4}. The transferable lesson is not “find the smallest micron at any cost.” It is to ask what the number predicts, whether the claim is verified, and which performance may be traded away.

Length and strength

Longer, sound fibres can be easier to align and spin into smooth, strong yarns. Short or tender fibres can increase fly, hairiness, irregularity, and pilling risk depending on the system. Mean diameter alone does not report fibre length, staple strength, or the distribution around the mean.

Crimp and scales

Natural crimp helps fibres form an airy structure. Overlapping cuticle scales contribute to felting when moisture, heat, chemistry, and agitation allow fibres to migrate and lock. These features help explain loft, insulation, fulling, shrinkage risk, and finish; they are not a promise that every wool garment behaves identically ².

Woollen and worsted are routes, not value ranks

In worsted processing, longer fibres are carded, gilled, and combed so they lie more parallel; short fibres and residual contamination are removed. The resulting yarn can be smooth, compact, and suitable for clear-faced tailoring cloth.

In woollen processing, carding creates a more mixed fibre arrangement that traps air. The yarn can be loftier, hairier, and warmer for its mass. It may suit flannel, tweed, blankets, or knitwear. Woolmark’s process guide distinguishes the routes and notes that worsted yarn commonly uses longer, more uniform fleece fibre ⁵.

Neither system is universally superior. A lofty coat and a crisp summer suit need different structures.

What Super S tells you

Suiting labels such as Super 100s or Super 150s refer to fibre-fineness categories. In the cited specification, each higher category has a lower maximum mean fibre diameter—for example, Super 100s at 18.75 μm and Super 150s at 16.25 μm ⁶.

That is real information. It is not a total quality score.

The number does not by itself specify:

• fibre length, strength, or diameter variation;
• woollen or worsted preparation;
• yarn twist, ply, evenness, or strength;
• cloth weight, weave, density, or finishing;
• resistance to seam slippage, pilling, snagging, or trouser-seat abrasion;
• canvas, lining, interlining, seam allowance, pressing, or fit;
• whether the garment can be altered or repaired.

An extremely fine, light cloth may feel exquisite and drape beautifully. It may also be less forgiving of hard daily wear than a heavier cloth using somewhat coarser, stronger fibre. “Better” must finish the sentence: better for what schedule, climate, body, and maintenance practice?

Summer wool is a system

Jackson’s summer-wool episode is useful because it breaks the equation wool = heavy winter cloth ⁷. Fibre can buffer moisture vapour, but thermal comfort also depends on yarn bulk, fabric mass, openness, colour, lining, fit, air movement, humidity, and activity. The International Wool Textile Organisation discusses wool’s moisture-vapour buffering and breathability, but it is an industry source; treat its mechanism as one input and inspect the actual cloth ⁸.

A dark, tightly woven, fully lined wool suit can be hot in sun. A light, open, unlined tropical wool can move air. Fibre identity did not reverse physics; construction changed the system.

The WOOL card

Use WOOL for a garment or swatch.

• W — What fibre evidence? Record percentage, claimed breed or origin, micron or Super S statement, certification, and unknowns.
• O — Organization of fibre and yarn: Woollen or worsted? Single or plied yarn? Smooth, hairy, tightly twisted, lofty, or irregular?
• O — Object construction: Weave or knit, mass, density, lining, seams, canvas, reinforcement, allowance, and high-wear zones.
• L — Life in use: Climate, frequency, rubbing points, cleaning, rest between wears, storage, moth protection, repair, and observed change.

Hands-on comparison

Compare two owned wool garments without pulling or abrading them destructively.

1. Photograph labels and record mass.
2. Use a magnifier to examine yarn hairiness and weave or knit geometry.
3. Hold each over the same light source to compare openness.
4. Compress an inconspicuous section for ten seconds and observe recovery.
5. Inspect cuffs, elbows, pocket edges, trouser seat, hem, and seam allowance.
6. Distinguish surface change (nap flattening, polish, pills) from structural damage (broken yarn, seam failure, thinning).

Write a job-specific conclusion: “A is softer and finer; B is heavier, more open, and shows more cloth at alteration points. A may suit occasional formal wear; B supplies stronger evidence for frequent use.”

Rule of thumb

A micron measures a fibre, not a finished garment. Follow diameter through fibre length, preparation, yarn, cloth, finish, tailoring, and use. Pay for fineness when fineness serves the job—and never ask one number to certify the whole suit.