Flax Fibre

Flax is grown either for fibre or for seed, and the two are distinct crop types with distinct commodities at the end. Fibre flax is bred and grown to produce a tall, slender, unbranched stem — long stems mean long fibre bundles — and it is sown densely to suppress branching. Linseed, grown for the oilseed, is shorter and branched, because the object is to set seed rather than to build stem.

A grower chooses between these ends rather than getting both. A fibre crop harvested for seed sacrifices the stem quality that makes the fibre worth having; a linseed crop’s straw yields fibre that is short, coarse, and hard to process. Some fibre from linseed straw does find technical uses, but it is not a substitute for the fibre-type crop, and the two are not the same commodity.

Fibre flax is pulled rather than cut. The fibre bundles run the full length of the stem and continue toward the root, so cutting at stubble height would throw away usable length and leave an uneven butt end. Pulling machines lift whole plants and lay them in a swath, preserving the full stem.

Retting is the controlled step that everything else depends on. The fibre bundles are cemented to the woody core and to each other by pectins, and retting uses microbial and enzymatic action to break those pectins down so the fibre can be separated. In dew retting, the pulled swath is left lying in the field and the work is done by field micro-organisms under weather the grower does not control; water retting, historically important, submerges the straw instead. Judgement here is everything: under-retted straw will not give up its fibre and scutches badly, while over-retting attacks the fibre itself, weakening and darkening it. Retting cannot be undone in either direction.

Retted straw is then baled and taken to a scutching mill, where it is broken and beaten to shatter the woody core and shake it out. This yields long, aligned line flax; the shorter, tangled fibre separated alongside it is tow, a genuine second stream with its own uses; and the shattered woody core falls out as shive. Hackling — combing the line flax — refines it further and produces more tow.

Flax fibre is bought on length, fineness, strength, colour, and cleanliness, and — unusually among fibre commodities — much of its assessment remains a matter of expert handling and appearance rather than instrument readings alone. Colour is read as a record of retting: a well-retted, evenly weathered fibre has a characteristic even tone, while patchiness signals a swath that retted unevenly.

• Under-retted fibre that resists separation and carries adhering core
• Over-retted fibre, weak and dark
• Uneven retting across the swath
• Excess shive and dust left after scutching
• Short, tangled, or broken fibre reducing the line fraction
• Weathering damage from a swath caught by poor weather

Grading is by trade convention and buyer specification rather than by a single international standard, and the terms used vary between the European growing regions that dominate fibre-flax supply. This entry reproduces no grade tables.

Line flax is spun into linen yarn for apparel and household textiles, the market that has carried the fibre for millennia. Tow goes to coarser yarns, twines, and — increasingly — to nonwoven and composite applications, where flax is used as a reinforcement fibre rather than a textile one. Technical and composite demand has made the short-fibre stream more valuable than it once was.

Shive, the woody core broken out at scutching, leaves the mill in large volume and is put to use as animal bedding, particleboard furnish, and fuel. It is a low-value residual relative to the fibre and is modelled here as a by-product of flax fibre production.