Flax plants grown for fiber require well-weeded well-drained soil, and a cool, humid environment. The plant is harvested when the stems begin to turn brown. Any delay in harvesting results in deterioration of the fiber, causing it to lose its luster and softness. The plants are often harvested by hand, uprooting the plant to preserve the length of the fiber. Flax is also harvested mechanically, but fiber length is sacrificed to some degree. Good fiber is 12-20 in (20-30 cm) long. The seed pods (bolls) are separated from the uprooted plants, either mechanically or by hand, a process called rippling.
The uprooted plants, now called straw, are then retted. This is a process by which bacteria and fungi are allowed to rot the semi-woody stalk tissues, and break down the gummy substance (pectin) that binds the fibers together. If the straw is not retted enough, removal of the semi-woody stalk is difficult, but if the straw is over-retted, the fiber is weakened. In pool or dam retting, the straw is placed in a tank of warm water, while in dew retting it is spread out in a field, allowing the straw to become dampened by dew or rain. Stream retting is a method where the flax bundles are put into flowing streams, and this produces the best linen fiber. Straw can also be retted chemically. The various retting processes are used to create various shades and strengths of fiber.
After retting, the straw is dried and put through a machine called a flax brake, which crushes the stems into small, broken pieces called shives. The shives are removed from the fiber by a process called scutching, done either mechanically or by hand. The fibers are then straightened out by hackling or combings, sorted according to length, and baled. The long fibers, called line fiber, are used to make fine fabrics, threads used for bookbinding and shoe making, and twine. The short, damaged or tangled fibers, called tow, are used for products such as rope, and rougher linen yarns.
The finest, strongest linen is made from flax immersed in hot water, and spun while wet; dry spinning produces a rougher, uneven yarn. Linen yarn is very strong, but inflexible. Flax fiber is basically pure cellulose, and is not very porous, making it difficult to dye unless the cloth is bleached first. The manufacturing of linen is very labor intensive and its price reflects this fact. France and Belgium have the reputation of producing the highest quality linens.