How to Wash Tencel (Lyocell)

The Chemistry

Tencel is the brand name used by Lenzing AG (Austria) for its Lyocell fibre. Lyocell is a regenerated cellulose fibre — like viscose and modal — but manufactured via a fundamentally different process that produces a fibre with a distinct internal structure and a unique failure mode that neither cotton, viscose, nor modal share. Standard viscose and modal both use variants of the xanthate process, where cellulose is chemically converted to cellulose xanthate (a soluble derivative), dissolved, extruded, and then regenerated as cellulose fibre in an acid bath. This chemical transformation degrades some cellulose chains in the process. Lyocell (Tencel) uses the NMMO process — N-methylmorpholine N-oxide, an organic solvent — which dissolves cellulose directly without any chemical conversion. The cellulose molecules remain intact throughout dissolution and extrusion. The result is cellulose filaments with a higher average degree of polymerisation (longer polymer chains) than either viscose or modal. These longer chains, combined with the high-draw extrusion process similar to modal, produce a fibre with very high crystalline orientation. Tencel is approximately 30% stronger than cotton when dry, and remains strong when wet — unlike standard viscose, which loses 40–50% of its strength when wet. In fact, Tencel is slightly stronger wet than dry, a property it shares with linen and hemp but not with cotton (which is approximately 15% stronger when wet) or standard viscose (strongly negative). The NMMO solvent is 99.5% recovered and recycled in closed-loop production. The remaining 0.5% is treated and discharged safely. This makes Tencel the most environmentally closed-loop of all regenerated cellulose fibres — substantially better than standard viscose and somewhat better than modal. The cellulose source is typically wood pulp from certified sustainably managed forests (primarily eucalyptus or beech). The unique failure mode of Tencel that distinguishes it from all other cellulose fibres is fibrillation. Tencel fibres have a characteristic microfibrillar structure: the outer surface of each fibre is composed of microscale cellulose fibrils that are bonded to the inner fibre core but project slightly from the surface. Under mechanical stress when the fibre is wet — particularly friction between fibres in a washing machine or agitation in water — these surface microfibrils can split and peel away from the fibre core, creating a diffuse, fuzzy bloom on the fabric surface. Fibrillation is not pilling (where loose fibres ball up on the surface). Fibrillation is a structural event at the fibre surface itself. The effect is particularly visible on dark-coloured Tencel garments, where the fine white microfibril fuzz creates a grey or white surface haze. On light colours it is less visible but still present. Once fibrils have split from the fibre surface, they cannot be pushed back — the damage is structural and permanent at the microscale. Lenzing has invested heavily in manufacturing modifications to reduce fibrillation tendency in modern Tencel. Commercial garment production uses cellulase enzyme treatment during finishing (cellulase digests the loose surface fibrils, removing them before they cause visible damage) and sometimes crosslinking treatments to bond the surface fibrils more firmly to the fibre core. The result is that modern TENCEL brand fabric from reputable garment manufacturers is significantly more fibrillation-resistant than first-generation Lyocell (1990s–early 2000s) and generic Lyocell from manufacturers who skip the finishing treatments. However, the potential for fibrillation is never zero, and aggressive mechanical washing will eventually cause it. The practical implication for home laundering: gentle cycle, lower agitation, mesh bag, cold to 30°C washing temperature, and shorter spin cycles reduce the mechanical friction that causes fibrillation during washing. Tencel has excellent moisture management properties. The microfibrillar surface structure and high crystallinity create a large, consistent surface area that draws moisture away from skin rapidly. Tencel is typically more breathable and temperature-regulating than cotton of equivalent weight. These properties make it popular for bedding, underwear, and next-to-skin garments.