Advances in blending, weaving and dyeing wool have led to some exciting new denim fabrics, in a quietly growing segment that offers an upmarket take on winter collections. 

Adriano Goldschmied loves the idea of expanding natural fibres into denim. Inspired by the indigo hues of kilim carpets, wool blends can offer a warmer, more refined denim for winter and result in a longer life through the seasons, he says. But working with wool in denim presents no shortage of challenges, he adds. “Washing is critical, indigo dyeing is delicate and finishing demands precision – all of which once pushed many mills away from wool entirely.” These technical challenges, as well as cost, have been off-putting to mills and designers. But wool’s demand in the denim sector has been quietly increasing, particularly over the past four years, according to industry body Woolmark.

This inspired it to invest in development, working with mills such as Italy’s Berto and Pure Denim, to produce examples of new blends, textures and updated dyeing processes that could offer the sector the specifications and the performance required.

The benefits of adding some wool to garments are many, Woolmark’s R&D director, Birgit Gahlen, tells us, citing its next-to-skin comfort, thermoregulation, moisture management, odour resistance, elasticity and wrinkle recovery. Wool’s natural temperature-regulating properties make wool denim suitable for all seasons, keeping the wearer warm when it is cold, and cool when it is hot. “For instance, wool on the inside of the fabric adds an extra element of warmth and takes the initial chill out of putting on regular denim jeans,” she says. It enables designers to explore traditional patterns and subtle contemporary twists, or they can look into bold and imaginative interpretations with prints, creative dyeing methods and unique finishing touches, she adds. 

The new methods and attributes are shifting wool denim into novel dimensions. “While I’ve experimented with wool in the weft, the real breakthrough came with indigo wool in the warp, developed by Indiwool, an Indian company specialising in wool innovations,” says Mr Goldschmied. “It’s the perfect solution to showcase the fibre’s unique character.”

Technical challenges

Typically, wool needs more careful handling than some fibres and is too delicate for the slasher and rope dyeing techniques associated with denim. This is why, traditionally, indigo-dyed cotton has been used for the warp yarns combined with undyed wool weft yarns. The wool used for denim must be machine washable. Micron selection is also crucial. For shirting, the wool should be 17.5 micron or finer, with a maximum of 18.5 micron. For bottom weights, 21–22 micron is suitable for coarser weft yarns, while finer weft yarns should be limited to around 19.5 micron. “In addition to the traditionally woven twill constructions, wool denim can also incorporate weaves like herringbone, Bedford cord, seersucker, chambray, jacquard weave and dobby weave,” explains Ms Gahlen. “There are also denim-inspired wool knits and jerseys; two-thread or three-thread terry structures with a diagonal knit can be employed for unique textures and comfort.” 

To boost options, recent innovations have enabled indigo dyeing of wool, allowing the development of 100% wool “denim” (notwithstanding questions over what constitutes ‘real’ denim) – although they might not be suitable at volume level. These include fabric dyeing by Indian company Thesara, which uses a near-waterless dyeing process that applies indigo in a “reduced atmosphere” on a fabric, not a yarn. As it is a surface dyeing process, it colours a single side of the fabric at a time, with up to 80% penetration. “It is possible to achieve the authentic white core of traditional indigo yarn-dyed fabrics,” managing director Prabhakaran Chetti has previously told Inside Denim. Woolmark also tested Huilai Biotechnology’s natural indigo screen printing on 100% wool fabrics, to create a textured and faded look.

Pigment injecting

However, it is the partnership with US biotech company Colourizd that Woomark is most excited about. “After extensive testing, we realised they are on to something truly revolutionary for the wool industry,” says Ms Gahlen. “The groundbreaking process significantly reduces resource consumption, pollution and costs.”

Rather than a traditional wet colouring process that uses between 60 and 120 litres of water per kilogram of yarn, Colourizd’s QuantumColour process uses just 0.5 litres of water per kilogram and eliminates the need for bleaching and pre-treatment, and, therefore, wastewater discharge. It uses only wetting agents and a dosage of pigment and binder injected into a raw yarn fibre bundle, minimising chemical wastage and energy. Colourizd yarns range from solid to heathered to fully washed-down effects, with the final fabric appearance determined at the yarn colouration stage, eliminating the need for post-dyeing treatments.

The technology has been validated on 100% merino wool, as well as blends with cotton, Tencel and nylon, and on a range of yarn counts. “Another benefit of this cutting-edge process is that it eliminates the variability commonly associated with conventional dyeing techniques, such as shade bands,”  adds Ms Gahlen. “Furthermore, its ability to colour multiple fibre types in a single pass eliminates the complexity and cost typically associated with cross dyeing, a process that often leads to inconsistency and high resource consumption.”

Given the challenges of indigo dyeing wool yarns, “simulated wool denim” offers an alternative, says Woolmark. These fabrics are commonly woven in a twill structure using wool or wool-blend warp yarns dyed with non-indigo navy blue dyes together with an undyed wool or wool-blend weft yarn.

Novel blends and sectors

The finishing process for wool denim follows conventional denim methods but requires pH control, avoidance of strong alkaline treatments and setting at a lower temperature to help protect the wool fibres. If these are carefully controlled, the denim should be able to undergo the same processes as standard cotton denim, according to its research and after working with Tonello in Italy. However, to minimise wool fibre damage, sustainable methods such as enzyme washing, ozone treatment and laser etching are increasingly used, it adds.

Pure Denim combined cotton with recycled wool. Berto, based near Padua, has developed wool-cotton blends with more than 40% wool content in the weft, using machine washable wool yarn from Suedwolle Group, with positive feedback. The next step is to introduce an elastomer to satisfy the need for comfort requested by some customers. 

The work fed into an updated version of Woolmark’s Wool Denim Toolkit, which it launched at Denim Premiere Vision in Milan this summer, as inspiration for mills and weavers. Recent developments have also included less commonly used blends: wool-lyocell, wool-hemp and spandex-core spun wool, adding softness, texture and some stretch.

The Wool Lab sourcing guide has also been updated, containing 100 swatches of some of the best commercially available wool denim fabrics and yarns to inspire the design community. Woolmark worked with Edward Crutchley – who has designed for Dior, Fendi and Louis Vuitton – to bring the wool denim blends to life through artificial intelligence (AI). 

The nine-look collection weaves together narratives from the indigo-dyed garments of 17th-century Europe with functional layering worn by Australia’s merino wool growers. “I wanted to find ways in which the unique qualities of wool and the heritage and atmosphere created by denim could bring something new to the outerwear category of streetwear, one which has been growing significantly over the last few seasons,” he comments. “It has made me realise there is so much more potential for wool denim in outerwear than I have previously thought possible."

Mr Goldschmeid, whose latest Daily Blue collection with Pioneer Denim puts wool centre stage, sees the natural fibre gaining traction at the top end of the market. “As luxury houses deepen their presence in the denim world, the demand for truly distinctive fabrics grows,” he concludes. “Wool, with its richness and refinement, emerges as a compelling option once again. Though its cost positions it firmly in the high-end segment, its unique properties – warmth, texture and heritage – align perfectly with the narrative of modern luxury. Indigo is evolving, and as it expands into new territories, wool is quietly stepping in as its most sophisticated companion.” 

AI interprets Edward Crutchley’s vision of wool denim in streetwear.
All photos: Woolmark   

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