Denim Know-How: Responsible denim dyeing solutions

An essential stage in the production process, denim dyeing is one of the areas where the environmental impact can be reduced the most. Efforts are focused on a number of aspects: use of natural and organic dyes, reducing the use of chemical products, energy and water.

The organic denim dyeing alternative

As an alternative to conventional colorants, dyes from nature are a first choice. These so-called ecological dyes are produced from plant-based or mineral organic elements.

Indigo remains the preferred colorant in the denim industry. To replace the synthetic version, use of the plant Indigofera Tintoria offers an interesting alternative, notably when it comes from a renewable source. In order to avoid excessive extraction that could be harmful to biodiversity, other sources of colorants are being developed with very specific aesthetic results.

The most commonly used plant versions come from fungus, herbs, flowers or wood extracts, while the mineral colorants use pigments from rocks or soils, such as clay. As it requires no chemical products, this technique is totally harmless. From an environmental point of view, it is biodegradable and can boast of being hypoallergenic for humans. An ancestral technique, it has benefited from the technological developments made by exhibitors. Colorants now fix better than before on denim and produce very specific color finishes.  Completely in line with the natural aesthetic that has been in demand in recent seasons, they are now producing randomized, faded or evanescent effects.

Eco-sustainable denim dyes only use organic and compostable raw materials. Plants – flowers, berries, roots – are dried then infused without chemical additives, meaning that any waste produced by these dyes is totally biodegradable and free of micro-plastics.

New generation colorants

Research and innovation by dyers are focused on the bio-production of colorants with enhanced performances. Produced from food and agricultural waste, these natural polymers are often the fruit of recipes concocted in-house by dyers and can even be patented. 

Examples include waste prawn shells, or plants such as marc from grapes, mushrooms and eucalyptus fibers initially used to produce cellulose fibers such as Tencel. Used during the dyeing process, at the bonding stage in particular, these biopolymers considerably reduce the use of water, chemical products and energy, in comparison to conventional methods. Entirely biodegradable, these new general colorants also facilitate product recycling when it reaches its end of life.

This method makes it possible to achieve a wider palette of denim colors, including vintage appearances.

Denim dyeing: less is more

Indigo, whose intense blue pigment powder has very high coloring power, is difficult to dissolve in water. Therefore, it often involves a chemical process and a large volume of water for it to be used as a dye. These are areas in which exhibitors intend to act in order to improve sustainability performances. The result is new innovations arriving on the market and appealing to our exhibitors, such as an indigo dye with a foamy texture that makes the product easy to apply. 

The emulsion is spread over the fabric, which immediately takes on an intense indigo color. This technique does not require colorants or chemical solvents, such as aniline, and also consumes virtually no water or energy, yet produces results equivalent to a conventional dye!

Another example is the transformation of indigo colorants from soluble to liquid. This liquid format becomes directly usable for dyeing, improves the dyeing of the threads and means there is no need for the chemical agents typically used in classic dyes, such as sodium hydrosulphite or caustic soda. These substances are particularly toxic for the environment if they are poorly managed.

These different techniques generally make it easier to achieve accreditations that prove the absence of toxic substances, including Standard 100 from Oeko Tex® or compliance with the European Reach regulations on chemical products.

Another process involves having the color pigment penetrate less deeply into the thread which consequently reduces water and energy consumption.

Azo dyes

Azo dyeing allows the indigo to penetrate very deeply into the thread. During the dyeing process, the threads to be dyed is moved through a chamber filled with nitrogen, and this is accompanied by a chemical oxidization reaction. The pigment reacts to the oxygen and the dyeing process is intensified.

This technique reduces the number of conventional baths required from 7 to 2, and also results in a reduction of chemical products as the process does not require hydrosulphite or fixing agents and uses considerably less water. By penetrating far into the thread, the resulting dyes are deep and not limited to blue, as grey and black are also possible. They maintain their color for a long time and do not run.

For a number of seasons now, Denim Première Vision has been advocating for eco-responsibility and through a selection of products has been showcasing the efforts of its exhibitors to offer more environmentally-friendly denims. Let’s not forget that denim was one of the first textile sectors to have embarked on a cleaner approach and solutions are multiplying along the entire production chain to achieve a virtuous circle, with technical and technological solutions that enable the production of an attractive selection of eco-designed items.

In our articles on responsible denim, read about the sustainable innovations from Première Vision exhibitors to guide your sourcing and build your future collections.

Read our article on eco-responsible finishes for denim and accessories, to continue your denim sourcing and achieve a global responsible approach.

And continue your denim sourcing online at the Première Vision Marketplace and at our twice-yearly Denim PV shows in October and May.

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