Exploring ethical colour in fashion and textiles – promising innovations that are helping to reduce the impact of dyeing and finishing textiles.

Luckily some promising innovations are emerging that reduce the negative impacts of dyeing textiles, because the environment pays a high price for the colour of our clothes. A great deal of water, heat and chemicals are used in the process. The UN Environment Programme (UNEP) study on sustainability and circularity in textiles reports that the contribution of dyeing and finishing to the climate impact of the material is more than one-third of the entire textile supply chain. Many of the chemicals used remain in the water, unattached to the textile, with 20% of industrial wastewater globally attributed to the dyeing and treatment of textiles, according to The World Bank.

Since WH Perkins discovered synthetic dyes in 1856, they have taken over as the predominant method for applying colour to textiles. Compared to natural dyes, they are relatively easy to use, come in a range of vivid colours that are durable to washing and sunlight, and don’t require mordants to fix them to the fabric. However, they rely on non-renewable petrochemicals and some hazardous chemistry to do so. And their inbuilt resistance to fading, a fundamental attribute in their selection, means they won’t breakdown naturally in the environment, and so inevitably become pollution end of life.

A whole host of toxic ingredients are consumed by the industry—solvents, sulphates, heavy metals (copper, arsenic, lead, cadmium, mercury, nickel, and cobalt), acids, chlorine, formaldehyde and hydrocarbon softeners—many of which are known to be poisonous and damaging to human health and the planet. For example, benzidine-based azo dyes, which were used to dye cotton vivid orange colours and are now prohibited by regulations in many countries, are considered carcinogenic, allergenic, and harmful to the reproductive system. Similarly, disperse dyes, normally used for dyeing synthetic fabrics, are known to have allergenic properties. However, as it stands today, much of the chemistry is a closely guarded secret, and suppliers are not required to disclose the full list of ingredients.

Colour technology has become a fundamental part of clothing. As a result of the its importance in fashion and textiles, a whole industry has developed around it, estimated to be worth around USD 10 billion. As an example, the unique character of cotton denim used to make jeans, is achieved by dyeing the warp (fibres that run lengthways) and leaving the weft (widthwise yarns) white or natural. Due to the way it is woven, twill-woven denim therefore has a blue front and white back. As the denim is worn by wear and tear, the indigo-coloured yarns give way to the lighter coloured fibres beneath. This patina has become so desirable that techniques have been developed to artificially wear away the surface, such as by abrasive or chemical washing.

Naturally coloured fibre

The dyeing process consists of pretreatment and finishing process. Before colourant is added, processes such as washing, bleaching, scouring and optical brightening may be required. After dyeing the fibre and fabric is subsequently washed, rinsed and dried. Collectively, coloration and finishing are referred to as wet processes, because they typically take place in baths and tanks filled with liquid. Much of this can be avoided when inherent or natural coloured fibres are used. Hemp, linen and jute are often used in their natural colours, partly because they are tricker to dye, but also because they tend to be used in a more consciously sustainable way. Cotton is available in a range of natural colours including white, green, brown and beige. Foxfibre is a naturally coloured organic cotton from Sally Fox who was the first to grow organic cotton at scale in the US. A truly beautiful material made without chemicals. Organic Cotton Colours based in Spain, produce naturally coloured organic cotton in Turkey, Egypt and Brazil. Using regenerative farming practices, the company controls the supply chain from the field to the finished textile and garment. This ensures the absence of chemicals and guarantees a biodegradable product that is good for people and the planet. SÖKTAŞ based in Turkey produce a naturally coloured organic cotton also using regenerative farming practices. This means they pledge to restore and revitalise the soil, work with natural cycles and avoid tilling (ploughing), employing natural ground cover instead. In collaboration with the Cotton Research Institute of Türkiye, they developed Meander 71, a cotton strain that produces exceptionally strong, fine and silky fibres to rival most of the Egyptian Giza varieties.

Natural dyes

Evidence of the use of natural dyes extracted from vegetables, fruits, flowers, certain insects and fish date back to 3500 BC. Most are non-toxic and biodegradable and offer a sustainable and renewable alternative to synthetic dyes. Some bring additional benefits to the textile, associated with their properties in the life of plants, such as antibacterial, anti-fungal, UV shielding and insect repellent. For example, tannins which are present in many plants and trees are used in fabric dyeing and vegetable-based leather tanning, providing antibacterial properties and preventing decay.

However, they have a limited colour range and are not as durable to washing or sunlight. As a result, many natural dyes require a mordant, which fixes the dyestuff to the textile, giving it greater colour saturation and resistance to washing and fading in sunlight. Mordants are typically metallic salt of alum, stannous chloride, copper sulphate and ferrous sulphate. While protein fibres (animal fibres like wool and silk) are relatively easier to dye and may not require mordant at all, cellulosic fibres (plant fibres like cotton, hemp, linen and jute) do not have such good affinity with dyestuff and typically require pre-treatment to achieve good colour. Biomordants derived from plant-based materials like nutshells and bark provide an alternative to the traditional metal mordants.

Natural Dye Collection by Ficus Innovations using Circular Systems’s Agraloop Biofibre, aims to be a coloured natural fibre with the lowest environmental impact possible. They use only plant waste and extracts from pomegranate peel, olive leaf, lavender, and walnut shell, among others, along with bio-resins, plant-based oils, and clay to achieve high colour fastness. No metal mordants, aluminium salts, formaldehyde or azo dyes are used. Additionally according to the company, their natural dyeing technique saves 88% water and 55% energy, compared to synthetic dyeing.

The source of ingredients for natural dyestuff can also be a challenge, and is affected by seasonal variation and geography. A novel solution to this is to utilise agricultural and food waste products, which provide a reasonably inexpensive, reliable and low-carbon feedstock. The Food Textile project, which is tackling food waste in Japan, converts this abundant raw material into dye that is compatible with cotton fabrics. According to the project, in Japan roughly 28 million tons of food are thrown out annually. Every year, the world produces roughly 1.3 billion tons of food waste and approximately 30% of food produced is thrown away.

EarthColour dye, by Archroma in Switzerland, is derived from agricultural waste products. Colour is extracted from non-edible agricultural or herbal byproducts, such as waste leaves, nutshells and beet. The colour range is compatible with cellulosic fibres like cotton, hemp, linen and regenerated cellulose.

IndiDye natural dyes are made from renewable resources primarily based on by-products and waste. They contain no hazardous chemistry or petrochemicals, and are completely biodegradable end of life. The dyes are applied using an ultrasonic fibre dyeing process which has the advantage of reduced water consumption. According to IndiDye, conventional fibre reactive yarn dyeing uses approximately 100 litres of water to dye 1 kg of yarn. The IndiDye ultrasonic fibre dyeing process uses an average of 27 litres of water to dye 1 kg of fibre. By blending the dyed fibre with undyed fibre, such as in the formation of a mélange yarn, water and dye consumption is further reduced. IndiDye also offer clay bleaching as an alternative to chlorine-based bleaching. With this process, the fibres are bleached with naturally mineral rich clay. The process uses significantly less water than traditional chlorine-based bleaching and 90% of the water is recycled in the process. In addition, the bleached fibres and yarns are free from hypochlorous acids and other hazardous chemicals.

Waterless dyeing

Estimates for water consumption during dyeing and finishing range from 40-160 litres per kg of fabric, depending on the type and process. There is significant environmental and economic incentive to reduce or eliminate water consumption. Dyecoo in the Netherlands developed at process for dyeing textiles using recycled CO2. The gas is heated and pressurised to make it supercritical—this is the temperature at which distinct liquid and gas phases do not exist for a given material—at which point is has similar density to liquid. A specially developed disperse dye is dissolved into it and applied to fabric. It is quicker and requires much less energy than conventional wet processes.

AirDye developed by Debs in Japan use dispersed dyes that are applied to a paper carrier. With heat the dye is transferred to the surface of the textile. It is type of sublimation printing, whereby the dye converts from solid into vapour and back again, without becoming liquid. Instead of water, air is used to transfer the dye deep into the textile fibre. But while conventional sublimation printing is limited to synthetic polyester fibres, AirDye can be used on all types of synthetic fibre. The paper is recycled, there are no toxic chemicals or waste and the company claims to use 95% less water, 86% less energy and up to 84% fewer greenhouse gas (GHG) emissions compared to conventional printing and dyeing methods. Transfer printing has many other advantages, separate from the environmental benefits, such as the ability to colour the front and backside separately, and precise reproduction of multicolour print patterns in a single pass. Different to transfer printing, AirDye can be used on all types of synthetic fibre.

Digital printing is another technology that offers a waterless method for colouring textiles and compared to screen printing it uses 85% less ink and has 40% lower carbon footprint. Applying only the required amount of ink is energy efficient and minimises waste. In addition, there is no clean up necessary after digital printing, unlike screen printing and water-based dyeing processes. Kornit have developed a unique system that doesn’t require any additional pretreatment steps. Within a single process, their digital print head tracks back and forth to apply the necessary pretreatment, pigment and finishes. They are also able to apply 3D effects, by overprinting layers of white until the desired thickness is achieved. Both 2D and 3D printing techniques can be combined in a single pass in their roll-to-roll printing.

Another example is Imogo who have developed a precise technique for digital printing dye and finishing treatments onto textiles. Compared to conventional dyeing the process reduces water, chemical and energy consumption by more than 90%. It uses reactive dyes and is compatible with woven, knitted and nonwoven fabrics. The same technology can be used to bleach cellulose based fabrics as well as apply water-based finishes to textiles.

Digital printing technology may require a coating on the fabric to receive the dye, which is tailored according to the fibre type, consisting of a binder and cross-linker. Pretreatment with a coating is essential to ensure sharp reproduction of detail. The coating ensures the dye doesn’t wick and migrate over the surface of the fabric, binds it to the fibres, ensures good colour density, and wash and rub fastness. Since the emergence of digital printing, this has created a new industry in textile pretreatment, PFDP (prepared for digital print).

Pigments from textile waste

Companies have developed novel techniques for converting old garments and textiles into pigment for dyeing. Mixed textile waste is impractical to convert back into new fabrics and so typically ends up in landfill or incineration. There are of course exceptions to this rule and there is a more in-depth discussion about textile recycling in Textile recycling innovation.

Fabrics are shredded, separated by colour and pulverised into a fine powder. They are mixed with water and binders and ground up to make pigment. This solution reduces the consumption of raw materials in the production of new pigments. However, it doesn’t solve the problem of hazardous chemistry and there is also a risk that with synthetics the process of breaking down the fibres creates microplastics, which become pollution. Currently used to dye textiles and for printing, it is possible that pigments could be developed for other applications, like colouring plastics.

Officina+39 have developed a unique process to create Recycrom pigment powders from waste textiles. The fibres are transformed into an incredibly fine powder that can be used as a pigment dye for fabrics and garments made of cotton, wool, polyamide (PA), nylon or any natural fibre and blends. FiberColors dye by Archroma is made with at least 50% recycled raw materials. Mixed textiles including cellulose, nylon, and their blends, are mechanically broken down into powder used to make a range of five colours.

Colour with microbes

Microorganisms provide a renewable alternative to conventional dyeing, with many potential sustainable advantages. Huue are developing a process that use specially engineered bacteria to convert natural sugars into indigo dye. Together with Ginkgo Bioworks, they have engineered bacteria to mimic the natural processes used by plants to create colour. With their proprietary bioengineering technology they are able to produce indigo without the use of hazardous chemistry or petroleum-derived ingredients.

Colorifix bio-based textile dye is created with DNA sequencing. With this a non-pathogenic microbe is programmed to produce a specific shade of colour. The genetically modified microorganisms are fed with renewable feedstocks, such as sugars, yeasts, and plant by-products. It is transferred onto textiles and fibres using conventional dyeing equipment, but with zero harmful substances and a fraction of the water and energy necessary in conventional dyeing. Since its founding in 2016, they have bought many colours to market including indigos, mauves, pastels and beiges.