Material Matters: Dye And Colour
It’s strange to consider that boldly coloured textiles were once a rarity, only accessible to the rich and often imported from distant, exotic places. These days we can easily get shoes and clothes in just about any colour we can imagine. Modern industrial chemists have a solid understanding of the chemical processes that go into colouring fibres, but it must have seemed like magic when the process was first discovered thousands of years ago.
The desire to brighten up our surroundings has been embedded in the human psyche from the very beginning. The earliest history of dyeing is unclear, but we can estimate that it kicked off around 6,000-9,000 years ago when nomadic lifestyles started to drop away.
Traditional, natural dyes come from some odd places. You can crush up certain insect shells to get Cochineal red, catch some cow urine for yellow and squeeze purple from molluscs or snails. You can find mineral dyes or you can turn to plants to find indigo blue in leaves, madder red in roots, brown from bark and various colours from fruit. The simplest way to dye is to put the fibre and the dyestuff into water, heat and stir. Sounds easy, but to get better results people have come up with much more complicated processes.
There are two different kinds of dye, each requiring its own unique process. The first process is known as direct dyeing, where the colour becomes fixed to the fibre without any chemical additives. One of the most well known direct dyes is indigo – the classic blue jeans colour – which comes from leave of plants in the in the Indigofera genus and can be found on almost every continent. People figured out complex processes to extract the colour around 6,000 years ago, it’s a wonder how they came up with it in so many different isolated locations.
The majority of natural dyes fall into the other category, known as mordant dyes. Mordant dyes require a kind of metal salt or tannin to be applied to the fibres in order for the dye to bond. Depending on the kind of mordant and fibre used it’s possible to get different colours from the same dyestuff. Cellulose fibres like cotton require an alkaline mordant bath, whereas protein fibres like wool need an acidic bath.
Natural dyes did, however, offer a very limited colour palette. The majority had dull, earthy tones of brown, red and yellow, while a lot of blues, purples and greens were expensive and hard to get – the textile world was quite a dull place 200 years ago. As the industry began to take off in the mid 19th century, with the help of steam power and globalisation, people were looking for new ways to dye their products. A new ‘high-tech’ industry was eventually born, primarily due to the hard work of an English chemist named William Henry Perkin.
Perkin had originally been working to synthesise an anti-malaria drug when he produced something black from coal tar. He realised that it could be dissolved in alcohol and would dye silk to a solid purple, which would become known as mauve. The young chemist patented the synthetic dye in 1856 and soon it could also be used on cotton, which had a booming industry in the UK. Industrial chemists began to unlock the secrets of different colours, one by one killing off natural dye trades, as they figured out how to synthetically replicate natural pigments.
From the work done on synthetic indigo in the late 19th century, a new class of vat dyes were discovered for cellulose fibres and by the beginning of the 20th century there were a wide range of colours available. Once chemists had pigments locked down they could create all kinds of colours. By the 1920s there was a need for new kinds of dye to colour newly discovered synthetic fibres like rayon, as they became a cheap alternative for natural fibres like silk. This lead to the discovery of disperse dyes in 1923, which have the smallest molecules of any dye. Beyond dyeing, the technology has even come far enough with synthetic materials to embed pigments directly into their makeup.
Nowadays it’s highly unlikely that you own any naturally dyed sneakers, or anything for that matter – unless you were one of the lucky few who got the recent Nike Flyknit Racer, which was hand-dyed using natural indigo by Japan’s Buaisou – and pretty much every shoe you own will have dyed elements on it. The synthetic dye industry creates around 500,000 tonnes of dye each year, which would help to explain why we live in such a vibrant world. When you consider the amount of chemicals that are flushed away during the dying process it is important to think about the effect that all this colour can have. Some areas in China and India have toxic levels of pollution in local waterways due to poor practices and a lack of industry regulation. Unfortunately it’s hard to trace where textiles have been dyed, as it goes back so many step in the process, but it’s important to remember that it plays a big part in the environmental impact your purchases can have.,
Both Nike and adidas have incorporated environmentally friendly waterless dying methods into their production over the past few years, but at this point it has a much higher cost, as well as various other limitations, so is yet to completely takeover. Waterless technology includes processes such as transferring dye from paper onto polyester, in a kind of printing process, or pressurising powdered dye into the fabric with CO2. As far as cotton goes, there are certain pre-treatments that can be applied that reduce water use by 90 percent and chemical use by 95 percent.
Colour can make or break a shoe, but it’s not often you hear sneakerheads talk about where that all came from. Let’s be thankful that there were so many curious minds throughout history that went the extra step to brighten up the world we live in.
Material Matters is our weekly tech section, where we take a peek behind the mesh curtain and break down the building blocks of the industry. Recently, we’ve looked at Leather, Ripstop Fabric and EVA Foam.