Color may be my favorite tool in my design toolbox. I guess it’s kind of obvious when you look at our work. I realize, a little late, that we should photograph the spaces in which the largest change is color so that you can see more directly the positive impact that color can have. Our specialty for the use of color is in architecture and interiors, but of course there is another specialty that is impacted by color, and that is textiles – fashion and furnishings.
Did you know that current techniques dyeing textiles causes pollution? Even if your wardrobe and your sofas, chairs, towels and sheets are all in shades of gray, your clothes, furnishings and bedding are dyed. Dyeing textiles requires huge quantities of water, energy and chemicals. In the primary textile locations: China, India, and Bangladesh, rivers have been reported to have unnatural hues from the chemicals released in the wastewater.
Synthetic dyes are used to color both polyester and cotton, but cotton is the more water and heat intensive process. The surface of cotton is negatively charged and doesn’t react easily with the negatively charged dye compounds. To make dyed cottons color fast – the dyed fabric or yarn is washed multiple times in hot water, creating large amounts of wastewater. 200 L of water is used to produce 1 kg. of fabric.
Apparel manufacturers are making sustainability pledges, and the $3 trillion textile industry is beginning to respond with innovative techniques. In India, under government pressure, dye factories are now recycling 90% of their water.
One of the companies innovating is Intech, located in Hong Kong. Their specialty is digital printing with pigments instead of dye, reducing water and energy usage.
A review of the textile wastewater revealed that it contains high concentrations of dyes and chemicals, including chromium, arsenic, copper and zinc. Dyes and chemicals in the waterways also block sunlight, increasing biological oxygen demand (J. Chem. Eng. Process Technol. 2014, DOI: 10-4172/215-7048, 1000182).
Another innovative dye technique is a process called “cationization” that improves the bond between cotton and the dyes. Color Zen, in North Carolina, is a start-up that has developed on pre-treatment for cotton that attaches a positively charged amino site on the cellulose charged fiber, that then naturally attracts the negatively charged dye. Color Zen treats the raw cotton fiber after the seeds are removed but before the cotton is spun into yarn. They think this pre-treatment process uses 90% less water, 75% less energy, 90% fewer auxiliary chemicals – and makes dyeing faster. It also cuts out half the dye compared with processes that call for salts in the dye bath.
Please note: All of the technical information above comes from the fascinating article in Chemical and Engineering News, July 16, 2018, page 28-33, “Greener Textile Dyeing” by Melody Bomgardner.
Ms. Bomgardner’s article also has an interesting chart that outlines the differences in dye requirements for cotton, polyester, viscose (rayon), and wool. Perhaps not surprisingly, the least environmental impact from the dyeing process is wool, and perhaps surprisingly, the most environmental impact from the process of dyeing is cotton. Let’s hope that the innovative companies showcased in this c&en article will succeed in improving a process that we didn’t realize was causing so much harm.