A new technique that dyes denim using chemicals that turn blue in sunlight could reduce the environmental impact of jeans production.

Blue denim is dyed with indigo. Indigo is a compound that was once extracted from plants, but is now usually synthesized. Harmful chemicals such as sodium dithionite are required to dissolve indigo in water so that it can be used for dyeing. These chemicals produce toxic fumes that can harm the health of textile workers and can also cause toxic pollution of wastewater.

now, Ditte Hededam Werner Researchers at the Technical University of Denmark have instead developed a new process that uses a natural precursor of indigo called indican.

“Indican is also a natural product, so it's not artificial or weird,” says Hededam-Werner. “But the good thing about this is that it's soluble, so you can basically just soak the fabric, which you can't do with indigo. So many harsh chemicals simply This made it a very attractive solution to this problem because it could be omitted.”

However, there is one important drawback. Indican is colorless, so the compound must be converted to indigo after being applied to the material. One way to do this is to leave it in the sun for a few hours.

“I don't know if consumers like it or not, but if you wear Indian-soaked jeans in the sun, they turn blue over time,” says Hededam-Werner. “You think it's a gimmick, don't you? You can do it.”

The research team has discovered two methods that can provide the faster, more reproducible results required by modern manufacturing. One method uses plant enzymes and the other uses electric light.

Using light is a simpler process that reduces the environmental impact of dyeing by 73% compared to using indigo. European Commission indicators It takes into account carbon emissions, land use, water consumption, and ozone layer depletion. Using enzymes led to even greater reductions of 92%.

Hededam-Werner said that with further research, the process could become cheaper and more efficient, but major obstacles still stand in the way, not least of which is the production of the 4 billion pairs needed. The aim is to establish a supply chain for 80,000 tons of Indican. Number of jeans manufactured each year.