A researcher from Iowa State University (ISU) has discovered a natural and environmentally friendly way to add color to clothing and other textiles, by using spent coffee grounds.

ISU graduate student Changhyun Nam first began experimenting with the grounds leftover from his daily coffee, before eventually gathering grounds from local coffee shops. Nam dried the spent coffee grounds for three days before boiling them in purified water to draw out dyes.

Source: Iowa State University

Nam went on to test those dyes on materials such as linen, silk, rayon, cotton and polyester, using an assortment of mordants, which is a substance commonly used to help dye bond to fabric. This resulted in an even greater variety of shades of brown.

While using coffee grounds as a sustainable dye alternative serves a variety of functions including diverting coffee ground waste from landfills, there is at least one significant limitation to the approach, according to researchers.

"One disadvantage of natural dyeing is that it's hard to measure the quantity needed to get the exact same color," explained assistant professor Chunhui Xiang, who oversaw the study.

"For each batch of dye, there may be a difference in the type of beans or maybe the coffee was brewed twice. Creating an exact match is a challenge, especially for manufacturers."

The team believes that additional work is necessary for it be an appropriate option for mass production. The coffee-based dye is a potential alternative to the two million tons of chemicals and synthetic dyes used annually in the textile industry.

Currently, Nam is experimenting with coffee dye and the cellulosic fiber from kombucha tea to create shoes.

The article, titled "Natural Dyeing Application of Used Coffee Grounds as a Potential Resource," is published in the International Journal of Fashion Design, Technology and Education.