Glitter comes in many colours, but these scientists are making a green alternative

Glitter is eye-catching but it's also a pollutant, so researchers have turned to plants to solve the problem.

A team of scientists at the University of Cambridge has created a sustainable glitter that does not contain any plastic, pigments or reflective metals. It is made from cellulose plant fibre, and it is just as sparkly and colourful as the glitter found in make-up and children's crafts.

As Silvia Vignolini, a professor of chemistry at the University of Cambridge told Quirks & Quarks host Bob McDonald, glitter is often made by layering plastic and other components. 

"Generally you have a small metallic layer underneath. Then on top of the metallic layer, you have a layer of plastic with other types of pigments that are embedded inside," she said. "So even if you could collect it after use, it would be a problem to recycle." 

Vignolini points out that glitter has been found to be a component of ocean microplastic, and other research has suggested it can have impacts on freshwater ecosystems.

All that glitters is green

Vignolini and her colleagues have been trying to develop new optical materials from sustainable resources, and recently they had success making glitter out of cellulose plant fibre. They published their results in the journal Nature Materials.

"In nature, you have many different plants that actually use cellulose as pigmentation to make colour," Vignolini said. "By looking at the architecture of the cellulose in plants, we started to think that maybe we can create materials that have a similar type of structure and a similar type of optical response.  We then came to figure out you can also make glitter." 

The team first tested their technique on wood pulp, but according to Vignolini their work suggests any plant can be used, including so-called waste materials like mango peel, banana peel and the skins of coffee beans. All of these materials contain cellulose, which is easy to extract, and can be rolled into sheets of cellulose film in a process similar to making paper. The film is then ground into small particles of glitter.

The colour comes from the way light can play on tiny cellulose crystals in the cellulose film, a phenomenon called structural colouration. These nanoparticles of cellulose can be manipulated chemically to form helicoidal structures — shaped like a spiral staircase — that give off colour by reflecting and refracting visible light waves, depending on the size of the steps and how they are arranged.

Vignolin compares it to the way colours appear when light shines on soap bubbles. In this case, cellulose, like water, is transparent, and the light reflecting or scattering on the helicoidal structures will cause different colours to appear.

Why glitter glitters

The same light-bending phenomenon produces some of nature's brightest colours, such as those found in butterfly wings or iridescent bird feathers. 

"The colour depends on the angle of observation," Vignolini said. "Depending on the direction you are looking at it or from which direction it is illuminated, the colour disappears or appears in different angles. That's what gives you this metallic glittering effect."

In Europe, the cosmetics industry uses an estimated 5,500 tonnes of microplastics every year. Vignolini focused on glitter in her research to show that something many people use on a daily basis creates an environmental problem that can be solved. But she thinks the potential of the research goes well beyond glitter. 

"The aim would be really to try to replace pigment from a wide variety of applications, from inks in printers, to cosmetics, to food coloration to even colour used in paint," she said. "Ideally, we would like to really make an impact in the direction of making colour in a more sustainable way with more sustainable materials."

Written and produced by Mark Crawley.