People all over the world love blue jeans, but the process currently used to dye jeans with indigo can be harmful to the environment. Working with an Ithaca College student and colleagues from Virginia Commonwealth University and the University of Leeds, chemistry professor Mike Haaf recently developed a new, more environmentally friendly way to dye fabric with indigo. They published a paper on their research in the journal Coloration Technology. In an interview with IC News, Haaf explained how this new process works.
IC NEWS: How is indigo traditionally used to dye fabric?
HAAF: Indigo is a special dye [both] because of its beautiful blue color, but also because unlike other dyes, it doesn’t dissolve in water at all. It’s completely insoluble. To get the blue into fibers for jeans and things like that, indigo first has to first be converted to something called leucoindigo, which is an ugly, yellow, apple-juice kind of color that dissolves in water. Then they put the fiber in and let the dye soak into the fiber. When they take the fiber out of that vat, oxygen from the air re-oxidizes the leucoindigo back into indigo. It’s called the vat-dyeing process.
IC NEWS: How is your new process different from vat dyeing?
HAAF: Our process eliminates the need to turn indigo into leucoindigo. It basically allows you to make indigo and then capture it in fibers as its forming, so you don’t have to do that extra conversion.
Normal organic synthesis is done in batch process, where you mix stuff in a flask, stir it, and then get a product and isolate it. This method uses something called a flow reactor, where you’re actually synthesizing the material in small, microfluidic channels, using reagents that flow through those channels. So it’s not in a big batch. The reaction is happening on a very small scale, but continuously.
For our process we took the components that you’d normally mix in a flask and separated them into different channels, and then had them mix. The indigo is formed in-flow, and so if you are careful enough with your conditions you can take a fiber and capture the indigo microseconds before it finishes forming, so that it soaks into the fiber and turns blue without having to do that vat-dyeing step.
You can also aerosolize it. You can run that through an aerosol can and make a sprayable form of the material.