Our River Denim is hank dyed in natural indigo, just like our Hank 2 and Hank 8 fabrics ...though the process are quite different.
"Hank dyeing" essentially means the yarns are dipped and dyed manually by hand, and it's quite different to "rope dying" which is how most indigo yarns are coloured. Hank dying takes a lot of care, attention to detail, and human involvement - but it inevitably produces more irregularities (which we love).
Our River Denim is made from organic long staple cotton, grown and hand spun locally. Most operations in the area who work in the process are family run cottage industries, and we were lucky enough to meet a family of dyers who have been trusted with the River Denim yarns.
After the yarn is picked, spun, and delivered to the family, they tie the ropes together to keep them neat and even.
They're then soaked for several hours (preferably overnight) before being pulled out and drained. This process is important; too much water would dilute the indigo bath, but dry cotton won't accept the dye in the right way.
The family thought it was hilarious that we found their rubber gloves so beautiful -- but after years of indigo dying even stubborn rubber has yielded to the might of indigo.
The ropes are then attached to a long pole and dipped into an enormous bath of natural indigo (this is the best part). They're slowly rotated so every inch of them sits in the indigo bath, then rises out to oxidise and set.
As you can see, indigo dye begins as a bright green colour, but starts to turn blue the moment it touches air.
They're left to sit in the bath for some time, before being taken out and drained in a large empty pot. Once they're fully oxidised they're taken back to the dye bath for another dip to even up the tone and get a richer, deeper colour.
This method of natural indigo dying uses chemicals (unlike the Hank 2 and Hank 8) which means the yarns only need to be dipped twice to reach a deep blue shade.
Finally the yarn is given one last rinse in clean water and hung to dry. They're dried inside as the sunlight would give uneven results, and could even bleach parts of the yarn. They're then packaged up and sent on to be picked up by the weavers!