What does Ring Dyeing mean?
A characteristic unique to indigo dyeing whereby only the outer ring of the fibres in the yarn is indigo dyed, while the inner core remains white.
Heddels explains Ring Dyeing
Ring dyeing only colors the outside layer of the fibres, leaving the core white. It is usually achieved through rope dyeing rather than hank dyeing. Ring dyeing is used for jeans that are intended to fade over time as it has poor resistance to washing and abrasion.