Singapore-based dye manufacturer DyStar and Germany's RotaSpray have developed their indigo spray dyeing procedure for production on a bulk level, in a move that should help denim producers to significantly reduce their environmental impact.

The solution was first introduced at the ITMA textile trade show in Milan two years ago, and the two companies have since been working to develop it further. It has now been made available for bulk production in key denim markets such as Turkey, India and Pakistan.

The development also offers a salt-less dyeing solution for the denim industry, as well as "high flexibility" for dyeing small lot sizes, reduced water usage and effluent discharge, lower impact on yarn in the dyeing process and simplified recipe changes.

The new spray dyeing technology combines DyStar Indigo Vat 40% Solution, Sera Con C-RDA (a unique organic reducing agent) and the patented RotoDyer and the RotoCoater spraying technology.

"Although rotary atomisers have been established for several decades in the textile industry they were mainly used for re-wetting textiles with moisture," the companies say. "But recent cost pressure and a global demand for more sustainable solutions were motivators for the R&D of the industry and led to the recent technology leap."

On sheet dyeing ranges (slasher), with process and layout modifications, coatings including DyStar Indigo Coat, Cassulfon, Remazol/Levafix and Imperon dyes can be applied by spray dyeing as well. The spray application of fixing agents and oxidation chemicals can be integrated into sheet dyeing as well as rope dyeing machines.