An energy-saving method of organic dyeing of agates

Brazil is one of the leading suppliers of colored agates, mostly of its extraction and processing carried out by artisanal miners. Dyeing is the principal method used for color alteration, and the long heating times account for most of the energy consumption. In this context, this study aimed to evaluate the implementation of a cold dyeing procedure, dispensing any need for dye solution heating, for the cases of organic dyeing with Rhodamine B and Crystal Violet. The results obtained indicated that using cold dyeing allowed obtaining coloring levels similar to those produced commercially. Also, for some cases, satisfactory color alteration could be achieved using dye concentrations lower than that conventionally used. The proposed cold dyeing process arises as a sustainable option for saving energy, reduce greenhouse gas emissions, decrease solvent losses, and enhance the income of artisanal and small-scale producers.