Abstract

An environment-friendly, non-toxic, red-dyed leather was developed using four natural dyes – cochineal, lac, beet red, and monascus. The effects of the dye concentration, dyeing time, and temperature on the light fastness, rubbing fastness, colour difference, and K/S values (i.e., each dyed sample’s apparent depth value) were investigated to find the best natural dye for eco-dyeing the leather.When dyeing the leather red, the K/S value generally increased as concentrations of cochineal, monascus, lac, or beet red dyes were increased. However, the increase in the K/S value was substantially lowered when more than 5.0% o.w.l. (on the weight of leather) was used, indicating that the optimal dye concentration is 5.0% o.w.l. A dyeing time of 100 minutes was found to be optimal because the K/S value stabilized after 100 minutes. The use of cochineal 5.0% o.w.l. resulted in a 9.18 RP (plum) and the use of lac 5.0% o.w.l. resulted in a 9.52 RP. These results indicate colours that were the closest to red. Their ΔE* values, which were the levelling property indicators of the leather, were 0.56 and 0.13, respectively, showing superior characteristics compared to the other two dyes.