Applications Indigo (Indigofera Tinctoria L.) as Natural Dyeing in Milkfish [Chanos Chanos (Forsskal, 1775)] Skin Tanning Process

Dyeing is one of the stages in tanning process to apply base color on leather to avoid broken finishing coat. One of natural substance used in leather tanning is true indigo (Indigofera tinctoria L.). This substance has blue color and contains tannin to increase the quality of tanned Milkfish skin. The research was aimed to determine the effect of using different concentrations of true indigo application as natural substance to the quality of tanned milkfish skin. This research used completely randomized design (CRD) using three repetitions, the treatment were using the concentration of indigo 20%, 25% and 30%. The result shows that different concentrations of true indigo has significant effect (p < 0.05) to rub resistance on wet and dry coating, fastness to perspiration, tensile strength, elongation, hedonic, and micrograph photos of skin tissue. Tanned milkfish skin using 25% concentration of true indigo has the best quality based on the criteria: rub resistance on wet coating test (3.83%) and dry coating test (4.42%), fastness to perspiration (4.75%), tensile strength (1 843.53 N · cm^–2), elongation (47.61%), and skin tissue micrograph photos showing better display of collagen fibers.