Technology of Free Chrome Tanning Process: Optimal Level of Formaldehyde as Tanning Agent for Mondol Stingray (Himantura gerrardi)

Chrome (VI) has a high level of toxicity. Formaldehyde is potential to be developed as a substitute of chrome tanning agent. The aims of this study are to explain the amount of formaldehyde bound, shrinkage temperature, tensile strength, and tear strength on Mondol stingray (Himantura gerrardi) leather. Pickled mondol stingray has been used as raw material. The study was divided into 4 treatments, that is P.I (formaldehyde 2%), P.II (formaldehyde 4%), P.III (formaldehyde 6%), and P.IV (formaldehyde 8%). The method used is drum tanning. Shrinkage temperatures, tensile strength and tear strength of P.I and P.II are significantly different from P.III and P.IV, but P.I is not significantly different from P.II, whereas P.III is not significantly different from P.IV. P.III is shown to improve the quality of leather stingray more than P.I and P.II, and has fulfilled the requirements of leather stingray according to SNI. 06-6121-1999. It can be concluded that the optimal level of formaldehyde tanning agent that can be used as a chrome tanning agent substitute in tanning Mondol stingray skin is formaldehyde 8% (P.III).