The physical properties, color direction and color difference of stamp ink from gambier (Uncaria gambir roxb) with complexing Al2(SO4)3 compound

Abstract

The raw materials of stamp ink are usually made from synthetic materials and are toxic that can damage human health. This research uses gambier which is material from the local natural resource. The purpose of this study was to see the influence of Al2(SO4)3 on the direction and difference of color, pH, and density of the stamp ink. The study was conducted in several stages, namely the making of gambier extract, the dissolving process of raw gambier with water, drying, reducing the particle size of 100 mesh, and extracting the gambier powder with an alcohol solvent. The complexing compound Al2(SO4)3 and other supporting materials were added into the gambier extract to produce stamp ink. The stamp ink was examined the direction and difference of color, pH, and density. The optimum treatment was obtained at a concentration of 30% Al2(SO4)3 with the results of test pH 4.053; density 1.16 g/cm3; and color direction L∗ 41.579; a∗ 13.023, b∗ 21.132. The result of the stamp test on white paper showed that the color of the ink is visible, compact, unified and does not expand.