Abstract
Hematoxylin is extracted from heartwood of the Logwood, commonly used as a natural dye, and oxidized to its quinoid product hematein. Hence Logwood extracts include both of hematoxylin and hematein, and are usually used in staining as lakes of the oxidation product hematein with metal ions. For example, hematein-aluminum is the most widely used in stain biological tissue. However, the behavior of hematoxylin in solutions has not been elucidated yet. In this paper, the oxidation of hematoxylin available as a reagent at various conditions in solutions and its adsorption by silk were investigated. The UV/VIS spectra of hematoxylin in aqueous solutions and on silk after dyeing were recorded at various pH values. The surface colors on silk fabrics were shown as K/S values, which were calculated by the Kubelka-Munk formula. As a result, the color of the dyed silk was affected not only by hematoxylin existing in the solutions, but also by the conditions such as pH and temperature. The optimum condition was determined as pH8 (20°C), pH7 (40°C), and pH6 (60°C) at dyeing for 120min.
