Reproduction of Japanese Traditional Pigment Based on Iron Oxide Powders With Yellowish Red Color
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REPRODUCTION OF JAPANESE TRADITIONAL PIGMENT BASED ON IRON OXIDE POWDERS WITH YELLOWISH RED COLOR Hiroshi Asaoka, Makoto Nakanishi, Tatsuo Fujii, Jun Takada, Yoshihiro Kusano1 and Ryu Murakami2 Department of Applied Chemistry, Okayama University, 3-1-1 Tsusima-naka, Okayama 700-8530, Japan 1 Department of Applied Art, Kurashiki University of Science and the Arts, 2640 Nishinoura, Tsurajima-cho, Kurashiki 712-8001, Japan 2 Nara National Research Institute for Cultural Properties, 2-9-1 Nijyo-cho, Nara 630-8002, Japan ABSTRACT Since the beginning of the 18th century A.D., an artificial iron oxide pigment (hematite, called “bengara” in Japanese) and having a beautiful yellowish red color, has been produced in Japan and applied to pottery, textiles and paintings. However, in 1965 the traditional “bengara” could not be produced anymore, mainly because of environmental pollution. The purpose of this study is to make clear the features of traditional “bengara” and to reproduce high quality “bengara” using modern high-purity reagents. Traditional “bengara” has been characterized as hematite containing a small amount of Al. The average size of the “bengara” particles is approximately 100 nm. The color becomes more yellowish-red with increasing Al content. A monophase of hematite prepared by heating a mixture FeSO4-7H2O and α-Al2O3 to about 680 ºC included a small amount of Al substituted in a solid solution. The particle size greatly decreased as the heat treatment temperature was decreased : 100 nm at 770 ºC but 50 nm at 650 ºC. The color of the particles becomes more vivid as the temperature is decreased, but within bounds this color is independent of the amount of Al in solid solution.
INTRODUCTION Iron oxides formed in the natural environment are one of the most primitive pigments used. It is well known that hematite (α-Fe2O3, called “bengara” in Japanese) is among various iron oxides exhibits a wide variation red colors. Since the beginning of the 18th century, Japanese merchants have manufactured synthetic “bengara” from iron minerals. It was used to color pottery, textiles and paintings with a very beautiful yellowish red color. The works by a famous Japanese potter, S. Kakiemon, which used the characteristic clear red color, had a great influence in European countries. However, traditional synthetic “bengara” is now on the brink of extinction. It could not be manufactured after 1965 because of environmental pollution. The manufacturing process produced much waste exhaust and smoke with sulfides. The modern “bengara” we can obtain commercially is high-purity hematite (99 %) that is synthesized from ferrous sulfate and sodium hydroxide. However, the color of modern “bengara” is slightly subdued in comparison with the traditional “bengara” in spite of the use of high-purity hematite. Therefore at present potters are eager to use the “bengara” with a yellowish red color similar to the traditional “bengara”.
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The purpose of this study is thus to prepare hematite with a yellowish red color similar to th
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