Maki-e is a traditional Japanese decorative technique that uses the natural lacquer Urushi and metal powders. Currently, there exist only two companies that manufacture metal powder for the purpose of Maki-e, and this research focuses on comparing the material characteristics of the gold powders with round shape manufactured by them. EDS (energy-dispersive X-ray spectroscopy) analysis, image analysis of particle shape before and after Maki-e processing, and color analysis of samples after Maki-e processing were carried out in this research. The study revealed that current gold powders with round shape had almost the same content ratio regardless of the manufacturing company and the powder diameter. In addition, spherical shape and irregular shape were observed in any gold powders, and the aggregates were observed in powder with increasing the powder diameter, while the shape of the aggregates differed with manufacturing companies. Therefore, it was indicated that the aggregates in the powder made by Asano Co., Ltd. had an influence on the particle diameter and its deviation after Maki-e processing. Moreover, the powder in Urushi resin has an influence on the Maki-e appearance because there is a color difference in polished powder, powder in Urushi resin, and Urushi resin.
Natural lacquer Urushi, which is sap collected from Rhus verniciflua, has been used as coating technique to coat ornaments, furniture, and so on for a long time. Lacquer crafts have been developed in all East Asia countries, i.e. Japan, China and Korea and so on [
A lot of lacquerwares are exported from Japan to Europe from the 16th century, so that many Maki-e lacquerwares are reported in some museums and art museums in many countries [
The materials used as Maki-e powder commonly are gold and silver powders, while Raden (mother-of-pearl) and eggshell are also used instead of metal powders. Additionally, there are several tens kinds of Maki-e powders depending on materials, shapes, and size. Especially, the shapes of metal powders, such as gold and silver, are different depending on the period or craftspeople who have made them, because these powders have been made by craftspeople for a long time [
Currently, only two Japanese companies manufacture metal powders for Maki-e in the world. However, the material properties of both companies’ metal powders are not investigated enough. Therefore, gold powder with round shape, which is called “Kin-Maru-Fun” in Japanese, is used for this research, because it has been most commonly used for cultural properties as compared with other powders. EDS analysis, image analysis of particle shape before and after Maki-e processing, and color analysis of the samples after Maki-e processing were carried out in this study to compare and examine the material characteristics of both companies’ gold powders with round shape.
Gold powders with round shape from No. 1 to No. 15 made by Asano Co., Ltd. (Series A) and Yoshii Co., Ltd. (Series Y), were used as samples. The number means the index of the particle size. The smallest powder is named No. 1, and the number increases with increasing the particle size.
Firstly, both companies’ gold powders from No. 1 to No. 15 before Maki-e processing were analyzed. After that, Maki-e samples were made with both companies’ No. 1, No. 8, and No. 15 as the representative value. Correspondence between powder number and sample names is shown in
Generally, the powders with smaller particle from No. 1 to No. 3, called “Migaki-fun”, are coated with Uwazuri Urushi, while larger particle more than No.4, called “Togi-fun”, are coated with Nashiji Urushi. Accordingly, the surface of the sample No.1 was coated with Uwazuri Urushi, and the sample No. 8 and No. 15 were coated with Nashiji Urushi. Both Uwazuri Urushi and Nashiji Urushi are refined Urushi with high transparency. The surface of the samples was polished and coated with the coating Urushi repeatedly until it became flat. Sample preparation is schematized in
Number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Series A | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | A9 | A10 | A11 | A12 | A13 | A14 | A15 |
Series Y | Y1 | Y2 | Y3 | Y4 | Y5 | Y6 | Y7 | Y8 | Y9 | Y10 | Y11 | Y12 | Y13 | Y14 | Y15 |
EDS (Energy dispersive X-ray spectrometry) analysis and SEM (Scanning electron microscope) observation of the powders before Maki-e processing was performed using a system coupled with a scanning electron microscope (JSM-6010LA, JEOL Ltd.). Image processing and analysis were performed by using IGOR Pro (6.37 A, Wave Metrics, Inc.). Average circularity and diameter of each powder before Maki-e processing were calculated. Circularity (C) was calculated with following Equation (1).
where, A is area of each particle and P is perimeter of each particle. The value of circularity is between 0 and 1, and if it approaches 1 for a perfect circle.
A digital microscope (VHX-900, KEYENCE Japan, resolution; 1600 × 1200 px) was used for surface observation of Maki-e samples at 500× magnification. Two observation images were taken. One was including reflection from the powder and the other was not including reflection because of the threshold change by white balance processing. Average diameter after Maki-e processing was calculated and color analysis of the sample surface was also performed by using IGOR Pro.
Firstly, EDS analysis was performed to identify elements in each powder. The results of EDS analysis for each powder are shown in
The SEM photomicrographs of powders from A1 to A15 are shown in
As shown in
in spherical shape and irregular shape in both companies’ powders, although the shape of the aggregates was quite different. The aggregates in Series A were consisted of larger particles than the aggregates in Series Y, while the aggregates in Series Y have rounder shape than the aggregates in Series A.
The average circularity of each powder is shown in
The average diameter of each powder is shown in
It is considered that the reason why the circularity decreased from No. 13 to No. 15 in Series A was there were some aggregates with irregular shape as shown in
The photomicrographs of No. 1, No. 8, and No. 15 after Maki-e processing are shown in
Surface of polished powder and powder in Urushi resin were observed in the sample surface as shown in
As analysis procedures, the average diameter after Maki-e processing was calculated firstly by using
Of all No. 1, No. 8, and No. 15, the average diameter after Maki-e processing of Series Y was larger than Series A. Regarding the standard deviation, only A15 was larger than Y15. Thus, only A15 was different from the results before Maki-e processing shown in
In the case of the A15, each small particle with approximately 10 µm in diameter, which was a part of the aggregates, was observed in pieces as shown in
the Y15 were polished as it is without coming to pieces. Therefore, the reason why the Y15’s average diameter was larger and the standard deviation was smaller than the A15 was because of the condition of the polished aggregates.
Secondly, the color analysis was performed to the photomicrographs of
Any part of Urushi resin showed low value as shown in
On the other hand, the average diameter of the A15 was influenced by the condition of polished aggregate, however, not only polished powder has an influence on the appearance after Maki-e processing because it was shown that powder in Urushi resin have a different color information with Urushi resin from the results of color analysis. However, the difference of RGB values in polished powder, powder in Urushi resin, and Urushi resin was not detected clearly in the case of No. 1 compared with No. 8 and No. 15, because the particle of No. 1 was small and the sample No. 1 was filled up closely with those particles as shown in
The above results revealed the characteristics of both companies’ gold powders with round shape numerically by EDS analysis, particle analysis before and after Maki-e processing, and color analysis after Maki-e processing. Only gold powder with round shape was focused on in this research, however, it is needed to analyze other Maki-e powders in the future because there are many Maki-e powders excluding gold powder with round shape. Furthermore, these research methods are expected as application for not only Maki-e powder but also evaluation method for other composite, for example, particle analysis for nanoparticle in nanocomposite.
This study clarified that current gold powders with round shape had almost the same content ratio regardless of the manufacturing company and powder number. In addition, spherical shape and irregular shape were observed in powders with any powder number, and the aggregates were observed in powder with increasing powder number; however, the shape of the aggregates in Series A and Series Y was different. The aggregates in Series A consisted of some larger particles compared with the aggregates in Series Y. Therefore, it was indicated that the aggregates in Series A had an influence on the particle diameter and its deviation after Maki-e processing. Moreover, the results of color analysis for the sample surface after Maki-e processing indicated that powder in Urushi resin had an influence on the Maki-e appearance because there was a color difference in polished powder, powder in Urushi resin, and Urushi resin.
The authors wish to thank sincerely Prof. H. Hamada of the Kyoto Institute of Technology for his contribution to this research. The authors express their gratitude to the members of Shimode Maki-e studio for their kind supply of samples for this study.
This research was financially supported by the Sasakawa Scientific Research Grant from The Japan Science Society (Grant Number 26-142).
Chieko Narita,Kazushi Yamada,Yutaro Shimode, (2015) Study on Characteristics of Gold Powder with Round Shape for Maki-e. Materials Sciences and Applications,06,841-849. doi: 10.4236/msa.2015.610086