Microstructure and formation conditions of the reddish hi-iro marking on traditional Japanese ceramics

Yoshihiro Kusano, Teruaki Danno, Keiko Tokunaga, Nobuaki Kamochi, Hideki Hashimoto, Makoto Nakanishi, Tatsuo Fujii, Minoru Fukuhara, Jun Takada

Research output: Contribution to journalArticlepeer-review


The microstructure and conditions for the formation of the reddish color referred to as hi-iro on Japanese ceramics were investigated through model experiments. The hi-iro marking was found to be formed by the reaction between clay and alkali ions supplied from the glaze. When a mixture of porcelain clay and 20 wt%KCl was heated in air at 1250°C and then cooled slowly to 800°C, hi-iro clearly appeared on the sample surface. In hi-iro, corundum [α-(Al,Fe)2O3], hematite (α-Fe2O3) and a liquid phase are formed. Upon heating until 1250°C, corundum is firstly precipitated as hexagonal plate-like crystals. During the cooling process, hematite precipitates on the edges of the corundum crystals to form specific composite particles. When rapidly cooled from 1250°C to room temperature, a brownish red color appeared on the sample surface, which was found to be caused by the formation of approximately 50μm Al-substituted hematite (Fe1.9Al0.1O3) particles. The relationship between the microstructure of the phases formed and the color is discussed.

Original languageEnglish
Pages (from-to)942-946
Number of pages5
JournalJournal of the Ceramic Society of Japan
Issue number1396
Publication statusPublished - Dec 2011


  • Corundum
  • Hematite
  • Hi-iro
  • Microstructure
  • Reddish color
  • Traditional ceramics

ASJC Scopus subject areas

  • Ceramics and Composites
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry


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