Review of Conservation of Old Art Objects in Japan

Abstract

By using X-ray powder diffraction to identify the crystalline constituents of ceramics, especially porcelains, a considerable amount of information can be obtained from a very small sample. The characteristic mineral in hard-paste porcelains, stonewares and highfired earthenwares is shown to be mullite, an aluminium silicate, 3Al₂O₃. 2SiO₂, (A.S:T.M. 15–776); where there is a high calcium content aluminium silicates may occur e.g. anorthite, CaO. Al₂O₃. 2SiO₂, (A.S.T.M.10–379) and gehlenite 2CaO. Al₂O₃. SiO₂, (A.S.T.M.9–216). Among the soft-paste porcelains, whitlockite, β calcium orthophosphate, Ca₃(PO₄)₂, (A.S.T.M. 9–169), is typical of those containing bone-ash, and enstatite, magnesium meta silicate, MgO. SiO₂ (A.S.T.M.7–216) is typical of those containing soapstone. The glassy-frit porcelains generally contain a calcium silicate, wollastonite or pseudowol1astonite, CaO. SiO₂, (A.S.T.M.10–487 and 10–486). In addition, silica–either as α quartz or cristobalite–may occur in varying proportions in all these bodies.