The Conservation of Flags In Sweden

Abstract

Optical and electron-beam microprobe examination of pairs of calcite crystals, mounted approximately 50 microns apart and then immersed for various times in solutions containing a barium compound and urea, showed that these crystals were cemented together by the formation of an adherent bond between the calcite substrate and the witherite filling the void space between the crystals. The bonding material was found to be composed of a series of solid solutions of barium calcium carbonate, high in calcium content at the original surface and increasing in barium content as the distance from the original crystal surface increased. The relatively rapid rate of reaction suggests that the formation of the solid solutions proceeds by a co-precipitation mechanism. The formation of the solid solutions is thought to occur most readily in pores and cracks where the calcium ions generated by the dissolution of calcite cannot readily diffuse into the bulk solution. Application of the barium hydroxide-urea treatment to the preservation of decayed calcareous stone is reviewed.