THE WALL PAINTINGS OF GUNDS0MAGLE CHURCH, DENMARK

The whitewash on the walls of Gunds~magle church was removed after a fire in 1987, revealing in the chancel a wall painting in Byzantine style, from about 1100. The figures of two apostles are clearly visible, with traces of four more. The pigments were mixed with lime and painted on a hardened, porous lime plaster ground. The painting was probably exposed for 400 years before being covered with whitewash in the sixteenth century. The intricate technique and the alteration of some of the colours make retouching impossible without destroying the authenticity of what remains. The structure of the painting is delicate but stable, so impregnation is not necessary. The urgent problem is to prevent dirt accumulating on the painting through the turbulent motion of air rising from the heating system. A study of the microclimate shows that water vapour moves easily to and from the wall as the church is heated and ventilated, buffering the inside climate but risking salt crystallization at the wall surface. The church climate should be controlled to minimize the water vapour flux through the wall, rather than to maintain an arbitrarily chosen relative humidity.