57 The Holy Cross retable A second matte gilding technique was used in the “Arma Christi” paintings. The background of these depictions had been stippled with tiny gold dots (4-6mm) in a mordant technique. Although lost except for some very small remaining traces, the decoration can be described as being made by the application of a viscous binding medium, which was subsequently gilded with gold leaf after reaching the desired tackiness. Excess of gold leaf was brushed away after drying of the mordant. Due to deterioration and (possibly hygroscopic) surface tension of the medium, all dots have disappeared, leaving a shallow white lacuna of their former position in the preparation layer (Fig. 78, 79). Following the application of the gold leaf and the burnishing process, the matte monochrome deep blue glue-paint containing coarse smalt particles was applied to contrast the gold and to define the contours of the gilded carving (Fig. 84, 85). The smalt on the frieze, the pilasters, and the columns is particularly colourful due to the coarse grain. The pigment particles and the grainy surface are clearly visible to the naked eye. All other polychrome areas are painted very thin in a layering system, based on a first layer of the general background colour, subsequently followed by the details of either ornaments, contours or the detailed pattern of the paintings like the “Arma Christi”. The medium is very water sensitive, most likely it is based on a glue distemper and applied in very thin washes. The watery consistency is clearly visible in irregularities and traces of brushwork, showing more or less dense areas of applied paint. The whitish preparation layer is used as a white background and is left visible around the main formal elements (Fig. 86, 88). Fig. 84: Cross-section through blue area; coarse smalt particles on multilayered preparation
RkJQdWJsaXNoZXIy MTI5NTQ=