A Masterly Hand / Scientia Artis 9

of the specific characteristics of the wood used, with questions regarding wood selection. Then the different statues made from a single tree are discussed, and the chronological data obtained by the tree rings is further detailed, as well as the geographic provenance(s) of the wood. All information obtained from the tree rings is considered in the production context of the workshops grouped under the name ‘Master of Elsloo’. Methodology Applied to the Elsloo Gr oup 4 Dendrochronological analyses of works of art are subject to different constraints than analyses of roof beams or archaeological material, which do not have the same artistic value. Examination of sculptures needs to be done in a non- destructive way, thus without destructive sampling. Therefore, the tree rings must be visible directly on the object; on this kind of sculpture this is on the base. In the Elsloo group the trees used for certain sculptures, such as the apostles of Neeroeteren and Ellikom, have very wide rings, typical of a rapid growth rate. This means that, if the wood is in fairly good condition, the rings are readily distinguishable and thus measurable without prior preparation or after simple surface cleaning with a brush (figs. 8.4a-b). When the surface is more irregular or when the rings are narrower (Bishop Saint in Siersdorf, Virgin of the Calvary in Ellikom), minor preparation with a blade is done along one or several rays with the largest number of rings (figs. 8.4c-d). In the case of significant degradation, several series of measurements are made for each piece. In total, ninety-four tree-ring sequences were recorded for the fifty-two sculp- tures included in the project. The ring series are recorded using macro-photographs calibrated by a milli- metric scale (figs. 8.5a-c). A specific computer programme allows the ring widths to be measured directly on the computer screen (fig. 8 .5d). 5 A major difficulty in the dendrochronological examination of the Elsloo sculptures is the limited number of rings on many of them. This is due to the fact that several works were sculpted from fairly young trees (less than seventy years old) and that large sculptures have been hollowed to avoid cracking and distortion of the wood during drying, reducing the analysable length of the ring series (Christ on the Cold Stone in Neeroeteren, St Anne with the Virgin and Child in Maaseik). Yet to achieve a reliable result, a sufficient number of tree rings must be pres ent. 6 A series of around thirty years is statistically too short for a reliable date: the risk of obtaining several probable chronological positions means that no date can be regarded as absolutely certain. Sequences of around fifty rings may lead to a definitive result, as long as a significant number of contem- poraneous pieces of wood are available for analysis. Typically, to provide an unequivocal result, a minimum of seventy to eighty rings is needed. The higher the number of rings, the more reliable the date. 7 Th is requirement is probably partly responsible for the scarcity of dendrochronological studies on sculptures in the round. Indeed, if made of oak, these are often carved from rapid-growth trees: they therefore have few ri ngs. 8 In the Elsloo group, the ring series of the fifty analysed sculptures contain between nineteen and one hundred and thirty-one rings (se e table in appendix) . 9 Fig. 8.4 Different types of growth rhythm of oak a-b Apostle, Neeroeteren, St Lambert’s Church, underside showing the rapid growth of the tree (wide rings) c-d Apostle Matthew (?), Utrecht, Museum Catharijneconvent, inv. ABM bh289, underside showing the slow growth of the tree (narrow rings) and the presence of a number of sapwood rings (lighter part) 8.4 a 8.4 b 8.4 c 8.4 d