Frames and supports in 15th and 16th-century Southern Netherlandish painting

41 Of vital importance in producing a panel was to master the play of the panel inserted into the constraining structure of the frame, in order to avoid the opening of the joins and prevent splitting of the wood. Verifying what rules, if any, were applied in a particular case is a difficult task that requires the contribution of dendrochronology and the experience of the panel paintings restorer. In the 15th century joinery did not achieve the same levels everywhere. During the 16th century, certain formulae, in particular those concerning the joining of the elements of the frame, spread widely and rapidly, pointing to a high degree of mobility of persons and goods. A. Positioning of the boards within the panel The careful placing of the boards within the panel reflects the attention the woodworkers paid to their work in order to achieve good results. In many cases boards that have been split rather than sawn are not of even thickness across the grain. This stems from the fact that the boards have been cut radially. The thinner narrow side is from closer to the heart of the tree, where the wood is finer-grained. The thicker narrow side comes from the outer, sapwood side of the tree, where the wood is wider- grained. For reasons of solidity, joiners preferred to leave the outward side of the board thicker and not planed back, with the resulting unevennesses picked up on the reverse of the panel. The best way to proceed with such radially cut boards, with one narrow side wider than the other, appears to have been to join at the centre of the panel two softer- wooded sides, and arrange the boards on one side like the corresponding central board, the boards to the other side like the corresponding central board, i.e. with the softer, broader side facing towards the centre of the panel and the harder, narrower side facing outward (fig. 12). We can reasonably assume that there were logical reasons to do so. The wood from the centre of the tree was placed into the grooves of the frame. The thinner side of a board is certainly less work to bevel back to fit into the groove of the frame. Another argument is that this system is the best solution for picking up retraction/swelling of the panel due to changes in relative humidity. In a panel with the boards placed in this way, retraction/expansion can take place evenly towards/away from the centre across the panel, avoiding resistance which could end CHAPTER II ASSEMBLY OF PANEL AND FRAME