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

ASSEMBLY OF PANEL AND FRAME 45 8. “Il faut aussi avoir soin que les joints soient bien droits sur la largeur des planches, et qu’ils portent bien des deux côtés […] parce que les joints ainsi bien approchés, empêchent l’air d’y pénétrer, et par conséquent de faire tourmenter les panneaux. Après avoir fait les joints avec toutes les précautions […] on les colle […]; puis on chauffe les joints afin que la chaleur faisant ouvrir les pores du bois, le dispose mieux à prendre la colle, laquelle les trouvant ouverts s’y agraffe et retient les joints […]. Quand la colle est chaude on l’étend sur les joints avec un pinceau ou brosse faite de poils de sanglier. Ensuite on approche les joints et on les frappe avec le maillet.” Quoted from Roubo 1977, 80-81. Each hypothesis has its merits, and it this stage it is not possible to opt definitively for one or the other. The first requires the boards to be smoothed individually on the paint side prior to assembly. The second leaves the smoothing largely till after assembly of the panel. In both cases it was essential to get the narrow sides of the boards absolutely straight to ensure a tight join. Roubo writes two centuries later: “We must also take care that the joins are straight along the full length of the boards, that they carry well on both sides […] because joins that are tight in this way prevent air from entering and stressing the panels. After making the joins with all necessary precautions […] they are glued […] and then the joins are heated so that the heat opens the pores of the wood, making them better able to take the glue, which finding them open clings to them and holds the joins […]. When the glue is hot, it is spread on the joint with a brush of boar bristles. The joins are then brought together and struck with a mallet.” 8 This method is no doubt similar for butt joints with pins and for tongue-and-groove joints. If the joiner was afraid of damaging the work with the mallet, he could just give small shocks to the panel by tilting it and letting it fall on the bench, on one side and then the other, and thus gradually have the tongue fit perfectly into the groove or the pin into the corresponding hole.