The "archaeology" of Old Master painting materials and techniques is often confronted with the lack of knowledge about certain raw materials that fulfilled a predominant role in the past. This is namely the case of white leather glue, recommended by the Portuguese Filipe Nunes in his 1615 Arte da Pintura. Symmetria, e Perspectiva for ground layers on easel paintings (canvas or panel), and on wooden statues; he considered it the only suitable glue for sizing and whitening before painting, as well as for making the bole for gilding to obtain a burnished gold. Depending on the sources, from Alcherius (1398) to Le Pileur d'Appligny (1779), some Old Masters also agreed with Nunes: a few judged white leather glue equivalent to parchment size, a few prized only the parchment glue, finally others used one or more glues from different origins. Either because the designation of such materials is liable to misinterpretation, or because their production ceased a long time ago and their trade secrets have been lost, these glues are mainly replaced today by the high-grade rabbit skin glue in experimental reconstitutions. It is a wholly accessible material, easy to buy in sheet form or reduced to powder. We found it pertinent to make a research on the composition of the white leather glue, and to compare it with both parchment and rabbit-skin glues. We were able to find the set of treatments applied, in the past, to the raw materials from which the glues proceed, by compiling the information provided by several painting treatises, the corporative regulations of crafts tanners and parchment makers between 1407 and 1768, as well as technical handbooks from the 18th and 19th centuries. White leather has been made by us according to ancient precepts, thanks to the collaboration of an old Portuguese tanner. Parchment, also produced according to Old Craft techniques, and rabbit-shin glue accessible in sheets, corresponding to the 19th Totin Frère production, were acquired in France and in Italy to enable comparison of these materials. White leather and parchment were examined with SEM (with SE and BSE imaging modes) on both sides (grain and flesh), in order to verify their technical treatments. They were also analysed by SEM-EDS, as well as the sheet of rabbit-skin glue, to put in evidence the elemental composition of the inorganic compounds used in their production. Finally, the glues were also analysed by the same method, to understand to which point such inorganic compounds have remained in them. The production of white leather glue would allow us to reconstitute the rich polychrome coating applied on the 17th-18th C religious sculptures in Portugal in order to test technical parameters, and physical and chemical behaviours. This experiment would also enable us to understand the contribution of this specific glue to the exceptional state of conservation of certain of those sculptures.
|Title of host publication||Proceedings of the International Conference held at Nicolaus Copernicus University, Toruń / 21-24 October 2010 / Toruń|
|Publication status||Published - 1 Jan 2012|
|Event||Parchment and Leather Heritage. Conservation-Restoration - |
Duration: 1 Jan 2010 → …
|Conference||Parchment and Leather Heritage. Conservation-Restoration|
|Period||1/01/10 → …|