New Shading Technique Revealed through Reconstructing the Sgraffito Technology used North of the Alps during the Renaissance

Abstract

Research focusing on the 16th century original Renaissance sgraffito techniques has been in progress since 2012. It aims to specify the techniques utilized by sgraffito makers and to provide an evidence for the process by scientific methods. Primarily, the research concentrates on the area of South Bohemia. Non-invasive visual observation and documentation under the raking light illumination formed the basis of the investigation, complemented with laboratory material analysis. Based on the investigation, some characteristic features of Renaissance sgraffito were identified in the surveyed area and it led to a description of two specific methods of shading – coloured with a brush and smoothened by a trowel, so-called ‘trowel shading’. Both techniques work with middle grey tones and this visually interconnects sgraffito with monochromatic chiaroscuro painting. Detailed analysis carried out on two selected shaded sgraffiti from towns of Telč and Slavonice characterised the used raw materials, mixing ratios, and character and thickness of individual layers. Based on the analysis, local sources of materials were identified and subsequently, material copies were prepared with the aid of knowledge concerning historic lime production and processing technologies. The replicated mortar mixtures were evaluated on trial panels (workability, application methods, various surface finishes, setting and hardening, duration of time breaks between individual layers and/or scratching). The practical trials proved the connection between properties of the used materials (that predefined the use of the artistic technique including the ‘trowel shading’) and the final appearance of sgraffito decorations. Materials and technological copies facilitated a reconstruction of the Renaissance sgraffito technique originally used in the surveyed region and the newly gained knowledge and skills were subsequently used to restore a sgraffito façade in Slavonice.