64685 2025 eng lecture 0 -- -- -- Historical plaster formulations offer valuable insights into advanced engineering in pre-modern cultures. This study examines two such gypsum-based recipes: Gach-e Koshteh from 14th-century Iran and Gesso Sottile from 15th-century Italy, both of which have unique characteristics and were essential for artistic and architectural decoration. By replicating these recipes in a laboratory setting, we demonstrate how traditional masters manipulated gypsum microstructure without additives to optimize the surface and mechanical properties of plaster for specific functional and artistic purposes. The Koshteh recipe involves intensive kneading during plaster hydration, which retards setting and produces a platelet-like crystal morphology with alignment of the {010} faces, resulting in a hydrophilic surface ideal for water-based wall paintings. Sottile, in contrast, relies on slow recrystallization in excess water, generating loosely packed, needle-like crystals with reduced wettability—suitable for oil-based painting and gilding. Using wide-angle X-ray scattering (WAXS), atomic force microscopy (AFM), and scanning electron microscopy (SEM), we reveal that the Koshteh recipe yields a denser, better-packed plaster with enhanced wettability, while the Sottile recipe forms larger, more loosely arranged crystals and a more hydrophobic surface. These findings underscore the ingenuity of historical materials engineering and offer valuable insights for modern conservation and sustainable restoration practices. 10.48380/4e5z-av91 Geo4Göttingen 2025 Göttingen, Germany 14.09.2025 18.09.2025 0 publish false true Tomasz Stawski eng uncontrolled Plaster eng uncontrolled Gypsum eng uncontrolled Stucco eng uncontrolled Cultural heritage Ingenieurwissenschaften und zugeordnete Tätigkeiten Sanitär- und Kommunaltechnik; Umwelttechnik 6 Materialchemie 6.3 Strukturanalytik Umwelt Umwelt-Material-Interaktionen Circular Economy Material Datei im Netzwerk der BAM verfügbar ("Closed Access") Präsentation Materialdesign