Nanomaterials for the cleaning and pH adjustment of vegetable tanned leather

Leather artifacts in historical collections and archives are often contaminated by physical changes such as soiling, which alter their appearance and readability, and by chemical changes which occur on ageing and give rise to excessive proportion of acids that promote hydrolysis of collagen, eventually leading to gelatinization and loss of mechanical properties. However, both cleaning and pH adjustment of vegetable tanned leather pose a great challenge for conservators, owing to the sensitivity of these materials to the action of solvents, especially water-based formulations and alkaline chemicals. In this study the cleaning of historical leather samples was optimized by confining an oil-in-water (o/w) nanostructured fluid in a highly retentive chemical hydrogel, which allows the controlled release of the cleaning fluid on sensitive surfaces. The chemical gel exhibits optimal viscoelasticity, which facilitates its removal after the application without leaving residues on the object. Nanoparticles of calcium hydroxide and lactate, dispersed in 2-propanol, were used to adjust the pH up to the natural value of leather, preventing too high alkalinity which causes swelling of fibers and denaturation of the collagen. The treated samples were characterized using Scanning Electron Microscopy (FE SEM), controlled environment dynamic mechanical analysis (DMA-RH), and infrared spectroscopy (ATR-FTIR). The analytical assessment validated the use of tools derived from colloid and materials science for the preservation of collagen-based artifacts

La chimica dei nanocomposti e la loro applicazione al restauro dei manoscritti

Cellulose-based artifacts are susceptible to fast degradation due to the presence of detrimental components and to the action of environmental pollutants. As a result, the acidity of pristine material increases, promoting the acid-catalysed depolymerisation of cellulose that alters the mechanical properties of paper. In this paper, the use of innovative dispersions of alkaline earth metal hydroxide nanoparticles will be discussed as a method of counteracting the degradation of paper. The application of the most recent formulations of nanoparticles dispersions for the deacidification of artworks will be highlighted. Finally, the usage of innovative gel formulations for the cleaning of cellulose-based artworks will be discussed