Professor Germana Barone, University of Catania
The constant mission of all stakeholders involved in museum management is to make the best use of their collections – understood as Cultural Heritage – and ensure the greatest enjoyment from them. It is equally important, now more than ever, to make museum visits easily manageable, participatory and inclusive, devising measures to make the visit immersive and accessibile to all types of public. For example, a museum which is inclusive as regards blind or visually impaired visitors must tailor visits to their tactile requirements. Since they are recognized as Cultural Heritage assets, the artifacts which make up museum collections – historical and artistic, but also scientific – are often protected by strict regulations which prevent them from being touched, moved, or even photographed. This makes it impossibile for people with sensory deficits of a visual nature to partake of the enjoyment which a museum affords – the knowledge sharing, but also the emotions and sensations which a museum visit can kindle.
This communication gap can be bridged by using copies of works of art or of any object of cultural interest. However, in many cases the sensory experience remains partial because an accurate perception of the nature of the materials is lacking. The textural characteristic of different materials such as marble, stone, pottery, is obliterated by the use of “anonymous” materials for replicas, like plaster or the plastics which fail to render the unique tactile experience. Hence the need to use new materials which both make it possible and easy to create copies of the artifacts, and, at the same time, enable their surface characteristics to be faithfully reproduced. In the case of stone material it would be necessary to use a “liquid stone” which solidifies like a cement in moulds of any shape or size.
With this aim in mind, it has become increasingly important to make a rational choice of materials with which to make copies. In today’s world, the search is on for new materials which are environmentally sustainable and which foster the circular economy through the use of natural and/or industrial waste in order to implement the Energy Transition process promoted by EU policies. This scenario includes alkaline activated materials, more commonly known as “geopolymers”, inorganic materials which resemble natural stone materials such as rocks, and artificial materials like mortars and ceramics.
The geopolymers are formed through a chemical process which involves mixing an aluminosilicate powder and an alkaline solution. Unlike traditional materials, which often require heat treatment with temperatures of up to 1350°C, these new products are made at room temperature, without the use of ovens, with the further advantage of reducing carbon dioxide emissions into the atmosphere. Moreover, natural waste or waste from industrial production processes can be used, significantly reducing the extraction of natural raw materials.
Depending on the field of application, it is possible to obtain materials and artifacts with different physical and mechanical properties and to vary colour and texture. In fact these are extremely versatile materials which can be adapted for use in high-tech or niche fields such as restoration, establishing themselves as valid alternatives to traditional materials while remaining compatible with them from both a technical and aesthetic viewpoint.
In recent years, thanks to our active involvement and management of the PNR project “Advanced Green Materials for Cultural Heritage”, we have not only succeeded in the research and development of alkaline-activated materials by using natural and industrial Sicilian waste, such as volcanic ash from Etna and ceramic waste, but in their successful application at pilot sites of considerable historical and artistic interest. Geopolymer mortars were tested and applied in the restoration of detached mosaic tesserae in the Cathedral of Monreale (PA) as well as in restoring the worn and damaged brickwork of the Catania Odéon. Geopolymer bricks were produced and used to build a prototype of a small wall in imitation of the original masonry of the Odéon, and a prototype of a lava stone capital was also made at the same site, again using polymers.
Judging from these experiences, and bearing in mind the enormous potential of such materials, it is not difficult to imagine their being used in more specific contexts requiring the reproduction of museum artifacts which can be touched and handled. As we mentioned, at present the materials commonly used for this purpose are polymers and resins which, by their very nature, cannot reproduce the textures of the original material. This difficulty can easily be overcome by the use of alkaline-activated materials. By juggling with the chemical components and with the moulding process, it is possible to obtain objects with different shapes and surfaces – smooth, rough, porous, with added fibres and tangible aggregates. Furthermore, the versatility of these materials allows us to envisage making museum reproductions with the same raw material as the originals, thus enhancing the emotional involvement of the user. A propos of which, it is possible to make faithful reproductions of ceramic artifacts of archeological interest, exhibited in museums, by using, for instance, ceramic waste from the manufacturing sector; or epigraphs and marble statues by using natural precursors such as metakaolin or pumices. In addition, where necessary, the colour can be modified by using mixes containing several precursors so as to reproduce, for example, veined polychrome marble.