Preventing the Undesired Surface Veiling after Nanolime Treatments on Wall Paintings: Preliminary Investigations

During the last decades, the discovery of nanolime and its introduction in the field of Cultural Heritage has entailed a significant advance for the consolidation of historic wall paintings. Nevertheless, its use is not completely generalized yet within the conservation practitioner’s community due to its undesired white veiling deposit on the surface after treatment which usually covers the pictorial layer. Given the scarcity of existing literature which specify how to mitigate this undesired side-effect, the aim of this work is to carry out the first assessment of possible cleaning and treatment methods to eliminate those deposits and, at the same time, to analyse their effects on the consolidation properties. To do that, we have developed laboratory fresco wall paintings specimens. After applying an artificial ageing cycle to all of them, we consolidated them with CaloSil IP25, one of the most currently used commercial product in the practice. The elimination of the whitish deposits has been investigated with different methods: (1) wiping off the superficial excess of product immediately after each application during the treatment; (2) mechanical cleaning (scalpel) after consolidation; chemical cleaning with rigid gels of water (3), ethylenediaminetetraacetic acid (EDTA) (4) and citric acid (5) after consolidation. The effectiveness of each cleaning method has been assessed by non-destructive methods before and after the consolidation, and repeated after cleaning, by measuring differences in colour, water absorption by capillarity (i.e., sponge test), superficial adhesion (i.e., Scotch Tape Test) and by quantifying the thickness of the deposits eliminated by means of photogrammetry. Results show that both the mechanical cleaning and the removal of the excess of product after each application during the treatment yielded the most promising results for conservation practice.Ministerio de Ciencia e Innovación, Gobierno de España, with the project PID 2019-105706GB-I00/SRA (State Research Agency/10.13039/501100011033).Marie Skłodowska-Curie (MSCA-IF) grant agreement No 893762 (NANOMORT

Lime based nanomaterials for the conservation of calcareous substrates in heritage structures

Nanolime is one of the most promising consolidation materials used in the conservation of historic calcareous substrates. Whilst the popularity of nanolime has grown significantly in the last two decades, its consolidation mechanism when applied to highly porous substrates still needs to be fully understood. The aim of this Ph.D. is to understand the consolidation mechanism of a number of nanolime products in highly porous substrates and to investigate new ways to improve nanolime consolidation effectiveness. The research consisted of six experimental programmes: 1) comparing the consolidation effectiveness of three available nanolime products (Nanorestore Plus®, Calosil® and nanolime synthesized following a method developed by researchers of the University of L'Aquila, Italy); 2) investigating the influence of different types of solvent on the consolidation effectiveness of nanolime; 3) investigating the influence of substrate pore structure and nanolime particle size on the consolidation effectiveness of nanolime; 4) investigating the consolidation effectiveness of nanolime on Biocalcarenite from Agrigento, Italy; 5) investigating the consolidation effectiveness of nanolime on Indiana limestone and weathered marble from the Smithsonian National Museum buildings, USA; and 6) investigating the use of additives to improve nanolime consolidation effectiveness. Nanorestore Plus® yielded the highest short-term consolidation effect, measured by means of a Drilling Resistance Measurement System, in both limestones and lime-mortars. However, L'Aquila nanolime showed a higher durability which was attributed to a better developed crystalline structure. A 50%-50% water-isopropanol solvent appeared to be the best option for dispersing nanoparticles synthetized through the L'Aquila's method as it yielded a higher consolidating effectiveness compared to other types of solvents. Results also suggest that due to the different size of their nanoparticles, Nanorestore Plus® could be more suitable to consolidate coarser substrates, while L'Aquila nanolime seems to be more suitable to consolidate substrates with a finer pore structure. Results also demonstrated that L'Aquila nanolime can be used effectively for the consolidation of the biocalcarenite from Agrigento and the weathered marble from the Smithsonian Museum. Furthermore, it was shown that the use of sticky rice in a combined treatment with L'Aquila nanolime improves the consolidation effectiveness although prolonged exposure to moisture can compromise treatment durability. Finally, results also showed that nanolimes yield a higher consolidation degree in substrates composed mainly of calcite (limestones) than in lime-mortars containing silica sand

The influence of using wet cellulose poultice on nanolime consolidation treatments applied on a limestone

Acknowledgments J.S. Pozo-Antonio was supported by the Ministry of Science and Innovation, Government of Spain through grant number RYC2020- 028902-I. J. Otero’s current research is funded by the European Commission on the Marie Skłodowska-Curie Actions (MSCA-IF) from the European Union’s Horizon 2020 on research and innovation, grant agreement N. 893762 (NANOMORT). Funding for open access charge was provided by Universidade de Vigo/CISUG.Consolidation treatment with nanolime is a common conservation intervention which needs more research to enhance penetration and mechanical properties while also minimizing the undesired white veil on the surface which significantly alters the surface appearance. In this light, the application of a cellulose poultice soaked in distilled water over the treated surface with nanolime tries to prevent the formation of white hazes and to favour nanolime carbonation and penetration in the pore structure. However, the real influence of this practice on the consolidation effectiveness has never been studied yet and is not yet well understood. In order to provide more insights about its most suitable application method, in this study, we investigated the effectiveness of a wet cellulose poultice for two different nanolime consolidation treatments on a weathered limestone. Nanolime has been synthetized by anion exchange processes and dispersed in two mediums: i) water and ii) 50% v/v of water and alcohol. The influence of the poultice on the penetration and aesthetic properties has been studied by drilling resistance measurement, ultrasounds test, stereomicroscopy, measurements of roughness and static contact angle, spectrophotometry and scanning electron microscopy (superficial and cross sectioned samples). Additionally, consolidation effectiveness has been evaluated through the changes in apparent density, open porosity, porosity network in the outer 5 mm of the surface by mercury intrusion porosimetry and surface cohesion by the peeling test. Results show that, contrary to what is usually assumed, samples where a wet cellulose poultice was applied after the consolidant reached the lowest penetration levels and retained lower dry matter in comparison to their counterparts without poultice. A consolidation treatment with nanolime is more complex that it is generally considered, and the application of poultices is not always enhancing consolidation level; the most suitable application procedure must be chosen with regards to the nanolime and substrate specific characteristics.Ministry of Science and Innovation, Government of Spain through grant number RYC2020- 028902-I.European Commission on the Marie Skłodowska-Curie Actions (MSCA-IF) from the European Union’s Horizon 2020 on research and innovation, grant agreement N. 893762 (NANOMORT)Funding for open access charge was provided by Universidade de Vigo/CISU

Heritage Conservation Future: Where We Stand, Challenges Ahead, and a Paradigm Shift

J.O.'s current research was funded by the European Commission on the Marie Skodowska-Curie Actions (MSCA-IF) from the European Union's Horizon 2020 on research and innovation, grant agreement no. 893762 (NANOMORT). The author thanks his professional mentors in Heritage Conservation Prof. A. Elena Charola (Smithsonian Institution, USA), Prof. Heather A. Viles (University of Oxford, UK), and Prof. Carlos Rodriguez-Navarro (University of Granada, ESP) who helped him in one way or the other to develop some of the critical reasonings included in this communication. The author especially thanks Prof. Koenraad Van Balen (KU Leuven, BEL) for initializing him into Prof. Ostrom's research, and in this novel ecosystem of production based on the commons and especially its possible impact on heritage conservation future. The view and opinions of the author expressed herein do not necessarily state or reflect those of the University of Granada, the European Commission, or the mentioned mentors.Global cultural heritage is a lucrative asset. It is an important industry generating millions of jobs and billions of euros in revenue yearly. However, despite the tremendous economic and socio-cultural benefits, little attention is usually paid to its conservation and to developing innovative big-picture strategies to modernize its professional field. This perspective aims to compile some of the relevant current global needs to explore alternative ways for shaping future steps associated with the 2030 Agenda for Sustainable Development. From this perspective, it is conceptualized how emerging artificial intelligence (AI) and digital socio-technological models of production based on democratic Peer-2-Peer (P2P) interactions can represent an alternative transformative solution by going beyond the current global communication and technical limitations in the heritage conservation community, while also providing novel digital tools to conservation practitioners, which can truly revolutionize the conservation decision-making process and improve global conservation standards.European Commission on the Marie Skodowska-Curie Actions (MSCA-IF) from the European Union's Horizon 2020 on research and innovation 89376