Dense carbon dioxide technologies applied to the conservation of cultural heritage: A review

Cultural heritage conservation is a complex and challenging field, involving a wide variety of materials with distinct properties, degradation behaviours and specific requirements, often demanding non-standardised methodologies. Conventional treatments frequently rely on hazardous products, raising concerns about user safety and environmental impact. In response, green chemistry principles have gained prominence, advocating for safer and more sustainable practices by replacing toxic products with less harmful alternatives, thereby mitigating risks to conservators, the environment, and heritage assets. Carbon dioxide (CO 2 ), owing to its tuneable and non-toxic properties, has emerged as a green solvent alternative to traditional solvent-based methods in the conservation field. Therefore, this research reviews the application of dense CO 2 technologies (liquid and supercritical) in conservation processes including cleaning, decontamination, degreasing, hydration, stabilisation, and consolidation, across a wide array of materials like textiles, wood, leather, metal, glass, paper and plastics. Drawing on experimental trials and case studies, key achievements, challenges, and emerging trends are highlighted, encouraging further research into these promising and sustainable CO 2 -based technologies. • Comprehensive review of liqCO 2 and scCO 2 application in heritage conservation; • CO 2 's potential for safer and greener conservation processes; • This study reviews trials, noting CO 2 method successes, limits, and research needs.