Different low-cost materials to prevent the alteration induced by formic acid on unstable glasses

• Published in: Heritage science 2021-11, Vol.9 (1), p.1-16, Article 142
• Main Authors: Arévalo, Rodrigo, Mosa, Jadra, Aparicio, Mario, Palomar, Teresa
• Format: Article
• Language: English
• Subjects: Acids; Activated carbon; Alteration; Chemistry and Materials Science; Degradation; Desiccators; Exposure; Formic acid; Glass; Low cost; Materials Science; Museum; Optimization; Research Article; Showcases; Silica gel; Silicon dioxide; Sorbents; VOCs; Volatile organic compounds
• ISSN: 2050-7445; 2050-7445
• DOI: 10.1186/s40494-021-00617-x

The most frequent cause of glass degradation is environmental moisture, which is adsorbed on its surface forming a hydration layer that induces the rupture of the glass network. This pathology is accelerated by the accumulation of volatile organic compounds (VOCs), like formic acid. Although there is extensive knowledge about their impact, concentrations inside display cases are difficult to reduce efficiently. This study presents the assessment of different materials to reduce the concentration of formic acid to mitigate the degradation produced in unstable glasses. With this objective, copper threads, steel wool, silica gel, and activated carbon were chosen as low-cost materials with good adsorption or reactivity to the VOCs, exposing them in desiccators to an environment of 100% RH and 10 ppm of formic acid. Given that silica gel obtained the best results, its optimization as a sorbent material was evaluated by maintaining, regenerating, or renewing it when exposed next to the same glass. The tests carried out concluded that the hygroscopic capacity of the glasses exposed with silica gel decreased and, therefore, a lower degradation is observed on its surface. In addition, regenerating and renewing weekly the silica gel improved the results.