Freeze-drying and cultural heritage: An overview

This paper aims to provide an overview of the application of freeze-drying in the field of cultural heritage. The possibility of removing water from an object at low temperature, thus preserving most of its specific features that would be lost at high temperature, makes the process the elective choice when restoring water damaged materials. Flooded archives and libraries, due to natural events or to the intervention of fire extinguishing systems, are a typical case where freeze-drying can be applied since the material, after flooding, is brought to a low temperature as soon as possible to cause the water to freeze and, therefore, to block the degradation of the material. Besides, freeze-drying may be used to preserve archaeological finds, <i>e.g.</i> waterlogged woods or wet textiles, by means of water removal. Anyway, in all these cases specific issues must be faced, aiming to preserve the mechanical properties of the object, and this may require ad hoc pretreatments. It must be highlighted that in some cases the occurrence of a freeze-drying process, in particular of the atmospheric freeze-drying process, is undesired for the preservation of finds, and this must be carefully managed. Finally, the possibility of using freeze-drying to create works of art will also be addressed.

本文旨在概述冷冻干燥（freeze-drying）在文化遗产领域的应用。该技术可在低温条件下脱除物体内的水分，从而保留绝大多数在高温环境下会丢失的特有特征，因此成为水损材质修复时的优选方案。因自然灾变或消防灭火作业导致水淹的档案馆与图书馆，是冷冻干燥技术的典型应用场景：相关材质受淹后，需尽快将其置于低温环境以冻结水分，从而阻断材料的降解进程。此外，冷冻干燥还可通过脱除水分的方式，用于保存考古出土文物，例如浸水木材与潮湿纺织品。无论在上述何种场景中，均需应对特定技术难题，以保障文物的力学性能，这往往需要定制化的预处理工序。需特别强调的是，在部分场景中，冷冻干燥过程——尤其是常压冷冻干燥工艺——可能不利于文物保护，需进行精细化管控。最后，本文还将探讨利用冷冻干燥技术创作艺术作品的可能性。