Frystorkning Kontrollerad torkning av kulturhistorisk dräkt?

Abstract

Cultural objects may become wet by deliberate water cleaning, water disaster or water soaked for other reasons. Air drying textile objects and even other organic materials from a water wet state, involves many problems depending on the strong capillarity action of water. Damages and changes such as bleeding of dyes, stains or lines of impurities from water movement, shrinking or stiffness can occur. Freeze-drying as an alternative drying method has often been used for wet archaeological and marine objects, but more seldom for historical materials. This bachelor thesis addresses the issue of whether freeze-drying can be an alternative controlled drying method for historic costumes. Costumes and related objects are often composite objects, consisting of multiple materials, as well as being three dimensional, all of which will complicate drying. The purpose of this study was to investigate whether it is possible to handle costume objects after wet cleaning for drying by freeze-drying, and if damages due to surface tension of water, can be avoided in this way. A literature survey was carried out into the characteristics of water, the processes of wetting and drying, the properties of textile and skin, alternative drying methods and the theory of freeze-drying. Another aim of this thesis was to develop a practical procedure based upon experience. Seven case studies are reported. All objects are Sámi costumes: four “gákti”/clothing and three “gahpir”/caps made of textile, with some skin details. The freeze-drying process was carried out without vacuum in an ordinary freezing room. Different procedures and handling of the objects were tested from wet state through freezing, freeze-drying, and to the final air drying. Changes in dimension, colour and staining from water movement was evaluated afterwards. Observations were carried out during the whole drying process on the drying behavior. Appropriate drying equipment and how to decide the drying rate are discussed. The results suggest that freeze-drying can be an alternative drying method and a way to control the drying of historic costumes after wet cleaning. Damages due to air drying should in most cases be avoided by freeze-drying. A method to handle objects before freezing was investigated, in which the goal was to keep the object as wet as possible prior to placing in the freezer. This reduced the risk of damage from water movement and also the pressure of time. Some guidelines are given for practical use.