Freeze-drying of Water-damaged Paper Material
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_2_04_119_128.doc |
| Abstract: | SUMARRIES. The final goal of this work is to study the application of the freeze-drying process to water-damaged archival and library materials. Soaked samples, i.e. reams of modern blank paper (80 g/ sheet) consisting of sheets 42 X 59 mm, simulating water-damaged paper material, were prepared and subjected to two different procedures, i.e. pre-freezing and evaporative-freezing respectively. The temperature was monitored in different positions of the sample by means of wire-thermocouples; pressure was monitored by a Pirani gauge; the loss of water at different times of the process was measured by weight control. The qualitative result of freeze-drying was evaluated visually and tactically and found to be acceptable. The average residual moisture content was lower than the initial one (1.0 +- 0.5 %) indicating an over-drying. Since it was verified that primary and secondary drying overlapped, a further reduction of process duration was not possible Re-conditioning of rigid and brittle dried documents is recommended, in order to avoid mechanical damage. CONCLUSION. A procedure for preparing reproducible soaked samples of paper was defined and set. By soaking samples for 18 hours and draining for 5 hours, reproducible soaked samples were obtained; the amount of absorbed water was 121 +- 1 °/o in relation to the initial dry weight. The method was reproducible, simple and economic. The freeze-drying and evaporative-drying of soaked samples resulted in the complete drying of the paper in 18 hours, without excessive damage. Since primary and secondary drying overlapped, over-drying of paper occurred obtaining a dried product with a residual moisture content, which was below 1 °/o. With regard to antique documents, especially those containing miniatures or paintings, re-conditioning of dried, brittle paper is recommended, before handling. Since the present work has a preliminary nature, many simplifications were introduced, including the quality of the paper used (modern and blank) and the soaking media (distilled water). |
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| ISSN: | ISSN 0034-5806 |
