Gelatine in Historical Paper Production and as Inhibiting Agent for Iron-Gall Ink Corrosion on Paper
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_1_04_26_39.doc |
| Abstract: | SUMMARIES. Since the beginning of papermaking in Europe gelatine has been used as a sizing agent in order to make the paper suitable for writing using aqueous ink and more resistant towards abrasion. Over six centuries the technology and quality of gelatine sizing has been modified. Generally, heavily gelatine-sized papers are more durable than those with weak sizing. A look at the hypothesis as to what amount the positive activity of gelatine is rooted in its capability to bind reactive metal, especially iron(II)-ions, which is a general quality of proteins, is taken with especial interest in its suitability to resize iron-gall ink manuscripts after an aqueous treatment. Accelerated ageing tests have demonstrated that resizing such manuscripts using gelatine has a significantly better blocking effect towards ink corrosion than the other resizing agents commonly used for paper conservation. CONCLUSION. Our results prove that sizing with gelatine may result not only in a mechanical, but also in a chemical stabilisation of papers written in iron-gall ink. Gelatine hasa considerable capacity to fix free iron(II)-ions present in unbalanced iron-gall inks, thus making them inert. Other sizing agents used in paper conservation, such as cellulose ethers or starch paste, do not have comparable properties. Therefore, the traditional sizing agent for historical rag paper, i.e. animal glue or gelatine, is to be strongly recommended as a resizing agent for aqueous treated iron-gall ink manuscripts (Fig. 3.) The best results can be expected from using gelatines of type B and of high or medium Bloom degree (> 200 g). A type B gelatine is produced under alkaline conditions from beef collagen. During production a typical molecular structure with characteristic reactive groups along the macromolecular chains develops. The Bloom degree determinates the jelly value and indirectly the degree of hydrolytic decomposition of a gelatine. Modern gelatines differ from historical proteinaceous glues by careful and controlled processing techniques and there are only small quality fluctuations19. A food quality gelatine is sufficient in purity (ash content <1%). A gelatine of type B, 220 Bloom, e.g., has a hydrolytically low decomposition because of its production conditions; it can form elastic films with a high capacity for binding free ions. At environmental pH >4.7-5.4, which is the isoelectric point of the gelatine, the molecular chains of such a type B gelatine have a high content of dissociated, negatively charged carboxyl groups, which may fix transition metal ions16. |
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| ISSN: | ISSN 0034-5806 |
