Application of Seven Borane Complexes in Paper Conservation
| Main Authors: | , , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0034-5806 |
| Online Access: | http://www.viks.sk/chk/res_4_00_213_228.doc |
| Abstract: | SUMMARIES. Seven borane complexes were tested for aqueous and non-aqueous conservation treatments of paper. All the reducing agents gave very good results when used in aqueous solutions with an effectiveness of 66 ˙*˙ 88% before ageing and 30 -+- 52% after 28 ageing days. The best results were obtained from borane ammonia complex (AB), borane tert-butylamine complex (TBAB) and borane N,N-diisopropylethylamine complex (DIPEAB). The latter, unfortunately, leaves an unpleasant residual odour on the treated papers. AB and TBAB can also be used in organic solutions, enabling the treatment of graphic media soluble in water. CONCLUSION. All the tested reducing agents gave very good results when used in aqueous solutions (Table 3). In organic solvents only AB and TBAB, the former in ethanol the latter in ethanol and in toluene, are able to exert their reducing power. The other reducing agents, except for TMAB in chloroform, are not active (Table 4). pH values of the aqueous solutions of all the reducing agents studied are high enough to alkalinise the paper, without inducing alkaline degradation (Table 1). The aqueous reduction of oxidised papers, followed by ageing (simulating the ageing of a restored ancient paper) offers a good protection with regard to the formation of oxidised groups, when compared to the oxidised unreduced papers. Obviously, borane compounds are not able to hinder the further intrinsic degradation of the paper, but the initial low amount of carbonyl groups prevents the fast increase of oxidised functions. From carbonyl content data we can see that the treatment of oxidised papers with reducing agents has an effectiveness of 66% up to 88% before the ageing and an effectiveness of 30 up to 52% after 28 ageing days (Table 6). Furthermore, the samples treated thus are found to be thermally more stable5,8. Concerning the optical properties, it is possible to see from Table 5 data that the best behaviour is shown from papers treated with borane-ammonia complex (AB) and borane tert-butylamine complex (TBAB). The yellowing of the papers treated with borane dimethylamine complex (DMAB; and borane N,N-diisopro-pylethylamine complex (DIPEAB) is faint: it is observable only instrumentally and not visually. We remember that the yellowing effect is especially measured by the increase of the b* co-ordinate, the decrease of the luminosity (L* co-ordinate) being less important for originally white papers. All experimental data point out, in conclusion, that treatments using reducing agents with all the studied borane compounds in water protect the paper against ageing and oxidation. The best results were obtained for AB, TBAB and DIPEAB. The latter, unfortunately, leaves an unpleasant residual odour on the treated papers. AB and TBAB can also be used in organic solutions, i.e. they can be used on water soluble graphic media. They were in fact employed in the restoration of De Nittis graphic works, performed in collaboration with the Istituto Nazionale per la Grafica9,10, in a simultaneous treatment of alcoholic deacidification and reduction of some unbounded books of the Liebig's Annalen belonging to the Department of Chemistry, University of Rome "La Sapienza11 and in the treatment of three De Chirico lithographs. |
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| ISSN: | ISSN 0034-5806 |
