Effect of pH and Carbonyls on the Degradation of Alkaline Paper Factors Affecting Ageing of Alkaline Paper
| Hlavní autori: | , , |
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| Médium: | Článok |
| Jazyk: | angličtina slovenčina |
| ISSN: | ISSN 0034-5806 |
| On-line prístup: | http://www.viks.sk/chk/res_3_02_145_153.doc |
| Abstrakt: | CONCLUSION. Results indicate, that high pH triggers an increased degradation of samples made from bleached chemical pulps during accelerated ageing. Samples of bleached chemical pulps with no additives, deacidified using magnesium bicarbonate solution seemed to show ageing instability. Such a paper however, is never used as information carrier and is therefor never the object of deacidification in conservation workshops, as paper made from these pulps always contains additives, which lower the pH and thus increase the stability during ageing. In contrast to the bleached chemical pulps, the rag papers and papers made from purified cotton fibers tested in our study, do not appear to exhibit the same pH sensitivity during the standard accelerated ageing conditions. Nevertheless, caution is required when deacidifying paper made from bleached chemical pulp using magnesium bicarbonate, until the behaviour is confirmed for several other paper samples and ageing conditions. In addition to paper degradation, other factors, such as lightening of iron gall ink when deacidified using magnesium bicarbonate should be considered. SUMMARIES. Paper is a composite material, which makes interpretation of experiments extremely difficult. Nevertheless, the data obtained so far on a limited amount of samples support the theory that higher pH values may have a negative effect on the stability of paper made from bleached chemical pulps. Higher pH accompanied by higher ageing instability was obtained for bleached chemical pulps deacidified with magnesium bicarbonate compared to calcium hydroxide. However, the additives in paper may cause a marked decrease in the pH of the magnesium carbonate containing samples, resulting in less degradation in samples containing magnesium carbonate than of its calcium analogue. Contrary to the bleached chemical pulps, rag paper and paper made from purified cotton fibres do not exhibit pH sensitivity during the standard accelerated ageing conditions. |
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| ISSN: | ISSN 0034-5806 |
