The objective is to determine the effects of air pollutants and climate, especially their synergistic effects, on the stability of cellulose materials, in particular on the paper based materials used and stored in museums, archives and libraries.
Test chambers have been employed to investigate the effects of nitrogen dioxide and sulphur dioxide on newly manufactured and aged papers. Deposition of sulphur dioxide was higher in papers with additives, particularly calcium carbonate, than in pure pulps. Deposition of acid pollutants was dependent on the capacity of the paper to buffer the acid species. Deposition of sulphur dioxide declined with increasing acidity but was enhanced in the presence of nitrogen dioxide. The exposure of papers to these air pollutants caused an increase in the acidity, the total organic carbon (TOC) value, the conductivity and the copper number. This means that the paper was degraded into water soluble organic compounds. There was also deposition of inorganic compounds on the paper. The decrease of the carboxyl groups and changes in the mechanical properties of the papers show not only a decarboxylation reaction (possibly the Ruff degradation mechanism) but also a direct effect on the degradation of the paper.
The effects of deacidification have been studied on modern and old papers. Two methods studied are the gas phase diethylzinc (DEZ) process and the solvent based process employing magnesium butoxytriglycolate. Papers treated with the latter had a strong, unpleasant odour while those treated with the former had a slight odour. The inks of documents deacidified by these methods were not affected and no depositsof salts were found although a slight yellowing was occasionally noted.
An important part of our cultural heritage consisting of cellulose materials is threatened by accelerated deterioration. The causes of this damage can be divided into 2 categories: internal factors, such as the used raw materials and the manufacturing process; and external factors, for example the storage conditions and air pollutants.
A representative number of paper grades are selected and reference papers are manufactured. Thus, old and aged archive papers and books are studied as well as freshly manufactured materials.
At present, most of the deterioration effects are attributed to the acidification of the materials; therefore deacidification is recommended. However, the effects of the deacidification process, and especially the effects of air pollutants on deacidified materials, are largely unknown. The following questions are investigated in this project:
the synergistic effects of various air pollutants on the stability of the selected materials;
whether combinations of air pollutants cause an accelerated deterioration of old and naturally aged materials as well as of deacidified materials;
the threshold level or response surface of the air pollutants (ie at what rate of deposition does accelerated deterioration occur);
the resistance of old paper (books) to air pollutants;
the internal effects of the papergrades in combination with air pollutants on the future stability;
and the efficacy of the selected commercial mass deacidification processes.
After evaluating these questions, recommendations will be provided concerning: the future stability; the best storage conditions; and the usefulness of deacidification.
Funding SchemeCSC - Cost-sharing contracts