| Abstract: | Summaries. Two papers, a porous ligneous unsized book paper and a heavily calendared, lignin-free, sized ledger paper, were coated with parylene-N and then subjected to standard water washing, bleaching or deacidification treatments. Two sets of single-sheet papers were coated: one at normal pressure to yield a coating of average porosity and one at high pressure in order to produce a more porous coating. The following conditions were used for the conservation treatments: pure water (washing); 2 % peroxide, pH 9.0, stabilized with EDTA (bleaching); and 1 000 ppm magnesium bicarbonate (deacidification). Uncoated and untreated control samples were included in all of the experiments. The effects of the conservation treatments were determined by-carrying out colour (Tappi brightness, L'a'b, and Delta E), strength (zero-span tensile strength) and pH (Tappi cold extraction) measurements before coating, after coating, and after conservation treatment. Results indicate that both types of parylene coating increased the strength of both papers but had a larger effect on the porous ligneous book-paper. Aqueous washing and bleaching treatments had small or no effect on the colour and strength of all Parylene-coated papers. The deacidification treatment was more successful: the acidity in the coated ligneous paper was partially neutralized while the ledger paper was completely neutralized and left with a small alkaline reserve. Experiments also were carried out to determine the distribution of parylene-N in papers which had been coated while bound in a standard cloth-covered book format. Film thickness was determined at IR baseline interference ripple which is a much more precise method than absorption. Books of various sizes containing ligneous wood pulp, non-ligneous wood pulp, or rag fibres were included. The papers studied were sized or unsized, coated or uncoated. The results show that film thickness was smallest in areas in pages in livres de differents formats contenant de la pate de bois avec ou sans lignine ou des fibres de chiffon ont ete etudies. Les papiers etaient encolles ou non, impregnes ou non. Les resultats montrent que l'epaisseur du film etait plus faible au milieu du livre dans les zones des pages situees pres de la charniere. L'epaisseur dufilm augmente lorsqu'on va vers le bord des pages et vers les premieres el dernieres pages du livre. Les resultats indiquent que les livres intacts ne peuvent etre impregnes de facon homogene et il est douteux que cela soit en fait souhaitable. Une meilleure repartition de parylene est observee apres traitement de simples feuilles. the middle of the book near the gutter. Film thickness increased as one progressed to the edges of individual pages as well as to the front or back pages of the book. The results indicate that intact books cannot be coated evenly and it is doubtful if this is actually desirable. A more even Parylene distribution is observed when treating single-sheet artifacts.
Conclusions. Based on the work reported in this article, the following conclusions and comments can be made regarding the Parylene treatment of book and paper materials. 1. Parylene strengthens a wide range of paper types. For films up to 6-7 microns, the amount of strengthening is dependent upon the thickness of the coating deposited on the surface. 2. The distribution of Parylene deposited on intact books is controlled by the accessibility of the various areas of the object. The locations which are normally weakest (e.g. edges of pages) receive the thickest coating while the spine and gutter does not receive a significant amount of polymer coating. 3. Parylene coating of bindings results in excellent consolidation of leather degraded by red-rot. 4. It is possible to deposit a relatively even coating of Parylene on single sheets of paper. 5. The surface area of the substrate controls the weight of Parylene deposited during coating. Unsized, porous papers receive much more Parylene than do smooth sized materials. 6. The principal disadvantages of Parylene are visual changes to coloured media and interference patterns which change the appearance of dark or glossy surfaces. 7. Deacidification of Parylene-coated paper can be carried out successfully, especially if the paper is smooth. 8. Parylene deposited under high pressure" results in a marginally more porous film. |
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