Old materials, new ideas: the use of concentrated solutions of hydroxypropyl cellulose to remove an aged glossy varnish on a Seventeenth Century Dutch map

Abstract

The Bonaparte Tasman Map is a hand drawn map on paper in the collection of the State Library of New South Wales (SLNSW). Before treatment, crack, creases, and folds on the map’s surface formed a unique combination of deterioration features. The complex 3D shape created by differential paper drying and a glossy varnish produced a chaotic pattern of bright highlights that obscured the cartographic and graphic ornamentation and conspired to discourage any observers interested in the map. A safe method was developed to reduce the glossy varnish. Published experimental data informed the final treatment method by providing reference flow curves and a set of viscosity control variables. The dissolution of the glossy varnish was achieved by impeding the flow of solvent from the viscous hydroxypropyl cellulose solution into the varnish with applications of 7wt% to 10wt% (1 000 000 molecular weight) through a barrier layer of porous abaca tissue. The main findings were the need for a greater hydroxypropyl cellulose concentration and molecular weight, than those generally recommended in conservation. And the relationship between polymer entangled and non-entangled state, the flow movement generated by a shear force and the subsequent controlled release of solvent molecules.

Keywords:

• Hydroxypropyl cellulose polymer
• viscosity
• natural varnish
• map
• varnish removal

Acknowledgements

The author is very grateful to Dennis Dwarte for his invaluable contribution to all mathematical calculations. To the Staff of the State Library of New South Wales.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Dana Kahabka

Dana Kahabka is a Conservator, at the State Library of New South Wales where she has worked for 21 years on a range of collaborative projects including establishing a cold storage facility for photographic material; in role of Senior Conservator, Digitisation Project developed a preservation tool by automating the measurement of paper yellowing from every page in a digitised book that graphically could represent the aging profile of a book; investigated the structure of pith paper to understand the treatment and handling implications of a botanical cell structured material. Previously Dana has worked at a number of cultural institutions including the Australian War Memorial, Queensland Art Gallery, The National Archives of Australia (Sydney Office), the State Library of Queensland and the Australian National Maritime Museum. Dana undertook an internship at the Centre for Cultural Materials Conservation, University of Melbourne after completing a Bachelor of Applied Science in the Conservation of Cultural Materials from the University of Canberra.