Improving access: Multi-analytical survey of the Norwegian Sea trade archive to establish storage conditions, digitisation priorities and conservation treatments

Abstract

The Norwegian Sea Trade Archive (NST Archive) from the University of Bergen Library, Norway, is part of the UNESCO documentary heritage and contains unique documentation of the activity of companies that traded in stock fish in Norway and Europe (16th-20th century). The archive consists primarily of bound paper manuscripts written mostly in brown ink. We have surveyed this collection using a multi-analytical approach focused on the material characterization and condition of the paper carrier and inks. Our main aim was to support decision-making on establishing storage conditions, digitisation priorities, and type and extent of conservation treatments necessary to make the collection accessible.

After a first visual examination to detect and quantify damages, for the paper support analysis we measured surface pH, paper thickness and water absorbency. Additionally, on a quarter of all tested materials, we performed a SurveNIR analysis, providing information regarding paper pulp type, lignin, protein and rosin content, degree of polymerization, and mechanical properties. The archival material was grouped into three periods characterising the three milestones in paper production: handmade gelatine-sized rag papers, machine-made rag papers with gelatine and rosin sizing, and papers made from processed wood pulp.

Regarding the manuscripts’ inks, we used iron and copper tests to determine the presence of Fe², Cu²⁺ and Cu⁺ions, respectively. For the visual characterization and condition rating of the inks, we used the protocols described by the Netherlands Institute for Cultural Heritage. The variety of ink colours and thickness of the inked lines encountered in each document was noted down. Thus specific tendencies present in each historical period became apparent. Results of the solubility of ink in water and alcohol significantly narrowed treatment options.

General tendencies of paper and ink degradation based on differences in papermaking were observed. Surface pH measurement, SurveNIR pH, rosin and protein concentration data showed that most rag papers were of poor to fair quality (pH ≤ 6.0 and low protein content (< 5 %)). Rosin-sized papers dated after 1840 had a lower pH (from 3.3 ± 0.2 to 5.0 ± 0.2) compared to gelatine-sized ones. Based on the obtained results, the overall condition of all the papers is good – slightly damaged but stable. The inks are not severely corroded, and there is no loss of text, although 20 % of the collection does show signs of iron-gall ink (IGI) corrosion. A limited number of documents, mostly before 1800, would require local antioxidative treatment. Due to the low pH of all the papers and the detection of ink corrosion, the collection should be stored in a cool environment, with low relative humidity.

After the survey, digitisation priorities were also established.