AN AGAROSE GEL-BASED APPROACH FOR THE REMOVAL OF METALLIC-BASE INK STAIN FROM THE PAPER SURFACES OF A 17TH CENTURY BOOK

Removing ink stains from the pages of ancient and valuable books is a very challenging and sometimes impossible task. Only in some circumstances, restorers are able to improve the appearance of an ink-stained page by lightening the spots using an ink eradicator. This paper reports on an approach for the removal of ink stains from a 17th century book using a combination of two commercial houseware products, the rust remover for textile and bleach. The products were chosen on the basis of their active ingredients such as hydrofluoric acid (HF), which facilitates the removal of metal ions contained in the inks (such as iron and chromium) and sodium hypochlorite (NaClO), known for its whitening abilities. The products were first tested by direct application to one of the several stained pages as a control experiment. The ink stain was successfully removed from the book, but by SEM analysis the page results in a clear detachment of the cellulose fibers from the paper pulp, which reflect a significant change in the paper fine structure. Moreover, the mixing of chemicals occurring during this procedure generated toxic vapors and the entire protocol could only be performed under a chemical fume hood. A new procedure was developed to mitigate these negative effects. Each of the two commercial products was dispersed in a 2% agarose solution shortly before its gelification and the two gels thus obtained were applied consecutively on the surface of the paper to be cleaned. The results showed an effective removal of the ink stain from treated page, avoiding irreparable damage to the paper structure and improving the working conditions of the restorers. Hence, the proposed gel cleaning procedure offers three main advantages: i) a simple and practical tool for effective removal of metallic ink stains from the paper surface; ii) reduction of damage caused by aggressive reagents (HF and NaClO) contained in cleaning products for a better conservation of paper fibers; iii) a great decrease of the risk of accidentally exposing the operators to harmful toxic vapor (produced by accidental mixing of aforementioned chemical reagents).