Damaged Blue Papers : Optimising Consolidation while Preserving Original Colour

International audienceThis article presents the case of blue paper in a sample book that once belonged to Victor Poterlet, a French wallpaper designer operating in Paris in the 19th century. Prussian blue is the main colourant used to dye the paper. The condition of the paper is very poor, probably due to the presence of free iron ions. However the paper could not be replaced or chemically treated because it supports 954 samples, which could not be dismantled due to time considerations. Moreover the paper is indubitably of high aesthetic value and an inherent part of the original. This study was carried out in order to optimise the reinforcement of the blue paper through local treatments, such as resizing and/or lining. Tests were also undertaken to evaluate improvements in mechanical properties induced by these treatments. In addition it was found necessary to estimate any colour changes that could result from the application of an adhesive to a deep blue paper. Several adhesives were evaluated: Tylose, Klucel, gelatine, starch, Funori, Lascaux 498HV and Lascaux 360HV. The best results were obtained with Tylose. Finally, the book was consolidated with linings that were applied by reactivating the adhesive. This method offered a satisfactorily compromise between the best reinforcement and the least colour chang