Gerardus Mercator (1512–1594), a cartographer, philosopher, and mathematician born in Flanders in 1512, devised a new type of map projection in which the Earth is represented on a cylindrical surface, so that nautical routes are plotted as straight lines. The General Atlas of 1585 comprises 73 maps on coated paper, printed using an intaglio process and illuminated. The maps are mounted on cardboard. It also contains an index of locations and a portrait of Mercator.
The most serious alteration to the book's structure was the oxidation of the paper caused by the oxidation of the inks, especially the green ones. In these areas, the fibers had lost their cohesion and the paper had become brittle, to the point of
Some maps had become detached and suffered considerable damage. Temporary lamination was essential to allow handling during the restoration process. The book block also showed general soiling, tears, creases, and some loss of support material. Only fragments of the endpapers remained.
The original binding was parchment over a cardboard core, stamped on the front and back covers with a large gilt rosette. The most worrying alteration was the breakage of the raised bands and stitching, jeopardizing the integrity of the work. The headbands had almost completely disappeared, although remnants of thread remained. The main alteration to the parchment was its dehydration; this caused cracks and losses of material that even left part of the spine of the book block exposed. Furthermore, as the parchment contracted due to dehydration, its dimensions had been reduced, so it no longer fully covered the book block.
Before the restoration process, it was photographed
The work was thoroughly examined, all traces of the sewing were recorded - veins and threads, stitches, sequence of signatures - and chemical analyses were carried out to determine the solubility of the pigments as well as the degree of acidity of the paper.
Indeed, deacidification proved to be the most delicate aspect of the process: the analyses revealed the pigments' high solubility, preventing us from applying a deacidification treatment by bath. However, deacidifying the substrate was essential as it could slow the oxidation process. We therefore opted for a dry deacidification treatment.
Lamination provided a second layer of support to areas of paper that, due to their extreme fragility, were at risk of detaching. However, even with very low-weight paper, lamination always produces a hazy effect, reducing the sharpness of texts or images. In the case of the General Atlas, the chosen approach was to laminate the reverse side of the maps, which only in some cases contained text, and, where possible, to perform partial laminations.
