Abstract:The Justus Perthes collection of historically valuable maps, dating from late 18 th century to the 1960s, was acquired in 2003 by the State of Thuringa and given to the University and Research Library Erfurt/Gotha. The collection consists of more than 185,000 objects, of which 90 % have a format equal to or smalle r than 96 by 135 cm. Only 10 % of the maps are much larger in format. The maps are etchings, drawings, lithographs and prints, many of them carrying valuable inscriptions in different media -pencil, crayon, chalk, water colour, gouache and writing ink of diverse composition. The whole collection suffered from contamination with dust particles with a particle size of ≤ 1µm that are harmful upon inhalation and therefore regarded as dangerous for users. To make the collections accessible, the dust contamination was to be diminished to values below the maximum threshold value. A new kind of equipment was engineered that automates the cleaning operation of maps. The cleaning operation could be performed with a speed of 80 it ems per hour based on a size of 1 m width and a 1.5 m length. Maps are hand fed into a machine, where surface soiling removal is realized by electrostatic foils that are brought in contact to both sides of the maps w ithout any slippage, thus avoiding mechanical impact on th e objects' surfaces. In the period from July 2008 to August 2010 about 177,000 individual items, that is 96 % of the collection, underwent successful sur face cleaning and currently are made accessible to r eaders. The automated cleaning exceeded the expectations as far as treatment efficiency and treatment quality is concerned. The risk of mechanical damage that resulted from failures in the feeding and transport system was with less than 0.04 % extremely low. Even fragile and brittle objects passed the system without any observable mechanical damage. The technique can therefore be regarded as having a very gentle impact on delicate materials, and offers in selected cases an alternative to the conventional manual surface cleaning of paper-based objects.

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Airflow drying has originally been applied in printmaking and hand papermaking workshops in order to shorten drying times and maintaining planarity of paper. The technique was already suggested by R. Futernick in 1988 and was first introduced to paper conservation at the Western Regional Paper Conservation Laboratory in San Francisco. In this contribution, the physical basics of the drying process, including a simple drying stack prepared from corrugated board, are described. Drying is carried out in stacks of archival-quality corrugated cardboards and other paperboard materials under slight pressure. The stack of cardboards is equipped with a blower that provides a continuous airflow through the open channels of the card boards. The water is removed from the stacks by continuous evaporation through the moisture absorbing board until equilibrium with the ambient air is reached.

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