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Paper and papered seals
The very hygroscopic nature of paper seals makes them susceptible to varying conditions of humidity causing the impressions to shrink or expand thus weakening their structure. The ostie (wafers) are an amalgam containing copper based pigments and according to the literature can determine decay of the paper above and underneath the supports due to the interaction between the metal ions of the colouring agents and the supports. Indeed, these ions can catalyse cellulose decay. Likewise, unsuitable conditions of humidity and temperature can cause the proliferation of pathogens that damage the wafers as well as the paper layer.
Excessive artificial light and sunlight also cause decay of paper seals, and markedly accelerate it if associated with high humidity and temperature.
Papered seals are endangered by the same environmental conditions of incompatible temperature and humidity described for the two materials, wax and paper, they are composed of.
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Paper seals are restored using the methods used for paper. Hence, we adopt standard procedures to restore the fragile parts and to reattach seals to the writing support using adhesives when required. During paper seal restoration we pay great care to avoid any water-based interventions that damage the relief on the impression.
Scarce information is available in the literature for the restoration of papered seals. The procedure is more complex due to the presence of two materials.
The restoration of the wax may be hampered by the superimposed layer of paper and it is not always possible, and ethically correct, to attempt partially removing the wax layer to facilitate intervention. Indeed, such a procedure increases the risk of scattering traces of melted wax through the paper fibres.
Even the practise of total detachment of the seal that many restorers occasionally perform to facilitate restoration is an unacceptable method, especially in the field of diplomatic archives.
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