Testing historic documents for potentially harmful copper-containing inks
Over time, metals present in gall ink oxidise contribute to the deterioration of the paper on which the ink was used. Consequently, conservators must identify which of the documents in their collections have been created with gall ink. The problem they face is how to make this determination without harming the document. The organisations involved in the INKCOR project sought to provide conservators with the necessary tools to make this assessment. Specialists from the Netherlands Institute of Cultural Heritage focused their efforts on the detection of copper, the second most important metal in gall ink after iron. A simple non-bleeding indicator test was developed using the organic compound 2-(5-nitro-2-pyridylazo)-1-naphtol. The presence of copper is revealed by a change of colour in the indicator strip. The test is easy for conservators to perform and is only slightly less sensitive than the more advanced laboratory-intensive methods (e.g. Proton Induced X-ray Emission) evaluated during INKCOR. Since the test is non-destructive, it can be used directly on originals. The Netherlands Institute of Cultural Heritage is looking to share this new development with the museum and conservation community.
