How to identify the ink?

Metal components of historical inks were non-destructively identified using XRD and PIXE. Especially PIXE, due to its non destructive nature, high sensitivity (ppm detection limits) and high rate of data accumulation has recently proven as an invaluable tool in identification of metal tannate inks.

Due to a high-tech set-up requirements, such as the need for a linear accelerator capable of producing a 2.5 million electron volt (MeV) proton beam, the technique may not be used for rapid, on-site identification of inks by conservators. However, the Ion Beam Analytical (IBA) methods at the accelerator could serve as an  analytical basis for development of practical approaches for the every-day A reliable, simple identification method is needed by conservators to identify the metal tannate inks in order to perform adequate treatments.

A simple, non-bleeding iron(II) test has been developed as a rapid method to detect iron(II) ions in cellulose. The test strips containing indicator bathophenantroline are non-bleeding and can therefore be used on originals. On contact with iron(II) ions, a red colour of the strip develops. Although promising, the test had not been published and no tests on the reliability of the method have been performed so far. Only about 45% of iron in iron gall inks was found to be in the form of iron(II) ions, which are detected with the indicator. Furthermore, the solubility of several ferrous compounds in water is quite low, further decreasing the concentration of ferrous ions detected by wet indicator strips. Also, the red colour is sometimes hard to distinguish from the brown degradation products. This is even more problematic in case copper is present in the ink, as it may form yellow-green complexes with the indicator. A verification of the reliability of the test is clearly needed, as well as possible development of additional ones, based on identification of ferrous and ferric ions or peroxides.