This non-bleeding iron test paper has been developed by the Conservation Research Department at the Netherlands Institute for Cultural Heritage/ Instituut Collectie Nederland as a simple and quick method to detect iron (II) ions in hydrophilic substrates. Iron ions are harmful to organic substrates like paper, because they catalyse the oxidative degradation of cellulose and other organic materials. The test paper is non-bleeding, so it can be applied to originals. Iron-Gall Ink Testing Paper has been extensively tested in paper conservation. In general a positive reaction of the iron (II) test is a distinct identification of the presence of an iron-gall ink. However, it has to be realised that other inks and colourants, eg bistre, may be iron-based or contaminated with iron.
Iron (II) ions are water-soluble and will migrate into a dampened test paper in contact with the ink. The indicator (bathophenanthroline) forms an intensely red-coloured complex with irons (II) ions. Instructions are provided with the test papers.