It is used by conservators to test manuscripts and documents without damaging them because it is non-bleeding.
Developed by the Conservation Research Department at the Netherlands Institute for Cultural Heritage (ICN). Gall-10rar
The test paper is moistened and applied to the ink. If iron (II) ions are present, the test paper changes color (turns a red/purple complex) due to the indicator bathophenanthroline reacting with the iron. It is used by conservators to test manuscripts