Aqueous treatment - All-or-non law
Birgit Reissland, Karin Scheper and Sabine Fleischer (2007)
For unique items like manuscripts and drawings written or drawn with iron gall inks, risks and benefits of any treatment action should be thoroughly compared in order to make an informed decision. We are explicit on the fact that after an aqueous and non-aqueous treatment, most information that is inherent in the artefacts material is irreparably lost. Be aware that such treatments completely change both the ink and paper composition. Analysis of ink and paper composition that provides scientific data for dating, provenience, authorship or other comparable questions can not be carried out after such treatments anymore since it generates incorrect results. Therefore, a decision for preventive measures, local treatment and minimal intervention should always be a preferred alternative to any aqueous or non-aqueous treatment of an entire artefact!
The general rule for any aqueous treatment of iron-gall inks on paper is the following: Either do not apply any aqueous treatment at all, or apply the entire treatment. Treating “just a bit” bears the highest risk.
> Never humidify: The highest risk for objects with iron-gall ink on paper is to introduce moisture by increasing the humidity. This can happen just during storage or transport (tropical conditions, salt mines) but also deliberately by humidifying objects for e.g. subsequent flattening (Gore tex®, humidity chamber). Increased moisture content facilitates migration of water-soluble compounds out of ink lines into the surrounding paper. Since some of the most detrimental compounds are not visible (iron(II) ions, sulphuric acid) this process is often not noticed but the risk of activation of degradation reactions like hydrolysis and oxidation especially on the long term is increased significantly. Therefore, NEVER humidify iron-gall inks on paper without subsequent application of a thorough aqueous treatment procedure that allows removal of soluble detrimental compounds.
> Wash thoroughly: It is essential to remove all water soluble compounds in so far as possible. Most effective for this purpose are immersion and suction table treatments.
> Alcohol is not safe: Always consider that certain ink ingredients like Gallic acid or particular dyes are soluble in alcohol and other polar solvents. Thus working with ethanol or iso-propanol does NOT prevent migration of those soluble compounds and also bears the risk of immediate or long-term discolouration if those ions were not removed beforehand.
> Mendig with aqueous adhesives is a risk: When water-soluble adhesives are applied it is obvious that water is introduced into the system. Soluble compunds like iron(II) ions and sulphuric acid immediately migrate out of ink areas into surrounding paper. The result is a degradation of those areas and becomes visible as brown discolouration around ink areas after ca. 25 years. Limiting the amount of water to a minimum is therefore crucial (Jacobi et al in print).
> Never bleach oxidatively: Applying oxidative bleach on objects that contain transition-metal ions (like iron-gall inks, iron inclusions or copper-containing pigments) is extremely detrimental since the paper areas that contain transition metals will severely degrade and discolour to brown in just a few (3-6) months. Therefore NEVER apply any oxidative bleach on objects with iron gall ink.