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To treat or not to treat? The complex case of corrosion of iron gall ink

The conservation of historical documents and archives is extremely important for the preservation of the history and culture of a society. Unfortunately, Iron gall ink corrosionl is a common problem with old documents and can cause irreparable damage if not treated properly.


Iron gall ink is an ink that contains iron in its composition and is widely used on old documents, especially books, letters and maps produced between the 18th century and the mid-20th century. The main constituent elements of the ink are: water (H2O), wine or vinegar (additives), gum arabic (binder), gall (scientific name) and iron sulphate (FeS 2+), the latter being the main element responsible for the paper. degradation (Gomes et al).




Unfortunately, this ink is susceptible to corrosion, which is caused by oxidation of the iron in its composition. When this happens, the ink begins to deteriorate, creating yellow spots and holes in the paper.


According to Gomes et al, the degradation process can be identified in 3 stages:


1st Phase: Fluorescence

2nd Phase: Brownish discoloration

Stage 3: Paper Collapse



Verónica et al. Estudio a temperatura ambiente de la degradación del papel impregnado de tinta de hiel de hierro bajo diversas condiciones de oxígeno y humedad: monitoreo dependiente del tiempo mediante mediciones de espectrometría de borde cercano de absorción de rayos X y viscosidad. Marzo de 2011 Química analítica 83(7):2589-97.


To preserve documents degraded by iron gall ink corrosion, it is necessary to take some specific measures. The first step is to identify the degree of deterioration of the document, for which it is important to have the help of a professional specialized in conservation and restoration of documents. Based on this evaluation, it is possible to determine the best approach to preserve the document.


One of the most common techniques for preserving documents degraded by iron gall ink corrosion is chemical treatment. This method involves the application of chemicals that neutralize the acids produced by the oxidation of the Iron Gall Ink and help stabilize the deterioration. In 1995, the Dutch chemist Johann Neevel developed the treatment in an aqueous medium known as calcium phytate, which combats these two mechanisms of deterioration and has an effective action in stabilizing manuscripts with iron gall ink. Calcium bicarbonate and phytic acid-based treatments are also being tested to stabilize this type of damage.


It is important that this treatment is done carefully, as excessive use of chemicals can further damage the document.


Another technique used to preserve documents damaged by the corrosion of iron gall ink is encapsulation. This technique consists of using a transparent plastic film to cover the document, protecting it from humidity and other factors that could aggravate its deterioration. However, this technique is controversial, as some experts argue that encapsulation can speed up the deterioration process, making it more difficult to recover documents in the future.


Maintaining relative humidity below 60% and handling with care are the most effective strategies for extending the life of originals made with iron gall ink. If interventional treatment cannot be avoided, the aqueous phytate method is recommended. A non-aqueous treatment specifically designed for paint-corroded artifacts is not yet on the market. But be careful: all intervention measures introduce new risks that can be dramatic in the long run!


https://irongallink.org/conservation-ink-corrosion-para-tratar-o-no-tratar.html


In conclusion, the conservation of documents degraded by the corrosion of iron gall ink is a challenge for professionals in the conservation and restoration of documents. It is important that documents are treated with care and that the techniques used are chosen based on a detailed assessment of the state of deterioration of the document. With the necessary care, it is possible to preserve the history and culture of a society for many years.


➡ Do you want to know more about this topic?

We have a new course waiting for you here!


See details of the course with Prof. Thiago Guimarães on Basic Chemistry for restorers and conservators [In portuguese]




And the course of Conservation of Books and Documents with Profa. Fernanda Auada [In Portuguese]




Referencias:

Conservación de tintas con hiel de hierro. Disponible en: https://www.adrientaunay.org.br/portugues/digitalizacao-e-restauro/conservacao-das-tintas-ferrogalicas

Gomes et al. Conservación de Documentos Degradados por Corrosión de Pintura Ferrogalica https://abm.madeira.gov.pt/wp-content/uploads/2020/04/artigo-tinta-ferrog%C3%A1lica.pdf

Verónica et al. Estudio a temperatura ambiente de la degradación del papel impregnado de tinta de hiel de hierro bajo diversas condiciones de oxígeno y humedad: monitoreo dependiente del tiempo mediante mediciones de espectrometría de borde cercano de absorción de rayos X y viscosidad. Marzo de 2011 Química analítica 83(7):2589-97.



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