Elsevier

Journal of Cultural Heritage

Volume 18, March–April 2016, Pages 250-257
Journal of Cultural Heritage

Original article
Calcium hydroxide nanoparticles in hydroalcoholic gelatin solutions (GeolNan) for the deacidification and strengthening of papers containing iron gall ink

https://doi.org/10.1016/j.culher.2015.10.005Get rights and content

Abstract

A severe decay process, catalyzed by acidity and metal ions, affects cellulose in historical manuscripts and books that contain iron gall inks. The inhibition of this process can be achieved by alkaline-earth nanoparticles dispersions in alcohols, which create a neutral environment in which both oxidation and depolymerization of cellulose are hindered. As a result of the degradation process, paper in historical manuscripts and books is fragile and very difficult to handle. A reinforcement intervention with gelatin and Japanese tissue could be used for the strengthening of historical manuscripts, even if this method could not prevent paper degradation due to iron gall inks. Therefore, a new method, combining a deacidification treatment based on calcium hydroxide nanoparticles and a reinforcement process using Japanese tissue has been developed and tested on mockups containing iron gall inks. The protective action arising from the combined treatment was evaluated by performing cellulose viscosimetric degree of polymerization (DPv) and pH measurements on artificially aged systems. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) was used for the evaluation of calcium distribution from the deacidification agent within samples cross section. Determinations of DPv clearly showed that the degradation of untreated inked paper was significantly slowed down by the combined treatment. The method was also tested on original manuscripts from 16th and 18th century. SEM-EDX maps showed that the applied treatment, which raised the pH to an appropriate value, is homogenously distributed over the treated surfaces.

Section snippets

Research aims

Cellulose in historical manuscripts is subjected to several decay processes that may lead to irreversible degradation and to the ultimate loss of valuable information. The presence of metal or iron gall inks in manuscripts is responsible for cellulose corrosion due to the synergistic action of acid-catalyzed hydrolysis and metal-catalyzed oxidation. It has been recently demonstrated that alkaline-earth nanoparticles dispersions in alcohols neutralize manuscripts acidity, raising the pH and

Chemicals

Arabic gum, and gall nuts were provided by Zecchi, Art Shop in Florence. Iron(II) sulfate heptahydrate (Ph. Eur.; chlorides < 300 ppm, Zn < 500 ppm, heavy metals < 50 ppm, Fe(III) < 0.5%, Mn < 0.1%) was supplied by Fluka Chemicals, as well as the other reagents for the preparation of iron gall ink, i.e., ethyl alcohol (99.8%) and acetic acid (99.5%). Type B gelatin, extracted in alkaline environment from bovine skin and connective tissues, was supplied by Helm Iberica. Ethanol absolute (99.8%, Fluka), n

Results and discussion

Calcium and magnesium hydroxide nanoparticles dispersed in short-chain alcohols were proposed as deacidifying agents for paper about 15 years ago [10], [11], [12] and their efficiency was assessed in several studies [13], [14], [26], [31], [32], [33], [34]. Stable and highly concentrated nanoparticles dispersions in ethanol and n-propanol have been recently obtained by a solvothermal reaction [26]. These dispersions were used for developing the GeolNan method, a restoration procedure for the

Conclusions

A new method, combining a deacidification treatment based on calcium hydroxide nanoparticles and a reinforcement process with gelatin and Japanese tissue, has been proposed for the conservation of paper containing iron gall inks. The treatment, which can be prepared in water and ethanol or water and n-propanol, was applied by brushing on inked mockups, which were artificially aged at high temperature and relative humidity.

Significant differences in cellulose viscosimetric degree of

Acknowledgments

The authors would like to thank Luisa Aroldi for her collaboration during the experimental tests on paper. This work was partly supported by CSGI, and by the European Union, Project NANOFORART (FP7-ENV-NMP-2011/282816).

The work developed at the University of Barcelona and at the Archive of the Crown of Aragon was funded by the Ministry of Science and Innovation in two consecutive projects named HAR-2011-29654 and HAR-2014-56526.

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