Conservation of Cultural Heritage
Topic 1:
Salt crystallization in po materials
Topic 2:
Application of Magnetic Resonance Imaging (MRI) in the study of porous materials
Topic 3:
New methods for wall paintings consolidation based on i nnovative nanotechnologles
Topic 4:
Nanotechnology for paper's deacidlfl cation
Topic 5:
Cleaning techniques for frescoes: solubilization of hydrophobic materials by means of microemulsions and gels
Current projects
NANOTECHNOLOGY FOR PAPER DEACIDIFICATION: BASIC DISPERSIONS
THEIR PREPARATION AND USE IN PROCESSES FOR PAPER DEACIDIFICATION
Research Unit(s)
CSGI unit - University of Florence
People Involved
Dr. Rodorico Giorgi
Dr. Claudius Vinicius schettino
Prof. Luigi Dei
Prof. Piero Baglioni
It is well known how the presence of acidity in paper is the main responsible of its degradation with consequent loss of a lot of important information and in particular of historically important documents. The acidity, which is present particularly in modern paper, forms during the paper manufacture, it is also a consequence of the use of acid inks (which are very common especially in the last centuries) or because of the adsorption of acid pollutants which are present in the air.
Many different techniques and products have been studied or developed in order to eliminate acidity from paper and published documents (paper de-acidification). Unfortunately, up to now the problem is far to be satisfactorily solved, and the specialists are intensively looking for new products capable of annulling the acidity present in paper. Calcium, magnesium, and barium hydroxide aqueous solutions have been widely used for many decades, but, unfortunately, they had often induced not desirable side effects, because of their strong alkaline conditions, with subsequent depolymerization of cellulose.
Scientific Background
Non aqueous deacidification processes have also been proposed. In Smith R.D., Mass
Deacidification at the Public Archives of Canada in Conservation of Library and Archive Materials and the Graphic Arts, Butterworth Ed., London, 1987 the use of magnesium alkoxide deacidification solutions (Wei TÍo method) is described; another method widely used is the
Bookkeeper method which is based on the application of suspended MgO that, subsequently

converted in magnesium hydroxide, forms the alkaline reservoir. Unfortunately, these methods use chlorofluorocarbon (CFC) solvents. Alternatively, some solvent mixtures have been recently experimented, as thrielyne (90%) and methanol, but all of them are harmful.
Despite of its scarce usage, calcium hydroxide is an excellent deacidifying agent. Calcium hydroxide is physico-chemicaliy friendly to most of papers and, once converted to calcium carbonate, works efficiently as alkaline reservoir.
In IT 1.286.868 (Patent) it is reported that suspensions of calcium hydroxide could be used to consolidate mural paintings and to deacidify paper. However, the calcium hydroxide suspensions in organic solvent were obtained from lime and the particle size distribution was quite broad and larger than several micrometers. Smaller particles were around 0.5 microns, 80% were greater than
1 micron. This originated two problems: firstly, kinetic stability was good but not excellent for some application procedures, for example spraying; secondly, because of particle sizes, a white glaze (or spots) on the treated surfaces could form. Large calcium hydroxide particles showed a poor adhesions and penetrability into the cellulosic fibres. Deacidifying agents must ensure good adhesion with fibres, so that the alkaline reservoir acts efficiently. Therefore, according to physicochemical features of cellulose, particles with a surface charge density are preferred. Both these requirements are ensured by the use of particles smaller than micron size.
Main Findings
Many different techniques and products have been studied or developed in order to eliminate acidity from paper. Unfortunately, up to now the problem is far to be satisfactorily solved, and the specialists are looking for new products capable of annulling the acidity present in paper. Calcium, magnesium, and barium hydroxide aqueous solutions have been widely used for many decades, but, unfortunately, they had often induced not desirable side effects, because of their strong alkaline conditions, which promotes cellulose depolymerization. Several non-aqueous deacidification processes have also been proposed. Even though appreciable results are obtained, some disadvantages are longer to be overcome, specially concerning the used solvents, which are environmentally unfriendly. Despite its scarce usage, calcium hydroxide is an excellent deacidifying agent. Calcium hydroxide is physico-chemicaliy friendly to paper and, once converted to calcium carbonate, works efficiently as alkaline reservoir. Calcium hydroxide nanoparticles dispersed in alcohol offer an innovative solution for paper deacidification. The used solvents are environmentally friendly. Moreover, as non-aqueous dispersion, it could be applied by different techniques, as brushing or spraying (see the picture), providing excellent results.
PUBLICATIONS
Patents o Baglioni, P., Dei, L, Giorgi, R., Schettino, C.V., Basic suspensions: their preparation and use in processes for paper deacidification, International patent pending, PCT/EP02/00319, Jan 15, 2002.
o Baglioni, P., E. Carretti e L Dei, Microemulsioni ed Emulsioni di Olio in Acqua, loro Uso per la
Solubilizzazione di Resine Polimeriche e Impacchi Contenenti dette Microemulsioni ed Emulsioni,
Brevetto Italiano n. FI/99/A/000071, 2 Aprile 1999.
o Baglioni, P., L. Dei, E. Ferroni e R. Giorgi, Sospensioni Stabili di Idrossido di Calcio, Brevetto
Italiano n. FI/96/A/000255, 31 Ottobre 1996.
o Ferroni, E., G. Gabrielli and G. Caminati, Oil-in-Water Microemulsions to remove Hydrophobic
Materials from Pictorial Surfaces, European Patent EP 91105096, 1991.
o Ferroni, E. and P. Baglioni, Autogeneously Air Setting Mortars, European Patent EP 411583,
Feb 6, 1991.

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o Ambrosi, P. Baglioni, P. R. David, L. Dei, R. Giorgi, C. La Mi, A. Mairani, M. Matteini, M.
Rizzi, G. Schonhaut and G. Lanterna, Inorganic Consolidants and Protectives for Architectonic
Surfaces: Experimental Tests on Santa Prisca Church Apse in Rome, Proceedings of the 2nd
International Congress for the Safeguard of the Cultural Heritage in the Mediterranean Basin, Paris,
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Solubilise Hydrophobic Materials, in Proceedings of the 5th World Surfactants Congress - Cesio
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;
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(1999) 92. o Dei, L, P. Baglioni and M. Mauro, Materials for Wall Paintings Conservation: Changes of
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Properties and Aging Effects, in Proceedings of the 6th International Conference on "Non
Destructive Testing and Microanalysis for the Diagnostics and Conservation of Cultural and
Environmental Heritage, Art '99", Rome, May 17 - 20, 1999, pp. 543-554. o Dei, L., P. Baglioni, G. Bitossi and M. Mauro, Thermal Analysis in the Characterisation of Salt
Efflorescences in Cultural Heritage Conservation, in Proceedings of the 6th International
Conference on "Non Destructive Testing and Microanalysis for the Diagnostics and Conservation of Cultural and Environmental Heritage, Art '99", Rome, May 17 - 20, 1999, pp. 531-542. o Dei, L, P. Baglioni, E. Ferroni, A. Ahle, A. M. Maetzke A. Parronchi and M. Spampinato,
Mediaeval Polychrome Sculptures in Arezzo: History and Painting Technique, Preprints of the 17th
IIC Congress, Poster Session, Dublin, 6-11 September 1998, IIC Publishers, London, 1998, 3. o Dei, L., M. Mauro and G. Bitossi, Characterisation of Salt Efflorescences in Cultural Heritage
Conservation by Thermal Analysis, Thermochimica Acta, 317 (1998) 133. o Dei, L., A. Ahle, P. Baglioni, D. Dini and E. Ferroni, Wall Paintings Conservation and Green
Degradation Products of Azzurite, Studies in Conservation, 43 (1998) 80. o Mauro, M., G. G. T. Guarini and L. Dei, A Thermal Method for Quantitative Determination of
Potassium Nitrate in Wall Paintings, Science and Technology for Cultural Heritage, Giardini
Editoři, Pisa, 6(1), 1997, 35. o Baglioni, P., L. Dei, F. Pique', G. Sarti and E. Ferroni, New Autogenous Lime-Based Grouts used in the Conservation of Lime-Based Wall Paintings, Studies in Conservation, 42, 1997, 43. o Baglioni, P., L. Dei and E. Ferroni, La Priorita' delle Competenze Chimiche per la Comprensione dei Manoscritti Alchemici, Critica d'Arte, VII série, Anno LIX, 6 (1996) 41. o Dei, L., P. Baglioni, G. Sarti and E. Ferroni, Aging Effects on Ammonium Carbonate/Acetone
Solutions and Cleaning of Works of Art, Studies in Conservation, 41 (1996) 9. o Borgioli, L., G. Caminati, G. Gabrielli, and P. Baglioni, P., Removal of Hydrophobic Impurities from Pictorial Surfces by means of Heterogeneous Systems, Science and Technology for Cultural
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Fine '400. Affreschi Restaurati di Antonio da Fabriano in San Domenico, Arti Grafiche Gentile,
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Conservation Institute, Marina del Rey, July 1993.
o Dei, L. e G. Sarti, I Pigmenti Azzurri della Veste della Madonna del Parto a Monterchi, in "II
Restauro della Madonna del Parto a Monterchi", Marsilio Editore, Venezia, 1993, pp. 86-87. o Pique', F., L. Dei and E. Ferroni, Physicochemical Aspects of the Deliquescence of Calcium
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Selected Prof. Ferroni's publications o Ferroni, E., Riflessioni sui Processi Degradativi dell'Intonaco e sui Metodi di Intervento, Atti del
Convegno Internazionale di Studi 'Piero della Francesca ad Arezzo', Arezzo, 7-10 Marzo 1990,
Marsilio Editore, Venezia, 1991, pp. 219-231. o Ferroni, E., Contributi e Prospettive della Ricerca Chimico Fisica nel Restauro degli Affreschi,
Atti e Memorie dell'Accademia Petrarca di Lettere, Arti e Scienze di Arezzo, Vol. XL Nuova Serie,
Anni 1970-1972, pp. 169-179. o Ferroni, E. and D. Dini, Esperienze sul Sequestro di Nitrati con Tributilfosfato per il Distacco e la
Conservazione degli Affreschi, Atti della XLI Riunione della SIPS Societa
1
Italiana per il Progresso delle Scienze, Siena, 23-27 Settembre 1967, Vol. 2, SIPS Ed., Roma, 1968, pp. 919-932. o Ferroni, E., V. Malaguzzi-Valerj and G. Rovida, Experimental Study by Diffraction of
Heterogeneous Systems as a Preliminary to the Proposal of a Technique for the Restoration of
Gypsum Polluted Murals, Proceedings of the ICOM Conference, Amsterdam, September 1969. o Ferroni, E., V. Malaguzzi-Valerj and G. Rovida, Utilisation de Techniques Diffractometriques dans I'Etude de la Conservation des Fresques, Actes de l'8em Colloque sur I'Analyse de la Matiere,
Florence, 15-19 Septembre 1969.