Contribution-MIP2006

							        Metals in paper - MIP - EU Thematic Network EVK4-2002-20010
        Final Conference - Newcastle Upon Tyne, UK, 24-27 January 2006

                              Surface roughness of degraded paper
                      G. Piantanida1,2, M. Bicchieri2 , F. Pinzari2 and C. Coluzza1
                      1
                     Università degli Studi di Roma "La Sapienza" - Dipartimento di Fisica
                                     P.le Aldo Moro, 2 00185 Roma. ITALY
                         TELEPHONE: (+39)-06-49913958 FAX: (+39)-06-4463158
        email: Giovanna.Piantanida@roma1.infn.it web: http://nanolabserver.phys.uniroma1.it/open.html
                                  2
                                    Istituto Centrale per la Patologia del Libro.
                                      Via Milano, 76. 00184 Roma. ITALY.
                                        email: icplch@tin.it ; icplbio@tin.it


    Summary: This work reports the application of Atomic Force Microscopy (AFM) in detection of paper
    ageing-markers: aside from topographies, surface roughness parameter ( ) was evaluated. Samples non-
    treated and oxidized were investigated as well as original ancient documents, showing foxing stains.
    The considered processes are the chemical reactions induced by an accelerated ageing in climatic
    chamber (80°C, R.H. 65%), by oxidation with a KIO4 0.015M water solution and subsequent ageing, and
    the effects of a fungal attack reproduced in vitro inoculating paper samples with Aspergillus terreus Thom
    (6000spores/100l, 27°C, R.H. 100%). Comparison between  values along artificial treatments and
    values related to naturally degraded samples provides evidence of complexity in the natural process.

    Keywords: AFM, paper, cellulose, degradation

1     Introduction                                           immersions, 5 minutes each, in distilled water. Both
                                                             oxidized and untreated samples were subjected to a
Atomic Force Microscopy (AFM) can be used to                 temperature and moisture-stimulated accelerated
study cellulose fibres degradation directly on paper         ageing in a climatic chamber, in air environment,
surface, and it can provide both qualitative and             at 80°C and 65% RH, according to International
semi-quantitative information on their deterioration         Organization for Standardization (ISO) 5630-
and ageing. The technique can produce                        3/1996 standard. Aspergillus terreus Thom
topographical maps of paper consisting of three-             (ATCC10690), a fungal strain frequently associated
dimensional images of the surface ultra structure at         with library material bio-deterioration, was
molecular level, in real time, under atmospheric             inoculated on a further paper samples series. The
conditions, and without the need for fixation of             inoculum was performed with spore suspension in
samples. Surface hydrophobic properties, surface             nutritive broth (Sabouraud Broth, DIFCO, Becton
charges, and mechanical properties can be                    Dickinson, USA) with a method described in
investigated with AFM that, therefore, can provide           previous papers [1], [2].
a new insight into the relationships between
                                                             2.2 Atomic Force Micoscopy
spoiling organisms and substrata surfaces. In this
study, AFM technique has been used to observe the            For surface roughness measurements, we used a
degradation of cellulose fibres in paper samples             SNOM/AFM instrument assembled at ISM-CNR,
used as substrata for the growth of a filamentous            operating on air, mounting a quartz fibre probe with
fungus known to be responsible for damages on                conical tip (diameter30nm). In order to outline a
objects of art made from or supported on paper.              reproducible method, a non-contact operating mode
Images obtained from the analysis of artificially            was preferred to a contact mode so as to avoid the
deteriorated samples has been used for a                     possibility of surface damage occurring, which is
comparison with topographies obtained by AFM                 experienced with non-coated papers and other soft
from naturally affected samples. As “control”                materials. Eventually, surface morphologies of
images, AFM topographies of samples obtained                 ancient library papers showing foxing stains were
from the same paper quality utilised as substrata for        measured, in order to compare roughness of the
fungal inoculum were considered.                             stain areas with that of other parts of the sheet.
2     Materials and Methods                                  3    Results and Discussion
2.1 Samples preparation                                      AFM imaging provided qualitative indication of
The investigated material was pure cotton Whatman            surface deterioration induced by both chemical and
N.1 chromatography, ash-free paper. Some samples             biological oxidation. The variations can be
were oxidised by immersion for 15 minutes in a               quantified through surface roughness parameter.
KIO4 0.015M water solution, at pH=5.0 by addition            Local surface roughness is defined, on each
of 0.1M hydrochloric acid, and then rinsed by two            10mx10m frame, as the root mean square
deviation of the surface height from its average         structure, that result in a value quite different from
value, i.e. roughness of the single image.               the paper value.
For each sample, 10 different areas were imaged;
sample surface roughness is here intended as the
average, over all measured areas of the same
sample, of the local roughness values.




Fig. 1. Whatman N.1 samples: a) untreated; b) inoculed
with Aspergillus terreus; c) oxidised with KIO4; d)
artificially aged; e) oxidised and artificially aged.
Fig.1 shows that surface roughness parameter
allows a significant discrimination between control      Fig. 3. AFM imaging of Letter from Innocenzo Coreti:
                                                         paper and stain
samples and in vitro deteriorated samples, even
though it was not possible to distinguish between        Standard errors of roughness data can be considered
the degraded samples, both oxidised and                  themselves somehow informative: in fact, while a
biologically spoiled .                                   diffuse deterioration, like artificial ageing does not
                                                         affect data deviation from average value, natural
                                                         processes such as spontaneous ageing and single
                                                         stains can bring to higher variability of the error
                                                         (Fig. 2).
                                                         Surface roughness analysis provide, therefore, a
                                                         quantitative parameter useful in the evaluation of
                                                         the paper surface condition. The analysis is being
                                                         integrated [3] with surface height statistics and
                                                         power spectrum analysis in order to better test the
                                                         suitability of Atomic Force Microscopy in paper
                                                         diagnostic.
                                                         References
                                                         [1] O. Canhoto, F. Pinzari, C. Fanelli, N. Magan .
                                                         Application of electronic nose technology for the
Fig. 2. Original samples : a) Letter from Innocenzo
Coreti - biologically damaged; b) De Officio e(t)        detection of fungal contamination in library paper.
Potestate Episcopi – chemically damaged.                 International Biodeterioration & Biodegradation.
                                                         54 (2004) 303–309.
On naturally aged library samples, roughness             [2] G. Piantanida, M. Bicchieri, F. Pinzari and C.
analysis cannot be related to the degradation state      Coluzza. Atomic force microscopy imaging directly
of the paper because no undamaged samples are            on paper: a study of library materials degradation.
available as a reference. An application for the         In: R. Salimbeni and L. Pezzati, eds. Proc. of SPIE
same method can be found, instead, in the                V. 5857: Optical Methods for Art and Archaelogy.,
comparison between foxing stains and paper               pp. 217-227, Munich, Germany, 13-16 June 2005.
(Fig.2). Data reflect the qualitative observations       SPIE.
already achieved on the AFM topographies (Fig.3)         [3] G. Piantanida, M. Bicchieri and C. Coluzza.
[2]. On the biologically damaged sample, the stain       Atomic Force Microscopy study of surface
morphology cannot be distinguished from paper            morphologies in degraded paper. Polymer. V.46
morphology. Contrariwise, stains on the chemically       N.26 (2005) 12313-12321.
damaged sample show typical feature of repeated