10.6092/issn.1973-9494/7124
Il presente studio propone l’analisi e l’approfondimento di un materiale già noto nel campo del restauro: la polpa di cellulosa, utilizzata da sempre come supportante per impacchi di pulitura su materiale lapideo, qui analizzata in veste di stucco per supporti lignei. Il materiale è stato utilizzato in alcuni interventi di restauro eseguiti nel laboratorio del Museo Diocesano di Palermo nel corso degli ultimi 10 anni su sculture lignee e dipinti su tavola. Le opere conservate in sale espositive costantemente monitorate hanno permesso, fino ad oggi, di valutare l’efficacia dell’intervento. Lo studio propone alcuni test eseguiti su campioni di stucco di cellulosa realizzati con leganti di origine diversa, valutando le caratteristiche di ciascuna tipologia, i tempi di essiccamento, ritiro, perdita in peso, affinità al colore, etc. Inoltre sono stati effettuati test d’invecchiamento, reversibilità e test microbiologici per determinare la resa della cellulosa all’invecchiamento e valutare se il substrato in cellulosa possa costituire un supporto alla colonizzazione microbica.
application/pdf
1973-9494
7124
2
en
Bartolomeo Megna
Conservation Science in Cultural Heritage
bio-receptivity
New Applications in the Use of Cellulose Pulp for the Integration of Wooden Supports
Text.Serial.Journal
https://conservation-science.unibo.it/
15
Articles
2017-06-01
2017-07-04
2017-06-01
2017-09-04
121-133
CSCH
Bartolomeo Megna
2015
10.6092/issn.1973-9494/7124
121
Università degli Studi di Palermo
1973-9494
2
bio-receptivity
en
133
New Applications in the Use of Cellulose Pulp for the Integration of Wooden Supports
https://conservation-science.unibo.it/article/download/7124/6834
15
N     EW APPLICATIONS IN THE USE OF CELLULOSE PULP
      FOR THE INTEGRATION OF WOODEN SUPPORTS

    Fulvia Bartolone
    Professional freelance restoration, Palermo, Italy
    Mauro Sebastianelli
    Arcidiocesi di Palermo, Via Matteo Bonello 2, Palermo, Italy
    Enza Di Carlo, Giovanna Barresi, Franco Palla*10
    Laboratorio Biologia e Biotecnologie per i Beni Culturali, Università degli Studi di
    Palermo, Dipartimento STEBICEF, Via Archirafi 38, Palermo, Italy
    Bartolomeo Megna
    Laboratory of Materials for Restoration and Conservation, Dipartimento di Ingeg-
    neria Civile, Ambientale, Aerospaziale, dei Materiali, Università di Palermo, Italy

    Keywords: wood artifacts; reintegration; binders; bio-receptivity


    1. Introduction

   The plastic reintegration of historical-artistic wooden artworks in the field of resto-
ration has been somewhat neglected by scientific research and mostly relegated to
the sector of traditional handicrafts. In the course of time, restorers have used a wide
range of traditional products, such as chalk and rabbit glue, wax, and other more com-
mon synthetic materials. However, these materials have not always been appositely
designed for the restoration of wooden artworks. The listed materials have also often




                                                                                                         CONSERVATION SCIENCE IN CULTURAL HERITAGE
been mixed together in an arbitrary way, without taking into account whether they were
compatible with the wooden structure and to what degree. So far, few attempts have
been made to identify new and more appropriate materials that might be used for this
purpose [1, 2]. Modern materials for wood restoration have quite good characteristics
(easily applicable, speed of drying, good workability), but these positive aspects often
overshadow the compatibility of the products with the wood.
   The present study shows, also in terms of materials compatibility, several products
that are the most suited for wood restoration, as well as demonstraing the potential use
of cellulose pulp as being well-suited for the restoration of wooden artifacts also from a
chemical point of view, as it is the main component of wood (Figure 1).
   Cellulose pulp is a material that is already used in the field of restoration for other pur-
poses and here it is suggested in a new role as a stucco for wood, mixed with different adhe-
sives selected from the wide range of present-day products [3]. By analysing the cellulose
pulp it was possible to investigate this material in-depth and evaluate its original properties,
as well as consider the susceptibility of cellulose material to microbial colonization.
   Moreover, the samples of cellulose pulp underwent artificial aging and solubility and
reversibility tests using known polarity solvents in order to evaluate the potential use
of cellulose pulp as a stucco in the reintegration of wooden artifacts, as an alternative
to materials utilized today.


*   Corresponding author: franco.palla@unipa.it

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F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                    Figure 1. a) Different steps in gap-filling on a papier-mache crucifix (16th century) stored in
                                                                                                                                    the Diocesan Museum in Palermo. Detail of the Christ’s heel before restoration (on the left);
                                                                                                                                    reintegration with pigmented cellulose pulp+acrylic resin (center); refining in gypsum+ rabbit glue
                                                                                                                                    (on the right); b) Crucifix (verso).



                                                                                                                                       2. Materials and methods

                                                                                                                                        In order to give the cellulose pulp-based stucco good filler properties, research was
                                                                                                                                    carried out on adhesives with fairly good elasticity, malleability and ease of prepara-
                                                                                                                                    tion, minimal water intake and that were also lightweight, fast drying, and strong [4].
                                                                                                                                        Considering these specific aspects, we assayed three adhesives based on: i) pro-
                                                                                                                                    teins (rabbit glue); ii) cellulose ethers (Klucel-G, Tylose MH300P); iii) synthetic poly-
                                                                                                                                    mers (BEVA-D8S, PLEXTOL-B500, AQUAZOL 200).
                                                                                                                                        Attention then focused on the materials made of cellulose ethers because, up to
                                                                                                                                    now, they have been considered the most suitable in terms of non-toxicity, reversibility
                                                                                                                                    and biodegradability, although they have not yet been scientifically tested as adhesives
                                                                                                                                    for fillers. The adhesives assayed in this work are listed below:
                                                                                                                                        – RABBIT GLUE: a water-soluble animal glue, characterized by high adhesive pow-
                                                                                                                                    er, created by prolonged boiling of animal connective tissue. The glue was assayed at
                                                                                                                                    different concentrations (1:5; 1:7; 1:10; 1:14). In particular, the concentration equal to
                                                                                                                                    1:14 was considered the most appropriate to use, because the dough was more flex-
                                                                                                                                    ible during the drying step. However, its excessive water content can limit its applica-
                                                                                                                                    tion in wooden artifacts.
                                                                                                                                        – TYLOSE MH300 P: hydroxyl-methylcellulose is a synthetic polymer. Its adhesive
                                                                                                                                    power is very low, it is thus, easily reversible. Generally, Tylose solutions are utilized
                                                                                                                                    for paper restoration as 1-2.5%. For the stucco preparation Tylose MH300P was used
                                                                                                                                    at 5% in H2O or at 5% in H2O/EtOH (1:1).
                                                                                                                                        – KLUCEL G: hydroxyl-propylcellulose has high surfactant properties. It is utilized
                                                                                                                                    as a fixative in mural paintings or in paper restoration at low concentrations. For the
                                                                                                                                    stucco preparation, it was used at 5% in H2O or at 5% in H2O/EtOH (1:1).
                                                                                                                                        – AQUAZOL 200: thermoplastic polymer is made of two poles (2-ethyl-2-oxazoline).
                                                                                                                                    It is used as a consolidating agent in paint layers; it is soluble in water and in high /
                                                                                                                                    medium polarity-solvents. It is biodegradable and has good thermal stability and low
                                                                                                                                    toxicity. In this study, Aquazol 200 was utilized at 25% in EtOH.
                                                                                                                                        – PLEXTOL B500: thermoplastic acrylic resin, with good viscosity in aqueous dis-
                                                                                                                                    persion. Acrylate and methacrylate copolymer with good chemical resistance. It is uti-
                                                                                                                                    lized for relining paintings and for re-adhesion of paint layers. In this study, it was
                                                                                                                                    utilized pure to obtain a very structural filler stucco.


                                                                                                                              122
   - BEVA D8S: consists of an ethylene vinyl acetate emulsified by polyvinyl-alcohol. It
is utilized mainly for canvas waterproofing. In this study it was utilized pure to obtain a
very structural filler stucco.
   All stuccos were prepared maintaining the ratio of adhesive / cellulose powder (4 ml
of adhesive/1 g of cellulose) constant. Several samples were designed for each type
of stucco in order to carry out the analysis below:
   1. Weight loss (%): to evaluate effective stucco weight
   2. Shrinkage: analysis of sample, dimensions decrease during drying (Figure 2)
   3. Artificial aging
   4. Reversibility test: to evaluate the removal of material, both mechanically or us-
         ing solvents with increased polarity
   5. Microbiological susceptibility: to determine the microbial susceptibility of cellulose.




Figure 2. a) wet sample; b) cellulose pulp + Aquazol 200 dry sample, without shrinkage during
drying; c) cellulose pulp + rabbit glue with shrinkage during the drying.

   2.1 Shrinkage and weight loss in percentage

    For each adhesive, we prepared two samples using a silicon cubic mould (3 cm3).




                                                                                                      CONSERVATION SCIENCE IN CULTURAL HERITAGE
One sample was constantly monitored in order to establish the decrease in weight over
one day, finally calculating the total weight loss of the sample. The other sample was
utilized to find the decrease in volume during the drying process.

   2.2 Artificial aging

   In order to evaluate product performance over time and the ease with which they can
be removed, the stuccos were artificially aged. The assays were carried out on the previ-
ously described stucco samples; stucco was applied on the wooden samples (20´15.5´2
cm) from an ancient spruce girder (18th century). On each sample, a lacuna was ob-
tained (7´5´2 cm). Insulating material was layered on the wood surface before applying
the stucco, with the aim of preventing the adhesive from penetrating the wooden fibers.
   Finally, the samples colored by water colors were dried, in order to detect any al-
terations after the aging process. Artificial aging was carried out in an aging chamber
under UV rays, WEISS TECHNIK 500SB (T=22°C, RH=60-65%) for 2 months.

   2.3 Reversibility

   Solubility tests were carried out on artificially aged samples using three different
solvents, white spirits (ethers), acetone (ketones) and ethanol (alcohols), to find the
lowest polarity necessary to solubilize and remove the material.


                                                                                                123
                                                                                                                                       2.4 Microbiological susceptibility
F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                      Microbiological tests were performed (Figure 3) in order to verify the microbial sus-
                                                                                                                                    ceptibility of cellulose pulp, and evaluate if the artificial aging process would increase
                                                                                                                                    microbial development in the stucco [5].




                                                                                                                                    Figure 3. Preparation of microbial suspension in Nutrient Broth (a); inoculum on stucco sample (b).

                                                                                                                                       2.4.1 Microbiological assay n.1

                                                                                                                                       In order to determine susceptibility of the stucco to microbial colonization, we com-
                                                                                                                                    pared new stuccos with artificially aged stuccos.
                                                                                                                                       Aliquots of microbial culture were inoculated into the new cellulose pulp stucco sam-
                                                                                                                                    ples, prepared using different adhesives (rabbit glue, Klucel G, Tylose MH300P, Plextol
                                                                                                                                    B500, Beva D8S) [6, 7]. The same procedure was also carried out on the artificially
                                                                                                                                    aged samples, in order to observe potential differences in microbial growth between
                                                                                                                                    the new and aged samples. For each typology of stucco, five unaged samples and five
                                                                                                                                    aged samples were prepared. All samples were put into empty Petri dishes (9 mm in
                                                                                                                                    diameter). All tests were performed in a microbiological hood (laminar flow hood) in
                                                                                                                                    order to limit external contamination (Figure 4). Aliquots of 5 ml of different microbial
                                                                                                                                    suspensions, Aspergillus sp., Penicillium sp., Micrococcus sp. or Bacillus sp. (in Nutri-
                                                                                                                                    ent Agar liquid culture), were inoculated into each stucco sample. The samples were
                                                                                                                                    then incubated at 30°C for 14 days. Negative controls using stucco samples without
                                                                                                                                    inoculum were prepared.
                                                                                                                                       Micrococcus sp. and Bacillus sp. (bacteria), and Aspergillus sp. and Penicillium sp.
                                                                                                                                    (fungi) were tested, since these microbial species are frequently isolated on artwork
                                                                                                                                    surfaces.

                                                                                                                                       2.4.2 Microbiological assay n.2

                                                                                                                                       In the second test, we assessed the role of stucco components in microbiological
                                                                                                                                    colonization. For this purpose, six samples of cellulose, adhesive and stucco were
                                                                                                                                    prepared separately or mixed together (Figure 4). Aliquots of 5 ml of bacterial (Micro-
                                                                                                                                    coccus sp., Bacillus sp.) or fungal (Aspergillus sp., Penicillium sp.) suspension were
                                                                                                                                    inoculated into all samples and then incubated at 30°C for 14 days under wet condi-
                                                                                                                                    tions (Figure 5).
                                                                                                                                       The assay was also proposed for the 18th century spruce girder samples, previously
                                                                                                                                    used for reversibility tests and subjected to artificial aging. The wooden samples (with
                                                                                                                                    microbial inoculum) were incubated at 30°C for 14 days.




                                                                                                                              124
Figure 4. Different components used in the preparation of the stucco, cellulose and rabbit glue (on
the left); dry stucco (on the right).




                Figure 5. Inoculum of microbial suspension on wooden sample.




                                                                                                            CONSERVATION SCIENCE IN CULTURAL HERITAGE
   3. Results and Discussion

   The macroscopic features were investigated, during preparation, application, dry-
ing and mechanical finishing for each stucco sample and are summarized in Table 4.
   In terms of speed of drying, lightness and superficial finishing, the stuccos based
on cellulose ethers showed the best qualities, regardless of the solvents in which they
were dissolved. The advantage is the possibility to reduce and even eliminate the wa-
ter content of the stucco without changing its features.
   The best materials are the stuccos based on cellulose ethers dissolved in the mix-
ture of 50% water and ethanol (Klucel G and Tylose MH300 P). The doughs made of
acrylic adhesives cannot be adopted for use in the finish because they are difficult to
work mechanically once dried. Moreover, they can be better used for reintegration of
lacunae, in place of Araldite and Balsite.

   3.1 Shrinkage and weight loss in percentage

   The group of acrylic adhesives showed a moderate reduction in weight and no
shrinkage. On the other hand, the loss of weight in the cellulose ethers samples was
significant, equal to more than half of their initial value, while shrinkage was less or
equal to 0.5 cm (Table 1).


                                                                                                      125
                                                                                                                                        The acrylic adhesives, therefore, are characterized by low shrinkage; however, their
                                                                                                                                    weight should be taken into account, as adhesives are also used to fill large lacu-
F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                    nae; the stuccos made of cellulose ethers have opposite features. Table 2 reports the
                                                                                                                                    weights of both the wet and dry samples. Data show the weight loss of each sample
                                                                                                                                    following solvent evaporation, thus confirming the lightness of some adhesives with
                                                                                                                                    respect to others.
                                                                                                                                        The weight loss in the samples was different to that in the wooden supports, which
                                                                                                                                    was greater because of the adhesive absorption of the wood material.
                                                                                                                                        In particular it was observed that the lighter values in terms of weight loss (%) refer
                                                                                                                                    to cellulose ethers (72-78%), while the heavier values refer to acrylic resins (39%).
                                                                                                                                        For the samples made of cellulose ethers dissolved in ethanol, rapid weight loss
                                                                                                                                    was observed in 2 h. Weight loss involved in samples with major water content (rabbit
                                                                                                                                    glue or cellulose ethers) was slower, but these samples were lighter once dried.
                                                                                                                                        Stucco made of rabbit glue or Tylose MH300 P dissolved in water has high shrink-
                                                                                                                                    age and is lower in the sample prepared in water and ethanol (vol 1:1).

                                                                                                                                                             Table 1. Average shrinkage of dry samples.
                                                                                                                                     Stucco                                                                   Shrinkage (cm)

                                                                                                                                     RABBIT GLUE in H2O (1:14)                                                     0.8

                                                                                                                                     TYLOSE MH300 P at 5% in H2O                                                   0.5

                                                                                                                                     TYLOSE MH300 P at 5% in H2O/EtOH (1:1)                                        0.3

                                                                                                                                     KLUCEL G at 5% in EtOH                                                        0.4

                                                                                                                                     KLUCEL G at 5% in H2O/EtOH (1:1)                                              0.3

                                                                                                                                     AQUAZOL 200 at 25% in EtOH                                                    0.0

                                                                                                                                     PLEXTOL B500 (pure)                                                           0.1

                                                                                                                                     BEVA D-8-S (pure)                                                             0.1

                                                                                                                                                                 Table 2. Weight loss in dry samples.
                                                                                                                                                                               Weight              Weight                Weight loss
                                                                                                                                     Stucco
                                                                                                                                                                           wet sample (g)      dry sample (g)               (%)
                                                                                                                                     RABBIT GLUE in H2O (1:14)                  36.1                10.4                    73%

                                                                                                                                     TYLOSE MH300 P at 5% in H2O                31.1                    8.3                 73%
                                                                                                                                     TYLOSE MH300 P at 5% in H2O/
                                                                                                                                                                                33.6                    8.6                 74%
                                                                                                                                     EtOH (1:1)
                                                                                                                                     KLUCEL G at 5% in EtOH                     34.0                    7.4                 78%
                                                                                                                                     KLUCEL G at 5% in H2O/EtOH
                                                                                                                                                                                33.2                    9.3                 72%
                                                                                                                                     (1:1)
                                                                                                                                     AQUAZOL 200 (at 25% in EtOH)               37.0                14.7                    60%

                                                                                                                                     PLEXTOL B500 (pure)                        42.4                25.8                    39%

                                                                                                                                     BEVA D-8-S (pure)                          40.8                25.0                    39%



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   3.2 Artificial aging

   After the aging process, the differences between the samples were observed; some
samples were characterized by cracking and detachments from lacuna edges and
shrinkage of a few millimeters. The rabbit glue stuccos maintained their stability, re-
maining compact and planar, as in the Aquazol 200 stuccos. Some fissures, probably
due to less elasticity during the artificial aging, were observed in the Tylose MH300 P
stuccos.

   3.3 Reversibility

   The removal both of Tylose MH300 P and Aquazol 200 stuccos from lacunae in
wooden samples was prompt in ethyl alcohol. Plextol B500 and Beva D8S stuccos
were difficult to remove using solvents and it was necessary to remove them using
a mechanical action. Instead, removal of the rabbit glue stucco was easy and was
removed completely with the help of a scalpel (Figure 6). All solubility test results are
reported in Table 3.




                                                                                                           CONSERVATION SCIENCE IN CULTURAL HERITAGE
                              Figure 6. Tylose MH300P stucco removal.

                      Table 3. Solubility tests of adhesives after artificial aging.
                                 TYLOSE           TYLOSE
                   Rabbit                                            AQUAZOL      PLEXTOL   BEVA
                                 MH300 P         MH300 P at
                   glue in                                           200 at 25%     B500    D-8-S
                                 at 5% in        5% in H2O/
                  H2O (1:4)                                           in EtOH      (pure)   (pure)
                                   H 2O          EtOH (1:1)
 White spirit          1              1                1                 2             1      1
 Acetone               2              2                2                 4             3      3
 Ethanol               4              4                4                 4             2      2

1- No removal; 2- low removal; 3- partial removal; 4- good removal


   3.4 Microbiological susceptibility

  In microbiological assay n.1, microbial colonies developed on both aged and
new samples after 14 days of incubation. In particular, extensive microbial growth


                                                                                                     127
                                                                                                                                    was detected on rabbit glue samples, also due to the lack of a biocide agent. As a
                                                                                                                                    result, it appears that the aging did not favor microbial development. In the case
F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                    of the acrylic resins, no microbial growth was detected (Figure 7b) in the new
                                                                                                                                    samples, while the aged ones were characterized by some microbial colonization
                                                                                                                                    (Figure 7c) [8].




                                                                                                                                    Figure 7. Microbiological assay n.1. No artificial aged samples (a) before incubation and (b)
                                                                                                                                    after 14 days, Aspergillus colonies were developed. Inside red square: acrylic resin stuccos; c)
                                                                                                                                    Aspergillus spp. growing on aged samples.

                                                                                                                                       For microbiological assay n.2, no visible microbial growth was detected on the cel-
                                                                                                                                    lulose samples. On the rabbit glue samples, after 7 days we observed the presence
                                                                                                                                    of Aspergillus colonies and after 14 days we also detected Penicillium colonies, in
                                                                                                                                    addition to bacterial growth (Figure 8). Those samples containing both materials (i.e.
                                                                                                                                    stucco) were characterized by a slower growth (Figure 9) of Aspergillus and Penicillium
                                                                                                                                    colonies [9].




                                                                                                                                    Figure 8. a) Monitoring of Aspergillus spp. growth in adhesive from 7 days to 21 days; b) monitoring
                                                                                                                                    of Penicillium spp. growth in adhesive from 7 days to 21 days.

                                                                                                                                       These results highlight the susceptibility of glue to microbial colonization (due to its
                                                                                                                                    protein nature), while the cellulose was not subject to biodegradation.
                                                                                                                                       No biological growth was detected in the 18th century spruce girder samples after 14
                                                                                                                                    days and until today. The absence of microbial colonies is probably due to the absorp-
                                                                                                                                    tion of humidity that let the sample dry (Figure 10).


                                                                                                                              128
Figure 9. a) Monitoring of Aspergillus spp. growth on stucco sample (cellulose + adhesive) from 7
days to 21 days; b) monitoring of Penicillium spp. growth on stucco sample (cellulose + adhesive)
from 7 days to 21 days.




                                                                                                          CONSERVATION SCIENCE IN CULTURAL HERITAGE
Figure 10. Stuccos based on cellulose and different adhesives used for wood reintegration,
inoculated with microbial suspension: a) Plextol B500 (pure); b)BEVA D8 (pure);c) Aquazol 200
(25% in EtOH); d) Rabbit glue (1:14); e) Tylose (5% in H2O); f) Tylose (5% in H2O/EtOH [1:1]). F1
Aspergillus spp.; F2 Penicillium spp; B1 Bacillus spp.; B2 Micrococcus spp; B3 other bacterium;
C-control.

   The microbiological tests focused on the microbial susceptibility of cellulose-based
stuccos. The cellulose does not influence microbial colonization, which depends only
on the adhesive utilized to make the stucco. Evidently, adhesives based on protein
materials, such as rabbit glue, are more susceptible to microbial colonization than
acrylic ones. Moreover, the wooden tablets were not characterized by microbial colo-
nization. This represents an advantage if the stucco is utilized in reintegrating parts
of an artwork exposed in a museum, with optimal thermo-hygrometric conditions
(Table 4).




                                                                                                    129
                                                                                                                                                                 Table 4. Evaluation of microbial growth.
F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                             Material + Microbial inoculum             1st week         2nd week      3rd week
                                                                                                                                                   CELLULOSE + F1                          0                0            0
                                                                                                                                                   CELLULOSE + F2                          0                0            0
                                                                                                                                     CELL
                                                                                                                                                   CELLULOSE + B1                          0                0            0
                                                                                                                                                   CELLULOSE + B2                          0                0            0
                                                                                                                                                   RABBIT GLUE + F1                        1                3            3
                                                                                                                                                   RABBIT GLUE + F2                        0                2            3
                                                                                                                                     RB
                                                                                                                                                   RABBIT GLUE + B1                        0                1            1
                                                                                                                                                   RABBIT GLUE + B2                        0                0            1
                                                                                                                                                   STUCCO (CELL+RB) + F1                   0                1            1
                                                                                                                                                   STUCCO (CELL+RB) + F2                   0                1            1
                                                                                                                                     CELL+RB
                                                                                                                                                   STUCCO (CELL+RB) + B1                   0                0            0
                                                                                                                                                   STUCCO (CELL+RB) + B2                   0                0            0
                                                                                                                                      0-No growth; 1- trace of growth <10%; 2- low growth 10-30%; average growth 30-60%; high
                                                                                                                                           growth (> 60%). F1- Asperigillus; F2- Penicillium; B1- Micrococcus; B2- Bacillus



                                                                                                                                          4. Conclusions

                                                                                                                                        An important goal of this study is to demonstrate that aged cellulose pulp is not more
                                                                                                                                    susceptible to microbial colonization than new cellulose pulp. Another important aspect
                                                                                                                                    is that the microbial growth is attributable to the presence of the adhesive product.
                                                                                                                                        Some stuccos, such as rabbit glue and ether-based cellulose, have good superficial
                                                                                                                                    qualities, such as a good response to color. Acrylic-based stuccos, which are more
                                                                                                                                    compact and heavier, are recommended when the support is friable.
                                                                                                                                        Cellulose-based stuccos represent a valid alternative to commercial ones: cellulose
                                                                                                                                    has a lower elastic module than wood, avoiding the “wedge effect” in the structure, it is
                                                                                                                                    easy to work mechanically and can be utilized as a superficial stucco thanks to its high
                                                                                                                                    compatibility with the material.


                                                                                                                                          References

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        361-365.


      Biographical notes

    Fulvia Bartolone, Restorer of paintings and wooden sculpture. Master’s Degree
in Conservation and Restoration of Cultural Heritage at the University of Palermo,
awarded with 110 cum laude. She has worked in the Diocesan Museum of Palermo,
the Pepoli Museum of Trapani and churches and museums in different cities in Italy
and Europe. In 2015 she worked as restorer for the scientific collections of the Univer-
sity of Palermo. In the same year she won the fellowship “500 Giovani per la Cultura”




                                                                                                         CONSERVATION SCIENCE IN CULTURAL HERITAGE
of the Ministry of Cultural Heritage and Activities and Tourism (MIBACT) to work in the
Historical Archive of Palermo.
   Mauro Sebastianelli is a restorer. He trained at the Central Institute for Restoration
in Rome. Since 1993 he has carried out maintenance, preservation and restoration
work both at home in Italy and abroad. Since 2003, he has taught in the field of conser-
vation and restoration, for the educational service of the Superintendence dedicated to
the Roman network of Museums, at the educational workshop in the Galleria Borghese
in Rome. Since 2004 he has been a consultant for the conservation and restoration
of the Archdiocese and the Diocesan Museum of Palermo and since 2007, the Re-
gional Museum of Palazzo Mirto. Since 2007 he has also been a contract Restorer with
teaching activities on the degree course in Conservation and Restoration of Cultural
Heritage at the University of Palermo.
   Enza Di Carlo graduated in “Biological Science” at the University of Palermo and
specialized in “Microbiology and Virology” at the School of Medicine at the same uni-
versity. She is a Research Fellow at the Laboratory of Biology and Biotechnology
for the Cultural Heritage (LABBBC) of the Department of Biological, Chemical and
Pharmaceutical Sciences and Technologies (STEBICEF) at the University of Palermo,
where she carries out microbiological monitoring of environments for the preservation
and use of Cultural Heritage.


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                                                                                                                                        Giovanna Barresi graduated in “Science for Conservation and Restoration” at the
                                                                                                                                    University of Florence. She is a Research Fellow and works in the diagnostic-analytical
F. Bartolone, M. Sebastianelli, E. Di Carlo, G. Barresi, F. Palla, B. Megna - NEW APPLICATIONS IN THE USE OF CELLULOSE PULP




                                                                                                                                    field and applied research for the enzymatic cleaning of artifacts of historical-artis-
                                                                                                                                    tic interest at the Laboratory of Biology and Biotechnology for the Cultural Heritage
                                                                                                                                    (LABBBC) of the Department of Biological, Chemical and Pharmaceutical Sciences
                                                                                                                                    and Technologies (STEBICEF) at the University of Palermo.

                                                                                                                                        Franco Palla is Associate Professor of Applied and Environmental Botany at the
                                                                                                                                    University of Palermo, Italy. He is Professor and Coordinator of the Five-Year Degree
                                                                                                                                    in Conservation and Restoration of Cultural Property (MRL02, certified professional
                                                                                                                                    restorer). He is Scientific head of UNIPA Research Unit, for the Research Project
                                                                                                                                    PON01_00625, It@cha (Italian Technology for Advanced Applications in Cultural Heri-
                                                                                                                                    tage). He was one of the members of the working groups in the cooperation project
                                                                                                                                    Italy-Cambodia for Training Experts of Cultural Heritage, University of Palermo – Royal
                                                                                                                                    University of Fine Arts and the Ministry of Culture and Fine Arts, Angkor, Cambodia. He
                                                                                                                                    is Coordinator of the Laboratory of Biology and Biotechnologies for Cultural Heritage at
                                                                                                                                    the Department of Biological, Chemical, and Pharmaceutical Sciences and Technolo-
                                                                                                                                    gies (STEBICEF) of the University of Palermo.
                                                                                                                                       Bartolomeo Megna is a senior researcher of Science and Technology of Materials
                                                                                                                                    at the DICAM Department of Palermo; he has always been interested in the theme
                                                                                                                                    of conservation of cultural heritage; he has a PhD with a thesis on materials for the
                                                                                                                                    recovery of wooden artifacts.




                                                                                                                              132
    Summary
    Cellulose pulp, mainly utilized as a support for cleaning stone material, in this study,
is proposed as a filler for wooden supports. In the last 10 years, pulp has been used in
many restoration works carried out in the laboratory of the Diocesan Museum (MDP)
in Palermo, including both wooden sculptures and panel paintings. These artworks,
exhibited in the MDP, are constantly monitored in order to evaluate the effectiveness of
cellulose pulp as a filler, assessing its durability and bio-receptivity. In particular, struc-
tural characteristics, drying time, shrinkage, loss in weight, affinity to the pigments,
etc., were simultaneously evaluated. Tests were also carried out on artificially aged
cellulose pulp samples, in order to appraise if cellulose could be a source of nourish-
ment for microbial growth.


     Riassunto
     Il presente studio propone l’analisi e l’approfondimento di un materiale già noto nel
campo del restauro: la polpa di cellulosa, utilizzata da sempre come supportante per
impacchi di pulitura su materiale lapideo, qui analizzata in veste di stucco per supporti
lignei. Il materiale è stato utilizzato in alcuni interventi di restauro eseguiti nel labora-
torio del Museo Diocesano di Palermo nel corso degli ultimi 10 anni su sculture lignee
e dipinti su tavola. Le opere conservate in sale espositive costantemente monitorate
hanno permesso, fino ad oggi, di valutare l’efficacia dell’intervento. Lo studio propone
alcuni test eseguiti su campioni di stucco di cellulosa realizzati con leganti di origine
diversa, valutando le caratteristiche di ciascuna tipologia, i tempi di essiccamento,
ritiro, perdita in peso, affinità al colore, etc. Inoltre sono stati effettuati test d’invec-
chiamento, reversibilità e test microbiologici per determinare la resa della cellulosa
all’invecchiamento e valutare se il substrato in cellulosa possa costituire un supporto
alla colonizzazione microbica.




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