Studies in Conservation

Volumes 61(1) and 61(2) of Studies in Conservation were recently
published and are now available electronically, with print copies
currently being distributed to IIC (International Institute for
Conservation) members and institutional subscribers.

They contain the following papers:

61(1):

    Conservation strategy for food-based perishable art:
    Preservation versus reconstruction illustrated by Piece in Ghent
    by Jason Rhoades (1994)

    By Julie Gilman, Liesbeth Jacxens, and Bruno Demeulenaer

        The aim of this paper was to discuss the role of food
        preservation science and technology in the conservation of
        complex food-based installations.  By introducing the
        principles of food science and food preservation into the
        decision-making process for the conservation of contemporary
        art, more insight on conservation and presentation
        possibilities was created.  Considering the installation
        Piece in Ghent (P.I.G.) by Jason Rhoades, which contains
        French fries, the principles of food preservation science
        were evaluated.  The preservation of the original foods was
        discussed against the potential of a reproduction of the
        foods.  The context for conservation was determined by
        analysing the artist's intention, the production method of
        the artwork, and the degradation processes of the food
        materials.  From the results obtained, guidelines to
        preserve the 'original' foods were proposed, as well as
        guidelines to reproduce foods that can last longer.  The
        study demonstrated that food preservation science
        contributed to the development of effective strategies for
        the conservation of contemporary food-based art.

    Online event-based conservation documentation: A case study from
    the IIC website

    By Athanasios Velios

        There is a wealth of conservation-related resources that are
        published online on institutional and personal websites.
        There is value in searching across these websites, but this
        is currently impossible because the published data do not
        conform to any universal standard.  This paper begins with a
        review of the types of classifications employed for
        conservation content in several conservation websites.  It
        continues with an analysis of these classifications and it
        identifies some of their limitations that are related to the
        lack of conceptual basis of the classification terms used.
        The paper then draws parallels with similar problems in
        other professional fields and investigates the technologies
        used to resolve them.  Solutions developed in the fields of
        computer science and knowledge organization are then
        described.  The paper continues with the survey of two
        important resources in cultural heritage: the ICOM-CIDOC-CRM
        and the Getty vocabularies and it explains how these
        resources can be combined in the field of conservation
        documentation to assist the implementation of a common
        publication framework across different resources.  A case
        study for the proposed implementation is then presented
        based on recent work on the IIC website.  The paper
        concludes with a summary of the benefits of the recommended
        approach.  An appendix with a selection of classification
        terms with reasonable coverage for conservation content is
        included.

    The effect of modifiers on the stability of a vinyl
    acetate/ethylene copolymer dispersion

    By Jane L. Down

        This paper examines the effect of modifiers on the stability
        of a vinyl acetate/ethylene copolymer dispersion adhesive
        upon aging.  Eighteen common modifiers were added to a
        well-characterized vinyl acetate/ethylene copolymer
        dispersion (Dur-O-Set E-150) in known concentrations and
        dry-film samples were subjected to 16-17 years of dark aging
        and seven to eight years of light aging.  Yellowing, pH,
        gloss, swelling, cohesive strength, and flexibility were
        monitored for changes upon aging.  Generally, the neat
        Dur-O-Set E-150 (no additives) was found to become acidic on
        aging, but was fairly resistant to yellowing.  It also
        swelled substantially in toluene, was of high gloss, medium
        strength, and flexible, and remained so on aging.  No
        modifier was found to improve these properties.  Various
        solvents, wetting agents, and thickeners did not alter the
        properties by much, while plasticizers, freeze-thaw
        stabilizer, glycerin, and certain fillers had a more
        negative effect.

    Degradation of collagen in parchment under the influence of
    heat-induced oxidation: Preliminary study of changes at
    macroscopic, microscopic, and molecular levels

    By Kathleen Muhlen Axelsson, Rene Larsen, Dorte V.P. Sommer, and
    Rikke Melin

        This paper examines the impact of heat-induced oxidation for
        new and historical parchment with the purpose of improving
        diagnostic tools for use in practical parchment
        conservation.  Oxidation was generated by heat aging at 120
        deg. C in a dry oven for 24, 48, and 96 hours, respectively.
        The degradation was assessed on all samples at macro level
        by measuring color changes, at micro level by measuring the
        shrinkage temperature as well as by performing a visual
        assessment of the fibers' morphology and determining the
        amount of damaged fibers, and finally, at molecular level
        where amino acid analysis was used to reveal changes in the
        oxidized collagen.  The study shows that the heat-induced
        oxidation leads to significant color changes, decrease in
        hydrothermal stability, as well as changes in the amino acid
        composition.  Surprisingly, the results show that the
        historical parchment is more sensitive towards dry heat
        oxidation on a molecular level than is the new parchment.
        Furthermore, for the first time, we can show that physical
        damage reflected in the morphological characteristics of
        fibers can be attributed to oxidation by dry heat.

    A simple survey kit for chloride detection on cuneiform tablets
    and other collections

    By Dennis Piechota and Jane Drake Piechota

        This technical note describes the construction and use of a
        portable silver nitrate test kit designed to be safely
        usable in the storeroom during collection condition surveys.
        It provides the surveying conservator with supplementary
        test data to better predict the level of hazard presented by
        soluble salts in collections.

61(2):

    Technical replicas of Portuguese ceramic tile bodies produced in
    the Oporto region in the late nineteenth to early twentieth
    centuries

    By Marisa Costa, Paulo Cachim, Joao Coroado, and Ana Luisa
    Velosa

        Portugal is well known for its facades decorated entirely
        with ornamented glazed ceramic wall tiles called azulejos.
        On ageing, the tiles may detach and fall off, or deteriorate
        to such an extent that it becomes necessary to replicate
        them.  Hence tile replication is a common practice in
        Portugal for facade restoration, but very often these new
        tiles do not have the same physical and/or chemical
        properties as the original ones.  Such differences might be
        a factor in differential deterioration of the facades after
        restoration.

        One step toward an improvement in compatibility is to make
        new ceramic bodies with the same characteristics as the
        original ones.  This study focuses on two types of glazed
        ceramic wall tiles from the Oporto region in Portugal:
        'calcic faience' and po de pedra.  A total of 25 samples
        from the late nineteenth to early twentieth centuries were
        studied systematically as an attempt to improve knowledge of
        these materials and to create a basis for their replication.
        All samples were collected from facades that were under
        conservation/restoration at the time when sampling was
        performed.  The original traditional ceramic bodies were
        analyzed by X-ray diffraction and X-ray fluorescence.  Total
        open porosity, capillary absorption coefficient, and mercury
        intrusion porosimetry were also measured in order to gain
        knowledge on their physical characteristics in addition to
        their chemical and mineralogical compositions.

        High-temperature crystalline phases such as diopside,
        gehlenite, and mullite were found in the calcic faience,
        suggesting that the firing temperature of calcic faience
        bodies was within the range of 1100-1115 deg. C. Calcination
        trials were also performed in order to determine the most
        probable firing temperatures of the ceramic bodies.
        Collected data led to the assumption that the raw materials
        used for the ceramic bodies were kaolinitic clay, quartz
        sand, limestone, and talc.  The raw materials for po de
        pedra tiles were found to include kaolinite clay and quartz
        with firing temperatures estimated within the temperature
        range of 1150-1360 deg. C. Technical replicas made on the
        basis of these investigations were found to have the same
        mineralogical and capillary properties as the original
        tiles.

    Study of the deterioration products, gilding, and polychromy of
    the stones of the Scuola Grande di San Marco's facade in Venice

    By Fabrizio Antonelli, Lorenzo Lazzarini, Stefano Cancelliere,
    and Elena Tesser

        The Scuola Grande di San Marco is one of the most
        outstanding Renaissance buildings in Venice.  Destroyed by
        fire in 1485, the Scuola was reconstructed between 1487 and
        1495 by Pietro Lombardi (and sons), together with Giovanni
        Buora and Mauro Codussi.  The facade is considered one of
        the finest and most original exteriors of Venetian buildings
        and in particular features refined sculptural and painted
        decorations and a remarkable pictorial effect created by the
        extensive use of polychrome marbles and the false
        perspective view between the pilasters of the lower order.
        Most of the stone materials (Istrian and Verona red
        limestones, nero di Rovere, pavonazzetto toscano, Carrara
        marble and various reused antique marbles) present evident
        decay phenomena such as scaling, exfoliation, powdering,
        fissuring, salt efflorescence, black crusts, and artificial
        patinas of various kinds.  The present study reports the
        results of petrographic and chemical laboratory analyses
        carried out in preparation for the conservation treatment of
        the building, in order to characterize the main micro- and
        macro-morphologies of decay and to identify the causes and
        mechanisms of deterioration as well as the nature and
        application technique of the polychromy, gilding, and
        patinas present on parts of the monumental Renaissance
        facade.

    X-ray computed tomography for non-destructive analysis of early
    Medieval swords

    By Jarg Stelzner, Florian Gauass, and Philipp Schuetz

        the analysis of early Medieval swords is of great
        significance due to the eminent position of the find
        category in the study of the early Medieval period.  X-ray
        computed tomography is a non-destructive analytical method
        permitting the collection of data that otherwise could only
        be gathered with considerable effort and much damage to the
        object.  Beyond the usual morphological and dimensional
        parameters, the method allows for the fast and accurate
        gathering of knowledge about the construction and
        manufacturing processes of sword blades and can also be
        applied to block-lifted swords.  Preservation condition and
        related artifacts caused by beam hardening may be limiting
        factors; however, in most instances interpretation of the
        data remains possible.

    Confocal XRF depth profiling non-destructively reveals the
    original blue pigments in a Renaissance painting by Caroto

    By Myriam Eveno, Erin Mysak, Katharina Muller, Gilles Bastian,
    Nathalie Pincas, and Ina Reiche

        Recent restoration of The Rest on the Flight into Egypt by
        Giovanni Francesco Caroto, from the Louvre collections,
        included a technical examination of the Virgin's blue robe
        that aimed to characterize the original materials and later
        additions.  The painting was examined using light microscopy
        and ultraviolet and infrared imaging, and one cross section
        was taken.  None of these methods showed a clear distinction
        between the layers that were artist applied or modifications
        made by another hand.  To gain information about the paint
        stratigraphy without taking additional samples, non-invasive
        confocal X-ray fluorescence (CXRF) analysis was carried out
        to examine several areas of the Virgin's robe.  Using this
        technique, it was possible to identify the pigments and
        order of application of paint by the artist.  All the
        pigments identified were considered to be artist applied,
        and on this basis no further cleaning was carried out and
        conservation proceeded with retouching of minor areas of
        loss or damage.  This study highlights the advantages of
        CXRF analysis for the technical study of paintings, used in
        combination with classical methods for making informed
        conservation treatment decisions.

    Technical analysis of a Central Asian wall painting detached
    from a Buddhist cave temple on the northern Silk Road

    By Birgit Angelika Schmidt, Martin Andreas Ziemann, Simone
    Pentzien, Toralf Gabsch, Werner Koch, and Jarg Kruger

        A great number of Central Asian wall paintings,
        archeological materials, architectural fragments, and
        textiles, as well as painting fragments on silk and paper,
        make up the so called Turfan Collection at the Asian Art
        Museum in Berlin.  The largest part of the collection comes
        from the Kucha region, a very important cultural center in
        the third to ninth centuries.  Between 1902 and 1914, four
        German expeditions traveled along the northern Silk Road.
        During these expeditions, wall paintings were detached from
        their original settings in Buddhist cave complexes.  This
        paper reports a technical study of a wall painting, existing
        in eight fragments, from the Buddhist cave no. 40
        (Ritterhahle).  Its original painted surface is soot
        blackened and largely illegible.  Grunwedel, leader of the
        first and third expeditions, described the almost complete
        destruction of the rediscovered temple complex and evidence
        of fire damage.  The aim of this case study is to identify
        the materials used for the wall paintings.  Furthermore,
        soot deposits as well as materials from conservation
        interventions were of interest.  Non-invasive analyses were
        preferred but a limited number of samples were taken to
        provide more precise information on the painting technique.
        By employing optical and scanning electron microscopy,
        energy dispersive X-ray spectroscopy, micro X-ray
        fluorescence spectroscopy, X-ray diffraction analysis, and
        Raman spectroscopy, a layer sequence of earthen render, a
        ground layer made of gypsum, and a paint layer containing a
        variety of inorganic pigments were identified.

For information about joining the IIC or arranging for an
institutional subscription to Studies in Conservation contact:
iic<-at->iiconservation<.>org

Dr. Chandra L. Reedy
Editor-in-Chief, Studies in Conservation


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                  Conservation DistList Instance 30:2
                  Distributed: Saturday, May 28, 2016
                        Message Id: cdl-30-2-006
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