Studies in Conservation

Volume 59(1) (January 2014) of Studies in Conservation was recently
published and is now being distributed to IIC (International
Institute for Conservation) members and institutional subscribers.
This is a themed issue on Paintings Imaging and Cleaning Issues,
with an introductory editorial by Joyce H. Townsend, IIC Director of
Publications. It contains the following five papers:

"A note on the construction of test panels for the spectral imaging
of paintings"

    Anna Moutsatsou
    National Gallery - Alexandros Soutzos Museum, Athens, Greece

    Athina Alexopoulou
    Faculty of Fine Arts and Design, Department of Antiquities and
    Works of Art Conservation, Technological Educational Institute
    of Athens, Aigaleo, Greece

    The construction and examination of test panels is an ad hoc
    procedure, necessary for every spectral imaging study of
    paintings. Despite the common features, almost every scientific
    team follows a different way of construction. Furthermore, many
    of these approaches are not adequately documented in the
    relevant papers. Failure to use common language and practice
    leads to confusion about properties of materials and paint
    layers that have been overall examined by the scientists, as
    well as the validity of the results and their exploitation in
    several conservation applications. The present theoretical
    approach points out the need for common protocols for the
    construction of test panels and draws general principles as a
    flow chart on which they should be based.

"Radiography of paintings: Limitations of transmission radiography
and exploration of emission radiography using phosphor imaging
plates"

    Olivier Schalm, Lies Vanbiervliet
    Artesis University College of Antwerp, Conservation Studies,
    Antwerpen, Belgium

    Peter Willems
    Industrial and Scientific Consulting, Stekene, Belgium

    Peter De Schepper
    3GE Measurement and Control Systems, Berchem, Belgium

    Radiography in transmission mode is a well-established technique
    to visualize the internal structure of paintings. However, for
    many paintings the pictorial layer cannot be clearly visualized
    with conventional radiography because of interference from paint
    on the reverse, the material composition, or the regular
    structure of supports or subsurface layers. Traditional lead
    white grounds in particular cause specific imaging problems not
    encountered with more modern white pigments such as zinc and
    titanium whites. A solution to this problem is radiography in
    emission mode. This study demonstrates and articulates those
    factors that can interfere with visualization of a painting's
    pictorial layer using transmission radiography as well as those
    that contribute to the effectiveness of emission radiography in
    visualizing such information. While emission radiography has
    been applied to the examination of paintings for over half a
    century, it is a cumbersome technique that is further
    complicated by the need to work under dim safelight illumination
    when X-radiographic film is used. Therefore, the use of computed
    radiography using storage phosphor imaging plates for emission
    radiography was also investigated.

"Parametrization of the solvent action on modern artists' paint
systems"

    Stefan Zumbuh
    Department of Conservation and Restoration, Bern University of
    Applied Sciences BFH, Bern, Switzerland

    A solvent action parametrization scheme has been developed
    combining relevant parameters of the solvent action on modern
    artists' paints to characterize the solvation and dissolving
    properties of different binding media. The new system combines
    different concepts used in solvent chemistry. It is based on the
    normalized and solute-dependent dimension [h delta-H +
    eET(30)cv]N.

    It comprises a polarity value ET(30)cv as the magnitude of the
    enthalpy, and a combined value representing the cavitation
    energy delta-H as an entropy-influencing factor. Forty-eight
    solvents were divided into five subgroups based on their
    interaction and structural properties. This binary scheme
    permits one to reliably quantify spaces of efficiency. The
    graphical selectivity of the scheme was applied to four binding
    media systems (oil, alkyd, acrylic-, and acrylic-polystyrene) by
    determination of the swelling capacity of 48 solvents. The
    graphical visualization of the systematic parametrization of
    solvents permits one to judge the intermolecular interaction and
    other effects of solvation relevant to the restoration of
    painted artwork.

"A cause of water-sensitivity in modern oil paint films: The
formation of magnesium sulphate"

    Genevieve Silvester, Aviva Burnstock
    Department of Conservation and Technology, Courtauld Institute
    of Art, London, UK

    Luc Megens
    Netherlands Cultural Heritage Agency (RCE), Amsterdam, The
    Netherlands

    Tom Learner, Giacomo Chiari
    Getty Conservation Institute, Los Angeles, CA, USA

    Klaas Jan van den Berg
    Netherlands Cultural Heritage Agency (RCE), Amsterdam, The
    Netherlands

    Unvarnished twentieth-century oil paintings are often sensitive
    to aqueous swabbing, a method routinely employed by conservators
    for surface cleaning. This study proposes a connection between
    sensitivity and the presence of magnesium sulphate heptahydrate
    which has been identified on the surface of some of
    water-sensitive paintings. The probable source of magnesium is
    magnesium carbonate, an additive in some twentieth-century oil
    paints, which has reacted with atmospheric sulphur dioxide
    (SO2). Films made using modern manufactured paints and
    formulations made in the laboratory were exposed to gaseous SO2
    and raised relative humidity and examined using scanning
    electron microscopy with energy dispersive X-ray spectroscopy
    and X-ray diffraction to characterize the crystalline entities.
    Films containing magnesium carbonate formed magnesium sulphite
    and sulphate hydrates. Films containing zinc oxide were also
    investigated. These formed zinc and sulphur containing salts.
    Sensitivity to swabbing with water before and after exposure was
    evaluated. Films that developed salts demonstrated increased
    sensitivity to aqueous swabbing after exposure to SO2. Findings
    suggest that increased water sensitivity may be due to a
    combination of the formation of hygroscopic degradation products
    and to weakening of the paint film due to salt-induced
    disruption of the surface.

"Acrylic emulsion paint films: The effect of solution pH,
conductivity, and ionic strength on film swelling and surfactant
removal"

    Courtney E. Dillon, Anthony F. Lagalante,
    Department of Chemistry, Villanova University, PA, USA,

    Richard C. Wolbers
    Department of Art Conservation, University of
    Delaware, DE, USA

    To date, a limited number of aqueous conditions have been tested
    experimentally as potential cleaning reagents on modern acrylic
    paint films. Those assessed have tended to extract measurable
    quantities of paint film components and distort the paint films
    physically. In this paper the results of a series of experiments
    designed to examine pH, conductivity, and specific ion effects
    of potential aqueous cleaning solutions on a series of
    commercial acrylic paints are reported. A three-dimensional
    microscopic technique was used to characterize the physical
    (volume and surface roughness) changes and liquid
    chromatography-tandem mass spectrometry was used to characterize
    the chemical (extracted surfactant) changes following paint film
    exposure to the aqueous solution. The tested paint films in this
    study clearly exhibit an isotonic point below which swelling and
    extraction is significant, and above which the swelling and
    extraction is diminished. Manipulation of conductivity and the
    ionic species in solution can reduce both the physical film
    changes and surfactant extraction from acrylic paint films;
    while pH appears to be of limited use in controlling aqueous
    cleaning effects. Moreover, there seems to be a specific ion
    effect for both swelling and de-swelling in acrylic paint films
    that can be rationalized through the Hofmeister Series.

The electronic version of this issue can be accessed by logging onto
the IIC website

    <URL:https://www.iiconservation.org>

as a member, then clicking on Resources/Publications. Under the
entry for Studies in Conservation, follow the link to Maney Online.

Or, log onto Maney Online directly by going to:

    <URL:http://www.maneyonline.com/loi/sic>

Institutional members may need to refer to their library for
password information.

While at the Studies in Conservation Maney Online website, please
click on the link to Advance Articles and peruse the more than 30
papers that have been accepted but have not yet appeared in an
issue. These papers are made available to IIC members and
subscribers shortly after they are accepted so this is a good place
to learn about cutting edge work. Also, please explore the new
search capabilities of Maney Online and search by author, keyword,
etc. through all issues back to Vol. 1, 1954, including all past IIC
conference proceedings, which have now been digitized and can be
found as supplements to the Studies volume of the year in which the
conference took place.

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


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