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Subject: Terracotta


From: Helena Jaeschke <helena.jaeschke>
Date: Friday, December 8, 2006
Robert B. Faltermeier <info [at] faltermeier__biz> writes

>I found the following statement on an other discussion group.
>   "Old terracotta's have manganese metallic traces that are easily
>    recognisable by visual inspection, they look like lichens and
>    can be used to authenticate."
>Has anyone researched this, is there a paper or article about this?

The Materials Research Society has a paper

    Caitlin R. O'Grady.
    Morphological and Chemical Analyses of Manganese Dioxide
    Accretions on Mexican Ceramics

    Abstract: Microscopic analysis of West Mexican ceramics (dating
    between in the collection of the Department of the Arts of
    Africa, Oceania and the Americas at the Metropolitan Museum of
    Art has established five different morphological types of
    manganese dioxide (MnO2) accretions. The accretions result
    mostly from a combination of bacterial and weathering activity
    in postdepositional contexts. Optical microscopy, scanning
    electron microscopy with energy dispersive x-ray analysis
    (SEM-EDS) and x-ray fluorescence (XRF) were successful; whereas
    microchemical spot tests, x-ray diffraction (XRD) and Raman
    spectroscopy proved inconclusive in the identification and
    differentiation of the five morphologies. Accretion morphology
    and substrate characteristics, together, suggest scenarios for
    the mechanism of formation and offer a qualitative tool for
    authentication. Accretions were documented using
    photomicrography, categorized based on empirical observations;
    sampled and analyzed using SEM-EDS and NDXRF.


It is free to members and can be purchased online by nonmembers for

    **** Moderator's comments: The above URL has been wrapped for
    email. There should be no newline.

Hope this helps,

Helena Jaeschke
Conservation Development Officer
Royal Albert Memorial Museum
Queen Street
Exeter EX4 3RX

                  Conservation DistList Instance 20:31
                Distributed: Saturday, December 9, 2006
                       Message Id: cdl-20-31-003
Received on Friday, 8 December, 2006

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