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Deterioration of Copper

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    Components of what may be an ancient battery. Iraq, first

    century CE. At left is the clay jar in which the iron rod (center)

    and copper cylinder (right) would have been placed. The dark

    fragments are bitumen, which would have been used to hold

    the three components together.

    Image courtesy of Department of Antiquities, Iraq.

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    Pourbaix diagram

    showing plot of

    natural aqueous

    environments with

    characteristics in

    different regions

    of Eh and pH.

    Image courtesy of Schweizer 1994 and David A. Scott .

    Deterioration of

    Copper

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    Pourbaix diagram showing distribution of natural aqueous

    environments, which can be seen to cover a considerable

    range of Eh and pH

    conditions. The dotted

    area represents the

    major concentrationof many thousands

    of Eh and pH

    measurements, while

    the surroundingirregular box

    represents the

    boundary for all

    measurements.

    Image courtesy of Baas Becking, Kaplan, and Moore 1960 and David A. Scott.

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    Image courtesy of David A. Scott.

    Agencya

    Soil type Years Corrosion(m/year) Maximum pitting(mm/year x 104)

    BNFMRA 5 least corrosive 10 0.5 - 2.5 Uniform: no pits

    BNFMRA 4 least corrosive 5 5.0 - 25 0.040

    NBS 9 least corrosive 14 4.0 - 2.5 0.043

    NBS 2 next mostcorrosive

    14 25 130 0.033

    BNFMRA Acid clay/acid peat 10 53 66 0.046

    BNFMRA 2nd series: b cinders 5 66 0.32

    NBS 3 most corrosive:rifle peat/tidal marsh

    14 160 355 0.115

    Analysis of corrosion of soils

    a BNFMRA = British Non-Ferrous Metals Research Association (now defunct); NBS = National Bureau of Standards.b 2nd series = second attempt to derive accurate results for this set of data.

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    Image courtesy David A. Scott.

    Name Formula Concentration (ppb)

    Ozone O3 50 200

    Hydrogen peroxide H2O2 10 -30

    Nitrogen dioxide NO2 10 45

    Nitric acid HNO3 1 10

    Hydrogen sulphide H2S 0.1 0.5

    Carbonyl sulphide COS 0.5 0.6

    Sulphur dioxide SO2 5 24

    Carbon dioxide CO2 (3 6 ) x 105

    Formic acid HCOOH 0.2 1

    Acetic acid CH3COOH 0.2 1

    Oxalic acid (COOH)2 Not detected

    Formaldehyde HCHO 4 15

    Acetaldehyde CH3CHO 1 8

    Hydrogen chloride HCl 0.5 - 2

    Typical Modern Concentrations Atmospheric Gases

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    Image courtesy of David A. Scott.

    Conversion factors for concentrations of some pollutantgases in parts per billion (ppb) and microgram/m3 (g/m3)

    Name Conversion Factor a

    ppb to g/m3 g/m3 to ppb

    Acetic acid 2.45 0.41

    Formic acid 1.88 0.53

    Acetaldehyde 1.80 0.56

    Formaldehyde 1.23 0.82

    Hydrogen sulphide 1.39 0.72

    Carbonyl sulphide 2.45 0.41

    Ammonia 0.70 1.44

    Sulphur dioxide 2.62 0.38

    Nitrogen dioxide 1.88 0.53

    Ozone 1.96 0.51

    a The general expression is microgram/m3 x conversion factor = ppb. All measurements are at standard temperatureand pressure, with temperature assumed to be 25C.

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    Stability diagram of thesystem Cu-SO4-H2O with

    fog and rain areas shown

    for urban atmospheres.

    Area A = atacamite

    stability; area B =

    brochantite stability.

    Although the diagram

    over-simplifies the actual

    situation, it does showthat brochantite should

    form in outdoor exposure

    an that antlerite may

    form in more acidicconditions. Image courtesy of Graedel 1987 and David A. Scott.

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    Copper

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    Building SO2

    (ppm)

    O3

    (ppm)

    NOX

    (ppb)

    NO

    (ppm)

    Dates

    National Gallery, London 0.25

    Victorian and Albert Museum, London 3 42 1983

    Tate Gallery, London < 4 1980 83

    Sainsbury Center, Norwich, U.K. 40 (max) 1981

    National Archives and RecordsAdministration, Fort Worth, Texas

    2 25 < 42 10 252

    National Gallery, Washington, D.C. < 1 Low 7 50

    Library of Congress, Washington, D.C. < 0.5 Low 4 145

    Baxter Gallery, Pasadena, California 120 1982

    Los Angeles County Museum of Art, LosAngeles, California

    < 10 1982

    Huntington Gallery, San Marino, Calif. < 10 1982

    Scott Gallery, San Marino, California 31 92 32 1964

    Huntington Library, San Marino, Calif. 75 37

    Rijksmuseum, Amsterdam 1 5 1974

    Concentration of air pollutants in museums and libraries

    Image courtesy of Brimblecombe 1990 and David A. Scott.

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    Building SO2(ppm) O3(ppm) NOX(ppb)

    NO(ppm)

    Dates

    Rijksarchief, The Hague < 1 < 1 30 1986

    Rijksarchief, Arnhem 1 2 16 1986Rijksarchief, Leewwarden < 1 < 1 ~ 7 1986

    Concentration of air pollutants in museums and libraries

    Summer measurements

    Building SO2(ppm) O3(ppm) NOX(ppb)

    NO(ppm)

    Dates

    Rijksarchief, The Hague 1.5 49 1986

    Rijksarchief, Arnhem 4.5 39 1986

    Rijksarchief, Leewwarden < 1 ~ 46 1986

    Winter measurements

    Image courtesy of Brimblecombe 1990 and David A. Scott.

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    Marine zone Environment Characteristic behavior of copper

    Atmospheric Small sea-salt particles carried by wind.Corrosivity varies with height abovewater, dew cycle, bird droppings, wind,etc.

    Partially sheltered surfaces maydeteriorate more rapidly than thoseexposed; top surfaces may be washed freeof salt by rain.

    Splash Wet, well-aerated surface, no fouling. Most aggressive zone for may metals andfor protective coatings.

    Tidal Marine fouling present to high water. Copper may act cathodically at tidal zone.

    Shallow water Seawater saturated with oxygen;pollution, sediment, and fouling may all

    be present.

    Corrosion may be more rapid than inexposed marine zone areas; a layer of hardshell and biofouling may restrict corrosion.

    Continental shelf No plant fouling; some decrease inoxygen, especially in the Pacific, and atlower temperatures.

    Copper alloys may be well preserved.

    Deep ocean Oxygen varies, lower here than atsurface; temperature near 0C; velocityand pH both lower than at surface.

    Data for copper alloys sparse, butcorrosion is limited.

    Mud Sulfate-reducing bacteria present;bottom sediments vary in origin,characteristics, and corrosion behavior.

    Partially buried bronzes corroded most;submerged copper alloys may be severelyattacked.

    Typical marine environments

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    Mineralname

    Formula Crystal system Color Mohshardness

    Cuprite Cu2O Cubic Submetallic red 3.5 4

    Tenorite CuO Monoclinic Metallic gray black 3.5

    Spertiniite Cu(OH)2 Often amorphous Blue green 1 2 ?

    Characteristics of some copper oxide and copperhydroxide minerals

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    Pourbaix diagrams for the system Cu-CO3-H2O at various

    carbon dioxide concentrations

    44 ppm 440

    ppm

    4400 ppm 44000 ppm

    Images courtesy of Pourbaix and David A. Scott.

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    Illustration of natural

    azurite and malachite

    crystal forms

    Image courtesy of Palache, Berman, and Frondel 1951 and David A. Scott.

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    Mineral name Formula Crystalsystem

    Color Mohshardness

    Malachite CuCO3 . Cu(OH)2 Monoclinic Pale green 3.5 4

    Azurite 2CuCO3 . Cu(OH)2 Monoclinic Vitreous blue 3.5 4

    Georgeite CuCO3 . Cu(OH)2 Monoclinic Pale blue ?

    Chalconatronite Na2Cu (CO3)2 . 3 H20 Monoclinic Greenish blue 3 -4

    Rosasite (Cu, Zn)2CO3(OH)2 Monoclinic Bluish green 4.5

    Aurichalcite (Cu, Zn)5(CO3)2(OH)6 Orthorhombic Pearly pale green 1 2

    Claraite (Cu, Zn)3(CO3)(OH)4 .4H2O

    Hexagonal Translucent blue 2

    Characteristics of some basic carbonate minerals

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    Shang Dynasty ding,

    bronze, shown after

    electrolytic stripping.

    Image courtesy of Honolulu Academy of the Arts.

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    Copper

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    Shang Dynasty ding,

    bronze, middle Anyang

    period.

    Detail, Shang Dynasty

    ding. Note black inlay.

    Image courtesy of Honolulu Academy of the Arts.

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    Copper

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    Shang Dynasty xian

    steamer vessel, bronze.

    Note black soot on

    bottom.

    Image courtesy of Honolulu Academy of the Arts.

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    Copper

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    Western Zhou Fugeng Li

    ding, bronze. 1100-1000

    B.C.E.

    Image courtesy of Arthur M. Sackler Gallery, Washington D.C.

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    Early Western Zhou

    Dynasty hu, bronze, 11th

    to early 10th century

    B.C.E. Photographed

    before acquisition by the

    Freer Gallery of Art.

    Image courtesy of Freer Gallery of Art, Washington, D.C.

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    Same Western Zhou

    Dynasty hu, photographed

    after acquisition by the

    Freer Gallery of Art. Note

    darker area of corrosion

    products where lid joins

    vessel.

    Image courtesy of Freer Gallery of Art, Washington, D.C.

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    Copper

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    Zhou Dynasty gui, bronze, shown during treatment with

    cleaned section on the right.

    Image courtesy of Freer Gallery of Art, Washington, D.C.

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    A. Milne Calder, bronze

    statue of William Penn,

    cast 1889-91, City Hall

    Tower, Philadelphia.

    Image courtesy of Andrew Lins and Tracy Power

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    Copper

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    BF x96 from the William Penn figure: a complex, multilayer

    corrosion crust can develop on bronzes after long exposure to

    urban-industrial atmospheres in this case 97-98 years. The

    corrosion is approximately 200 microns thick and partly

    follows

    microstructuralfeatures, especially

    casting pores

    located near

    the surface.

    Image courtesy of Andrew Lins and Tracy Power

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    BF x240 also from the William Penn figure, illustrates that

    the delta phase is not as rapidly attacked as the alpha phase

    at this particular site.

    Image courtesy of Andrew Lins and Tracy Power

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    BF x310 shows the irregular, porous nature of the mineral

    formations within the crust.

    Image courtesy of Andrew Lins and Tracy Power

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    This three-dimensional plot shows the stability of different

    copper minerals in water at 25C. Below are oxidized copper

    species found in rain or natural waters. The x axis shows pH,

    the y axis shows

    sulfate ion activity,

    and the z axisshows total CO2

    activity (including

    CO2(g), H2CO3,

    HCO3-

    , and CO3=

    ).Zone of conditions

    favoring antlerite

    formation is

    shaded.

    Image courtesy of Andrew Lins and Tracy Power

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    Plot emphasizing the calculated lower limit of cupric ion

    activities (aant v broch) which would allow antlerite rather than

    brochantite to form,

    based on the work

    of Silman.

    Image courtesy of Andrew Lins and Tracy Power

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    Plot showing the solubility of different copper sulphate and

    oxide species in dilute sulphuric acid solutions. Data basedon thermodynamic and

    other calculations at 25C,

    after Mattson and Graedel.

    Zones for acid rain and fog

    are displayed, overlaps

    indicating which minerals

    are likely at particular pH

    levels and sulphate

    concentrations. The leftside shows no stable

    mineral forms, only

    Cu++ in solution.

    Image courtesy of Andrew Lins and Tracy Power

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    The site of Francavilla, Southern Italy, 5th-6th C BC.

    Bronze tripod legs of anthropomorphic form.Image courtesy of Bolletino dArte.

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    The site of Francavilla

    Image courtesy of Bolletino dArte.

    From left to right,

    top to bottom:

    Extensive working and

    annealing to shape,

    followed by cold-working of

    the surface.

    Very small crystallized

    grains. Copper sulfideinclusions are visible.

    Variable grain size with

    intergranular corrosion.

    Typical corrosive

    penetration along slip

    planes in the bronze

    crystals infilled with cuprite.Corrosion crust principally

    of malachite.

    Uneven intergranular

    attack.

    Overall view.

    Recrystallized small grain

    structure.

    Sulphide and leadinclusions and very large

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    Pourbaix diagrams for the system Cu-Cl-H2O at various

    carbon dioxide concentrations

    35 ppm 350

    ppm

    3550 ppm 35500 ppm

    Images courtesy of Pourbaix and David A. Scott.

    Deterioration of Copper

    D t i ti

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    Pourbaix diagram for

    the system Cu-SO4-H2O.

    Images courtesy of Pourbaix and David A. Scott.

    Deterioration

    of Copper

    D t i ti

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    Pourbaix diagram for

    the system Cu-S-H2O.

    Image courtesy of Schweizer.

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    of Copper

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    Images courtesy of David A. Scott.

    Surface corrosion

    containing pustules of

    copper and lead salts.

    Surface of the Roman

    bronze statue of Romaor Virtus showing

    fibrous malachite

    occurring as curled

    crystals.

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    Image courtesy of the Getty Museum.

    Miniature Portrait Bust

    of a Woman, Roman,25 BC - 25 AD. Bronzewith glass-paste inlays.

    The bust is shown

    before conservation,

    illustrating pustularcorrosion with pitting

    created by bronze

    disease.

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    Images courtesy of David A. Scott.

    Two small penannular bronze nose ornaments from the site of La

    Compania, Ecuador, dated to about the tenth century CE, showing the light

    green, powdery eruptions typical of bronze disease.

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    Measures for wet metallic objects: bronze, brass, lead and

    silver can generally be allowed to dry out. Iron may be

    better stored in oxygen-free environment, can use oxygen

    scavengers in sealed jar or box, silica gel, or store in water

    with sulphite added to mop up oxygen. Silica gel may not

    be enough for heavily corroded iron.

    Deterioration of Copper

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    The monument of MarcusAurelius after restoration

    Image courtesy of The Mr. and Mrs. Lawrence Fleischman.

    Before

    After

    Deterioration

    of Copper

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    Elemental distribution

    maps for sulfur, lead, tin

    and carbon, together with

    secondary-electron and

    backscattered electron

    images (top).

    Magnesium, copper,

    chlorine and oxygen with

    secondary-electron andbackscattered electron

    images (bottom) for a de

    Vries bronze statue.

    Images courtesy of David A. Scott.

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    Elemental distribution

    maps for a bronze

    statue of Alexander

    Hamilton, New York,

    erected 1890:

    Copper(top left)

    Tin (top center)

    Chlorine (top right)

    Oxygen (bottom left)

    Zinc (bottom center)Images courtesy of David A. Scott.

    Deterioration of Copper

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    Image courtesy of David A. Scott.

    Togati pustule

    Deterioration

    of Copper

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    Image courtesy of David A. Scott.

    Togati pustule

    Deterioration

    of Copper

    D t i ti f C

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    Votive bronze leaf

    Narrow leaf formed of thin sheet

    bronze, with a prominent central rib.

    Bottom: view of a section of leaf

    showing voids that suggest selective

    corrosion of the alloy due to

    differential composition.

    Image courtesy of David A. Scott.

    Magnificationx100, crossed

    Deterioration of Copper

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    Bronze flower rosette.

    Six joining frr preserving much

    of rosette. Rosette with at

    least eight petals, and

    perhaps originally as many as

    eleven. Hole in center; nopreserved rivet

    Image courtesy of Bolletino DArte: the Archaic Votive Metal Objects.

    Deterioration of Copper

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    Right: Overall view of rosette, unetched,

    showing cracking and inter-granularcorrosion.

    Bottom right: View of etched section

    showing small twinned grains and inter-

    crystalline corrosion.

    Bottom: etched in ammonia peroxide

    showing strain lines in the surface areas.

    Magnification x50

    Image courtesy of Bolletino DArte: the Archaic Votive Metal Objects.

    Magnification

    x250

    Magnification

    x100

    Deterioration of Copper

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    Bronze votive floral sprays.

    Two joining flowers, plus

    miniscule flower, preserving

    complete rod, with portions of

    terminals at both ends. Bent,

    as shown. Somewhatcorroded.

    Image courtesy of Bolletino DArte: the Archaic Votive Metal Objects.

    Deterioration of Copper

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    Right: View of votive floral spray

    showing the corrosion crust tat

    displays extensive Liesegang-type

    phenomena in a cuprite and

    malachite crust.

    Bottom right: Etched view

    showing twinned grains with

    corrosion through strain lines.

    Magnification

    x12.5

    Image courtesy of Bolletino DArte: the Archaic Votive Metal Objects.

    Magnification

    x100

    Deterioration of Copper

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    Preserve unique version of

    Greek language.

    Made in pure copper

    Corrosion considered odd

    Thought to be a forgery by

    some German scientists

    Need to confirm their

    authenticity as very important

    for the history of language.

    One plaque in Johan von

    Wagner Museum: Stuttgart,

    another two in Norway, one

    lost in a private collection.

    Image courtesy of West Semitic Research.

    Copper plaque.

    Deterioration

    of Copper

    G k C Pl

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    Greek Copper Plaques

    Image courtesy of West Semitic Research.

    Copper plaque.

    Deterioration

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    Radiographic examination used

    to read inscribed text on backand front without further

    cleaning.

    Chemical analysis

    X-ray fluorescence studies X-ray diffraction studies

    Metallographic studies

    Here the hammering marks in

    the x-ray image are importantas same on all three plaques.

    Text is from 8th-9th century BC

    Greek evolving from Phoenician

    at this time. Get digamma and

    qoppa used.Image courtesy of West Semitic Research. Copper plaque, X-radiograph.

    Deterioration

    of Copper

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    Corrosion on one very

    heavily chloride-

    containing.

    This was atacamite and

    paratacamite, two of the

    copper trihydroxychlorides

    Cu2(OH)3Cl.

    German argument was

    that this is not acceptable.

    Argument based on usual

    predominance of

    malachite and carbonates

    in soil burial corrosion.

    Image courtesy of West Semitic Research.

    Copper plaque.

    Deterioration

    of Copper

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    Detailed surface examination showed inscribed letters

    preserved within corrosion, not metallic substrate.

    Image courtesy of West Semitic Research.

    Copper

    plaque,

    detail of

    inscription

    s.

    Deterioration of Copper

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    ESEM studies showed pseudomorphic preservation of wood

    cellular structure within copper corrosion products of malachite.

    Note spiral thickening of cell wall and some pits.

    Image courtesy of West Semitic Research.Copper plaque. Copper corrosion has replaced the wood

    Deterioration of Copper

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    Minute wood and some charcoal fragments preserved within

    corrosion crust.

    Image courtesy of West Semitic Research.Copper plaque with attached

    Deterioration of Copper

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    More examples of pseudomorphic preservation of cellular

    wood structure.

    Images courtesy of David A. Scott.

    Deterioration of Copper

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    Metallographic examination reveals coherent cuprite layer

    beneath thick green corrosion crust contiguous with metal

    Image courtesy of West Semitic Research.Copper plaque microstructure.

    Deterioration of Copper

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    Mineralogical complexity to this corrosion crust

    Image courtesy of West Semitic Research.Copper plaque microstructure.

    Deterioration of Copper

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    Argument for authenticity too

    strong: Surface preserved within corrosion.

    Coherent cuprite layer

    Pseudomorphic replacement of

    wood

    Hammering marks of the plaques

    Knowledge that pure copper was

    used for other artefacts

    Corrosion acceptable

    Conclusion: previous view thatplaques are fake is totally incorrect.

    Based on a superficial view that

    patinas primarily of copper

    chlorides do not exist, which is

    Deterioration

    of Copper


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