Detective Work:  Investigating art
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Detective Work: Investigating art Why?? to help direct restoration to help conservation to aid interpretation just to “know” “Is a painting ever done?” Ball, Time as Painter, Chapter 11 Methods: spectroscopy (“quantify interaction with light”)

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Detective Work: Investigating art Why?? to help direct restoration to help conservation

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Detective work investigating art why to help direct restoration to help conservation

  • Detective Work: Investigating art

  • Why?? to help direct restoration

    • to help conservation

    • to aid interpretation

    • just to “know”

  • “Is a painting ever done?” Ball, Time as Painter, Chapter 11

  • Methods:

    • spectroscopy (“quantify interaction with light”)

    • 2.chemical behavior ( “does it react?”)

    • 3. microscopy (“visual with a microscope”)


  • Detective work investigating art why to help direct restoration to help conservation

    The Basics of Spectroscopy:

    light source

    sample

    detector


    Detective work investigating art why to help direct restoration to help conservation

    Transmission

    Absorption

    light

    color

    “thrown away

    (observed)

    Reflection

    Absorption

    Transmission and Reflection effectively do the same thing: throw away unabsorbed colors


    Detective work investigating art why to help direct restoration to help conservation

    If the electromagnetic spectrum were a piano keyboard…..

    the visible spectral region would be just one key!

    “Light” is a term that refers to a electromagnetic radiation.

    And electromagnetic radiation are waves of different energies that extend over a broad range:

    frequency, Hz 10 26 10 24 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 10 2 Hz

    cosmic gamma X-rays UV Vis IR Radio induction power

    wavelength, nm 10 -8 10 -6 10 -4 10 -2 1 10 2 10 4 10 6 10 8 10 10 10 12 10 14 10 16 nm


    Detective work investigating art why to help direct restoration to help conservation

    light source

    sample

    detector

    interacts with light;

    “removes” (absorbs)

    some light components

    X-rays UV Vis IR

    Interaction type: electronic vibration

    Observed results: none none color heat

    Chromate, CrO42-

    “chromophore” in chrome yellow


    Detective work investigating art why to help direct restoration to help conservation

    X-rays UV Vis IR

    Interaction type: electronic vibration

    Observed results: none none color heat

    X-ray

    affects

    inner

    Electrons:

    Higher energy

    UV/vis

    affects

    outer

    electrons:

    Lower energy


    Detective work investigating art why to help direct restoration to help conservation

    X-rays UV Vis IR

    Interaction type: electronic vibration

    Observed results: none none color heat

    where in painting: penetrates all surfacebelow paint

    wavelength selected

    to interact most with

    black of underdrawing

    X-rays interaction

    strength depends

    on number of electrons:

    Pb >> Zn, Ti

    Lead white scatters X-rays

    more than zinc white or titanium white

    or most other pigments

    (except HgS or Ba-pigments)


    Detective work investigating art why to help direct restoration to help conservation

    Infrared Spectroscopy

    Instrumentation

    An infrared spectrophotometer is composed of:

    1) an IR light source, 2) a sample container, 3) a prism to separate light by wavelength, 4) a detector,

    and a recorder (which produces the infrared spectrum).

    SEE:

    Alizarin

    Carmine

    Indigo

    http://www.chemistry.ccsu.edu/glagovich/teaching/472/ir/instrumentation.html


    Detective work investigating art why to help direct restoration to help conservation

    Infrared Spectroscopy– compare two red dyes

    Alizarin

    Carmine


    Carmine cochineal

    CarmineCochineal


    Detective work investigating art why to help direct restoration to help conservation

    Feast of the Gods

    An analysis by WebExhibits

    • begin with historical context:

      • when did artist/work occur

      • workshop/atelier context and influences?

      • location

      • information on commission/motivation for work


    Detective work investigating art why to help direct restoration to help conservation

    Microscopy: What can you observe?

    Crystals? Shape: Are there faces or regular shapes or blobs?

    Large or small? Homogeneous or a mixture?

    Size? Pigment particles have characteristic size depending on how produced.

    Ground minerals are larger (and usually retain crystal morphology)

    Precipitated manufacture pigments are smaller (fine)

    High temperature processes (smalt) makes larger chunks,

    Color? There’s the obvious…. What color is it?

    Also, does reflected light have the same color as transmitted light?

    Or, is it pleichroic? (appears a different color in different orientations)

    Chemical reaction?

    Does it dissolve?

    Does it react / change with an acid? With a base?

    Refractive Index: relative measure of light velocity as it passes through pigment?

    Isotropy: isotropic?

    Anisotropic? Axial? Biaxial?


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