X-Ray Fluorescence
X-ray fluorescence (XRF) is a non-destructive technique that provides elemental information (generally for elements that have an atomic weight above aluminum) that is representative of an artwork's surface. When applied to paintings, XRF can identify the presence of certain pigments (inorganic materials) using an x-ray energy source to help answer questions relating to authenticity and provenance. As the technique does not require sampling, XRF is an excellent preliminary method that can be used to help determine whether additional sampling is necessary. Today XRF units can be found in museums and institutions worldwide, with nearly 1500 units being used for cultural heritage applications.
Care should be taken when interpreting results as peaks can arise from other sources (such as the instrument itself): therefore consultation with a conservation scientist is essential. Other complications such as the use of metal driers (e.g. driers containing lead or manganese), pigments in underlying paint layers, and mordants present in organic colorants (e.g. Ca, Sn) can lead to misinterpretation. While the technique is relatively easy to perform, data interpretation is often more complicated and requires familiarity with both the artwork and the system being used.
A Bruker Handheld Tracer-III XRF spectrometer was used to collect the XRF spectra from various locations (spectra obtained by Kristen Watts and Dr. Amanda Norbutus from Villanova's Chemistry Department; interpretation by project leader Kristin deGhetaldi).
Blue Sky 1
Blue Sky (Before Cleaning Test) - Possible Pigments: Lead White, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Blue Sky 2
Blue Sky (After Cleaning Test) - Possible Pigments: Lead White, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Green Dress
Green-Blue Dress - Possible Pigments: Lead White, Green Earth, Iron Oxides (Ground Layers), Calcium Sulphate/Carbonate
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Green Leaf
Possible Pigments: Green Earth, Lead White (attentuated peaks indicate Lead is in lower layers), Iron Oxides (Ground Layers), Calcium Sulphate/Carbonate
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Woman's Flesh
Woman's Flesh (Before Cleaning) - Possible Pigments: Lead White, Vermillion, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Blue Drapery
Blue Drapery (Before Cleaning) - Possible Pigments: Lead White, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White and Chromium Yellow/Red (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Yellow Skirt
Possible Pigments: Lead White, Iron Oxides, Calcium Sulphate/Carbonate, Vermillion
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Soldier's Red Cloak
Red Drapery - Possible Pigments: Lead White/Red Lead, Iron Oxides, Vermillion, Calcium Sulphate/Carbonate
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Yellow Tunic
Possible Pigments: Lead White, Iron Oxides, Vermillion, Calcium Sulphate/Carbonate, Barium White (Overpaint), Chromium Red/Yellow and Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Leg of Soldier
Possible Pigments: Lead White, Iron Oxides (Umbers), Vermillion, Calcium Sulphate/Carbonate
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Yellow Sash
Possible Pigments: Lead White/Naples Yellow, Iron Oxides, Vermillion, Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
David's Green Drapery
Possible Pigments: Lead White, Green Earth/Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Pink Shirt
Possible Pigments: Lead White, Iron Oxides, Vermillion, Calcium Sulphate/Carbonate, Zinc White and Barium White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Column
Possible Pigments: Lead White, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Woman with Tambourine
Possible Pigments: Lead White, Vermillion, Iron Oxides, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Red Floor Tile
Possible Pigments: Lead White, Vermillion, Iron Oxides (Umbers), Calcium Sulphate/Carbonate, Azurite (?), Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Blue Cloak
Possible Pigments: Lead White, Iron Oxides, Calcium Sulphate/Carbonate
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF
Dark Blue Sky
Possible Pigments: Lead White, Iron Oxides, Azurite, Calcium Sulphate/Carbonate, Zinc White (Overpaint)
* Lapis Lazuli and Organic Pigments (e.g. Lakes, Dyestuff, etc.) are difficult to detect with XRF