Non-destructive Analysis of Historical Paintings with Spatially Resolved XRF

Bruker Nano GmbH, Berlin Webinar, April 30th, 2014

Innovation with Integrity

Presenters

Prof. Dr. Joris Dik

Antoni van Leeuwenhook Chair, Materials in Art and Archeology, Delft University of Technology, The Netherlands

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Dr. Andreas Wittkopp

Business Manager Micro-XRF – EMEA Region, Bruker Nano, Berlin, Germany

Overview

First Part • Requirements for large scale Micro-XRF

• Instrument concept • Technical specifications • Analytical performance • Application example Second Part • Application examples – “Looking through paintings”

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Requirements for large scale Micro-XRF

• Due to its non-destructive property small spot/µ-EDXRF is a well established analytical method used in the cultural heritage community

• Current Micro-XRF instruments typically have a closed sample chamber configuration

Advantages • Enables to operate under vacuum condition and extends elements

range down to Na • Meets condition of a full protection device

Disadvantage • Maximum measurable samples size is dictated by chamber size and

sample positioning device

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Requirements for large scale Micro-XRF

From the cultural heritage science segment however there is the demand to apply Micro-XRF method to larger objects. Based on input from the University of Antwerp and University of Delft a Micro-XRF spectrometer was developed which meets following requirements: • Analysis of large scale areas • Can be positioned in front of the sample. The sample remains fixed,

instead the measurement head device is moving • Entire spectrometer should be transportable • Samples shall be scanned either in horizontal or vertical plane • Scanning in Hypermap mode. This means measurement head moves

continuously up to a maximum speed of 100 mm/s which translates into efficient measure times down to <1 ms/pixel

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M6 JETSTREAM

• Mapping of areas of up to 800 x 600 mm2 (32 x 24 inches)

• Spot size adaptable to structure size in the range of 100–500 µm

• Excellent spatial resolution – measurement file sizes in the megapixel range

• Moving measurement head in front of the stationary sample

• Instrument can be disassembled into four parts for transport

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Flexible and transportable spectrometer

• The M6 JETSTREAM can be disassembled into four parts for easy transport

• The lower part has castors to position the instrument in front of the sample. The system can be immobilized using brakes

• The upper part (measurement rig) can be tilted vertically by ± 10°for fine adjustment to the sample surface

• The rig can be also tilted by 90°into a horizontal position for top-down measurements

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Flexible sample positioning

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On-site measurement of paintings directly on the wall or on an easel

Vertical sample position

On-site measurement of scripts positioned on a table, large geological samples, e.g. drill cores, or industrial samples, e.g. solar cells

Horizontal sample position

Flexible sample positioning

Rig can be tilted by ±10 degrees

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Measurement head

Measurement head with …

• X-ray tube and poly-cap optic for focusing the excitation beam

• High throughput SDD (30 mm², resolution < 145 eV at Mn Kα)

• Two optical microscopes with different magnifications for coarse and fine positioning

• For full sample view video images can be stitched in order to generate a mosaic image

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Variable spot size

In case of mapping large areas or structures which don’t require maximum resolution spot size can be changed without significant loss of excitation intensity by varying the working distance.

• 5 different working distances can be defined by moving the distance below initial focal plane

• Focal plane of the high mag. video microscope can be adjusted accordingly

• Spot size range can be adjusted between 100 and 500 µm.

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Focal plane

Variable spot size

• Working distance with smallest spot size is 5.5 mm

• Variation range of working distance is approx. 13 mm

• 2 optical microscopes with different magnifications for coarse and fine positioning

• Variation of spot size with energy is determined by the energy dependency of the critical angle of total reflection

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Data by M. Alfeld et al. In JAAS, 28, (2013), 760

Analytical performance Sensitivity

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Sensitivity for elements K (Z=19) to Sb (Z=51) at 50 kV, 0.6 mA

LODs for K (Z=19) to Sb (Z=51) at 1s measure time

At 10 ms still LODs in the range of 2000 ppm can be achieved Data by M. Alfeld et al. In JAAS, 28, (2013), 760

Open spectrometer

The M6 JETSTREAM is an open instrument which requires special radiation safety precautions

• The instrument needs to be secured against personal access

• The instrument PC can be installed up to 2 m away from the spectrometer

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Open spectrometer Radiation safety precautions

The M6 JETSTREAM provides following safety conditions: • The X-ray tube only can be switched

on if the shutter is closed.

• Starting the measurement is only possible by a double safety action (opening a lid and pressing a button and start the measurement in the software with another button simultaneously).

• Both status high voltage on (orange) and open shutter (red) are indicated by a special signal light tower.

• The instrument has an EMO button which interrupts power supply of the instrument.

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Technical specifications M6 JETSTREAM

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Parameter Values Travel range (X-Y-Z) 800 x 600 x 90 mm

Travel speed up to 100 mm/s (X-Y), 50 mm/s (Z), minimum step size 10 μm

Spot size adjustable in 5 steps between approx. 100–500 µm using polycapillary optics

Excitation Micro-focus tube (max. 50 kV, 600 µA), Rh-target

Excitation direction perpendicular to sample surface to allow different sample (working) distances

Detection 30 mm² SDD, energy resolution < 145 eV at Mn Kα

Sample view 2 optical microscopes which display sample areas of 30 x 22 mm² and 11 x 8 mm²

Mosaic image Generation of a mosaic image of the complete mapping area both with full resolution and compressed

Measurement modes Point: single point measurements MultiPoint: automatic measurement of point patterns (single

points, lines, matrices) Area: distribution analysis on areas

• Use of 64 bit operating system Windows 7 and at least 8 GB RAM permits generation and storage of multi-megapixel maps of highest resolution, even for large samples

• Optical mosaic acquisition using the instrument's video cameras

• Selection of working distance

• Flexible measurement setup under consideration of object (single spot, line scan or area), step size and dwell time

• Acquisition of measurement data in hyperspectral database files

• Large toolkit for processing hyperspectral databases (HyperMaps), extraction of arbitrary object sum spectra (ellipses, rectangles, polygons)

• Extraction of line scans

• Determination of elements present only at single measurement locations (MaximumPixelSpectrum) chemical phase analysis (Autophase)

• Standardless Fundamental Parameter (FP) quantification

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Powerful Software Package M6 JETSTREAM

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2 optical microscopes allow • The display of an image with the

size of 11 x 8 mm² for the exact determination of the measurement point

• The display of an image with the size of 30 x 22 mm² for a larger overview and

• The generation of a mosaic image composed from single images of larger size The displayed icon in its frame is composed from 14 x 21 large single images and shows an area of 42 x 46 cm²

Example Slavic Icon

Element distribution – HyperMap Slavic Icon – Measurement conditions

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Element distribution measured with • 556 x 632 pixels • a step size of 500 µm • a spot size of 500 µm • a pixel dwell time of 15 ms and • approx. 1 h 50 min. total measurement time All acquisitions are performed as a HyperMap • a complete spectrum is saved for every measurement point • offers a wide variety of data post-processing options

Element distribution – HyperMap Slavic Icon

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Distribution of Ti-K and Ba-L lines without deconvolution

Distribution of Ti-K and Ba-L lines with deconvolution

Deconvolution Slavic Icon

• M6 design is tailored to the specific requirements for elemental mapping of large and valuable objects of cultural heritage

• Maps of areas of up to 800 x 600 mm2 can be executed in one run

• Mapping speed can be up to 100mm/s • Spot size is adaptable to structure size in the

range of 100–500 µm • Excellent spatial resolution – measurement file

sizes can be in the megapixel range. This allows resolution down to 200 µm for maximum mapping area

• Comprehensive data and image processing features enable user to reveal information of interest

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M6 JETSTREAM Summary

Looking through Paintings Joris Dik

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December 17, 2007

December 17, 2007

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Meta Chavannes and Louis van Tilborgh, "A missing Van Gogh unveiled," The Burlington Magazine, August 2007, No. 1253, Vol. CXLIX

Meta Chavannes and Louis van Van Gogh unveiled," The August 2007, No. 1253, Vol. CXLIX

Vincent van Gogh, ‘Ravine’, oil on canvas, 1889 Museum of Fine Arts, Boston

X-ray radiography

Vincent van Gogh, ‘Wild Vegetation’, drawing, 1889 Van Gogh Museum, Amsterdam

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correspondence Van Gogh

drawings

?

hidden paintings

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limitation of X-rays

-> dominance of lead white

V. van Gogh, unfinished portrait, Van Gogh Museum, Amsterdam

Art Institute, Chicago J.F. Bazille, Self-portrait with Palette, Paris, 1865

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conventional X-ray

elements on the painters palette

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Art Institute, Chicago J.F. Bazille, Self-portrait with Palette, Paris, 1865

Vincent van Gogh Patch of Grass

Paris, 1887 Kröller Müller Museum Otterlo, the Netherlands

X-ray radiography

portrait of a woman? Nuenen, 1884/1885?

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cross section

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grass landscape

hidden face

intermediate ground

paint cross-section

SEM/EDS:

Pb, Hg, Sb/Ca?,Fe, Mn, P

SEM/EDS:

Pb, Zn

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Synchrotron-based μ-XRF

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incoming synchrotron X-ray beam

fluorescence detector

Karen Rickers at Beamline L, DORIS III, DESY

XRF scanning parameters

- 300x300 pixel square - 40keV monochromatic (SbK)

- 0,1mm beam footprint - 0,5mm step size - 2s/pixel dwell time - total acquisition time approximately 50 hours

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SbK PbL BaK ZnK

Zn, Ba

Pb

Sb, Hg

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cinnabar (Hg)

lead antimonate yellow (Sb)

the color reconstruction

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public profile ...

J. Dik, K. Janssens, G. van der Snickt, L. van der Loeff, K. Rickers, M. Cotte, Analytical Chemistry, 2008, 80, 6436-6442

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Vincent van Gogh (?), Flower Still Life, Kröller Müller Museum, Otterlo, inv. nr. KM 100.067, 100 x 80 cm, KMcat.pag.155., afb pag. 156 17

ZnK detected @ back side 18

I’ve been dreadfully busy this week because, as well as the painting class, I also go drawing in the evenings, and then after that go on and work from a model at a club from half past 9 to half past 11. For I’ve become a member of no fewer than two of these clubs. And I now know two fellows who to my mind draw well, both Dutch. This week I painted a large thing with two nude torsos — two wrestlers, a pose set by Verlat. And I really like doing that.

letter 555 from Vincent van Gogh to Theo van Gogh Antwerp, on or about Thursday, 28 January 1886

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from synchrotron science ... (2008)

... to mobile applications (2012)

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Rembrandt and/or studio, The Syndics,1662, canvas, 190.5 x 280.5 cm, Rijksmuseum

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Pb-L - lead white

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Vincent van Gogh, Flowers in a Blue Vase, 1889

Rijksmuseum Kröller-Müller, Otterlo, the Netherlands

Vincent van Gogh, Flowers in a Blue Vase, 1889

Rijksmuseum Kröller-Müller, Otterlo, the Netherlands

Cadmium yellow (CdS) degradation

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December 17, 2007 4

Vincent van Gogh, Flowers in a Blue Vase, 1889 Rijksmuseum Kroeller-Mueller, Otterlo

Cadmium yellow underneath degradation crust

1. G Van der Snickt et al, Anal. Chem., 2009, 81, 2600 (DOI: 10.1021/ac802518z) 2. G Van der Snickt et al, Anal. Chem., 2012, DOI: 10.1021/ac3015627

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Cd-K

visual photograph XRF distribution of cadmium (Cd)

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digital reconstruction of potential original appearance

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Cd-K

XRF distribution of cadmium (Cd)

visual photograph

Getty Museum Los Angeles

Rijksmuseum Amsterdam

Mauritshuis Den Haag The Art Institute

Chicago

National Gallery Washington, DC

National Portrait Gallery London

Metropolitan Museum of Art New York

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December 17, 2007

Vermelding onderdeel organisatie

Acknowledgements Dr. Michael Haschke Dr. Roald Tagle Ulrich Waldschläger … and all others involved in developing and building the M6 JETSTREAM

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December 17, 2007

Vermelding onderdeel organisatie

Acknowledgements

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• Koen Janssens (UA, Antwerp) • Luuk van der Loeff (Kroller Muller Museum, Otterlo,

Holland) • Wolfgang Drube, Thomas Wroblewski, Edgar Weckert

(DESY, Hamburg) • Jean Susini, Alberto Bravin, Christian Nemoz, Lukas Helfen,

Peter Reischig (ESRF, Grenoble) • Ella Hendriks (Van Gogh Museum, Amsterdam) • Ernst van de Wetering (Rembrandt Research Project,

Amsterdam) • Andrea Sartorius, Mark Leonard, (J. Paul Getty Museum) • Carole Namowicz, Marc Walton, Karen Trentelman,

Giacomo Chiari (Getty Conservation Institute) • Jorik Blaas, Charl Botha, Kris Krug (TU Delft)

Innovational Research Incentives Scheme (IRIS), The Netherlands Organization for Scientific Research Center for Art and Archaeological Sciences (CAAS), Leiden University and Delft University of Technology

financed by

Innovation with Integrity

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