Spectroscopic techniques for the characterization of organic and inorganic materials in modern art:

a case study

Francesca Rosi1, Alessia Daveri1, Costanza Miliani2, Brunetto Giovanni Brunetti1, Antonio Sgamellotti1,2

1Dip. di Chimica, Università di Perugia, Via Elce di Sotto, 8, Perugia, 06123 (PG) - ITALY2Dip. di Chimica, CNR c/o Università di Perugia, Via Elce di Sotto, 8, Perugia, 06123 (PG) - ITALY

Sezione Tematica INSTM: 1. Materiali inorganici cristallini ed amorfi

The study of materials and techniques of contemporary art

the employ of new materials and not well codified techniques having at disposal a large variety of new materials and also the license to use them with

unconventional execution techniques

The intrinsic complexity of modern artworks

The necessity to characterize materials and methods for preserving the conservation state and start correct

conservation procedures

Project PRIN2006: Development of specific methodologies for the non-invasive study of materials and techniques of contemporary art

Calamita Cosmica

enormous sculpture representing a human skeleton dimensions 24x6x10 m3

Gino De Dominicis (1947-1998)

www.repubblica.it

Mole Vanvitelliana, Ancona 2005

Piazzetta Reale, Milano 2007

Micro destructive spectroscopic techniques

Leica DM R Optical Microscope (OM) equipped with a digital camera Leica

DC300

SEM-EDS Electron scanning microscope Philips XL30 with an LaB6source and an energy

dispersive X-ray EDAX/DX4 detector. Epoxy resin (Epofix, Struers) was used for the

preparation of cross-sections

JASCO Ventuno micro-Raman (R):- 1200 and 2400 mm/lines gratings- CCD detector cooled at –50°C; - Confocal OM (5x, 20x, 50x, 100x). - Nd:YAG laser (532 nm); - spectral resolution of about 2 cm-1

JASCO FTIR 470-plus spectrophotometer Micro-FTIR (FTIR):

-nitrogen cooled mercury cadmium telluride detector (MCT)

-IRT-30 optical microscope-reflectance transmittance geometry

(Cassegrain 16x/32x objectives)

Diffuse reflection can cause distortion of the band intensities as compared to transmission spectra, and specular reflection may cause derivative or inverted band shape.

1200 1600 2000 2400 2800 3200 3600 4000

wavelength (m)

absorbance (a.u.)

log

(1/R

) (a

.u.)

wavenumber (cm-1)

11 10 9 8 7 6 5 4 3

1+ 3 1+ 4

3

transmittance

Mapping FTIR measurement

molecular distribution in the stratigraphy 16x Cassegrain objective; map dimension 250x550m2 ;

x,y step 50 m ; total time 13 hScans 800; spectral resolution 4 cm-1

specular0°/0° geometry

Reflectance FTIR technique

diffuse

The enormous sculpture is mainly composed by polystyrene (EPS)Gypsum has been found as filler

Materials characterization

Stratigraphic study

1

2

3

4

5

1. White layer of variable thickness2. light brown layer 260-395 m3. brass lamina 80-230 m4. white layer 100-150 m5. white layer 790-900 m

OM image BSE-SEM image

1 & 2 inner layers

elemental composition: Si, Al, Ca, Fe, Tiinorganic components

CaCO3: 1+3 @ 2500 cm-1; 1+4 @ 1800 cm-1

-SiO2 : (-SiO2) @ 1100 cm-1; + (- SiO2) @ 1800;1870; 1980 cm-1

organic components

3. Brass lamina

Cu, Zn

brass (15% of Zn, similoro brass)

analogies with the gold decoration technique of ancient painters

Benozzo Gozzoli, S.Girolamo Chapel, Montefalco (1452)

Sn

Au

80-230 m

4. white layer

Elemental composition similar to 1 & 2 layers: Si, Al, Ca, Ti,

Mg

1000 1500 3000 3500

absorbance (arbitrary unit)

36

75

10

14

log

1/R

(ar

bitr

ary

unit)

wavenumber / cm-1

talc standard layer 4

17

50Talc is a hydrated magnesium

silicate with the chemical formula Mg3 Si4 O10 (OH)2

Organic molecular patterns with carbonyl

ester @ 1750 cm-1

100-150 m

5. white finish layer

Elemental composition: Si and Ti as main elements

L. Burgio, R. J. H. Clark, Kournal of Raman Spectroscopy, 31, 395–401 (2000)

790-900 m

Micro FT-IR mapping experiments

Area of the 1+3

combination band

@ 2428-2638 cm -1

CaCO3 distribution

CaCO3 is mainly distributed in layers 4, 1 &

2, it is absent in the external white layer

Micro FT-IR mapping experiments

Organic compounds distribution

Shift of the carbonyl stretching from 1730-

1750 cm -1

Micro FT-IR mapping experiments

Polystyrene distribution

2500 3000 3500

log

1/R

(ar

bitrar

y un

it)

wavenumber / cm-1

polystyrene layer 5

CH signal @ 3013-3095 cm -1

1

2

3

4

5

Allumino silicate matrix with CaCO3 , SiO2, TiO2, Fe-oxides; oilresin 1750 cm-1 carbonyl

Cu, Zn lamina

Allumino silicate matrix with CaCO3 , SiO2, TiO2, Fe-oxides, talc; 1750 cm-1

carbonyl

Polystyrene mixed with SiO2, TiO2, talc, ftalo dyes; 1740 cm-1 carbonyl

Stratigraphic study

Calamita CosmicaConservation

polystyrene substrata external painted layers: difference in mechanical properties; salt crystallization; aging of external vinyl resin

www.repubblica.it

NA WD32x 0.7 10mm16x 0.57 20.5mm