Andreia Machado (1), Pedro Redol (2,3), Luis Branco (4), Márcia Vilarigues* (1,2)

(1)Department of Conservation and Restoration FCT/UNL, FCT-UNL, Campus de Caparica, 2829-516 Caparica, Portugal, e-mail: machado_andreia@sapo.pt(2)Research Unit “Glass and Ceramic for the Arts”, FCT-UNL, Campus de Caparica, 2829-516 Caparica, Portugal, e-mail: mgv@fct.unl.pt

(3) Monastery of Santa Maria da Vitória, 2440-109 Batalha, Portugal, e-mail: pedro.redol@gmail.com(4) REQUIMTE, CQFB, Department of Chemistry, FCT-UNL, Campus de Caparica, 2829-516 Caparica, Portugal, e-mail: lbranco@dq.fct.unl.pt

“Figura aureolada” - XVth century stained glass panel from the

Monastery of Batalha(REDOL, 2003).

Medieval stained glass production in Portugal begins in the 15th century, late in the european context. The oldest conserved remainscome from the Monastery of Santa Maria da Vitória, in Batalha. The stained glass panel “Figura Aureolada” dates from 1440-1448 andwas originaly installed in the south aisle of the monastery church. Its condition is bad/fragile, presenting, among several otherphenomenas, corrosion crusts, fractures and browning of the surface [1].

Medieval stained glass is characterized by a high amount of alcali and alcali-earth ions, mainly potassium, and low contents ofsilica. In the presence of water and an environment with pH>9, begins the extraction of the alcali ions from the glass network, withthe formation of a hydrated surface layer rich in silica. In the presence of pollutant agents, CO2 and SO2, insoluble salts as calciumcarbonate and calcium sulfate are formed [2].

Nowadays the methods for the cleaning of corrosion crusts tend to be agressive, whether with the aid of scalpels or the applicationof chelant agens such as EDTA, oxalic or citric acids, or the piranha solution, a mixture of sulfuric acid and hidrogen peroxide[3].

Ionic liquids are formed by a combination of an organic cation and an anion (organic or inorganic) with a melting point below of100ºC. The main advantages for this work are related with their low vapor pressure and low volatility, variable solubility and viscosityrates, depending on which cation and anion selected. Additionally many of these materials can be liquids at room temperature, socalled RTIL‟S (Room-Temperature Ionic Liquids)[4].

The experimental studies included: a) Characterization of the detected corrosion at the glass surface, b) selection of seven ionicliquids for dissolution tests of calcium salts and their possible effect on glass and grisaille models of similar composition found inBatalha, and c) cleaning of glass samples that were corroded in laboratory.

The RTIL‟s selected were chosen among three families of cations (ammonium, phosphonium and imidazolium), combined withseveral anions (e.g. chloride, ethylsulfate and dicyanamide). The analytical techniques used were: Optical Microscopy (OM),Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (XRF), Fourier Transform Infrared Spectroscopy(FTIR), Raman spectroscopy and Inductively coupled plasma atomic emission spectroscopy (ICP-AES).

The characterization of a XVth century stained glass panel from the Monastery of Santa Maria da Vitória in Batalha is performed. With the identification of the corrosion products, it is proposed a study of ionic liquids as a cleaning method for the corrosion crusts.

4000 3500 3000 2500 2000 1500 1000 500

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

353

6,6

66

339

8,0

14

163

7,2

95

161

9,9

39

138

6,5

19

131

6,2

36

111

6,6

01

679

,189

Ab

so

rba

nce

wavenumber (cm-1)

599

,763

1

136

5,1

192

2 4 6 8 10 12 14 16 18 20

0

2500

5000

7500

10000

12500

15000

17500

20000

Inte

nsity

KeV

Ca

Ca

BaK Mn

Fe

Fe Cu

Zn

Pb

Zn

Pb

Pb

Rb SrPb

Si

The characterization of the corrosion crusts was performed by non-destructive analysis, with the

identification of white opaque crystalline forms of great adhesion to the surface, constituted mainly of calcium

carbonate, calcium sulfate and calcium oxalate.

Introduction

Experimental Procedure

Ammonium Phosphonium Imidazolium Chloride Ethylsulfate Dicyanamide

FTIR and Raman characterization of ionic liquids show their ability on the dissolution of calcium salts.

3200 3000 2800 2600 2400 2200 2000

200

300

400

500

600

2932,3

4

2901,9

72873,6

22852,9

3

21

88

,59

Inte

nsid

ad

e

2000 1800 1600 1400 1200 1000

14

39

,97

13

06

,64

10

84

,43

n؛ onda (cm-1)

1000 800 600 400 200

71

1,2

71

66

2,9

97

27

9,1

08

17

5,6

64

CaCO3

4000 3000 2000 1000

0,0

0,2

0,4

0,6

0,8

1,0

29

57

,59

29

19

,76

28

58

,11

22

31

,82

2193,9

21

28

,14

14

64

,03

13

72

,96

Ab

so

rsa

nce

wavenumber (cm-1)

33

94

,73

13

12

,71

No significant effects on the glass surface after the application of each ionic liquid were reported. Cleaning tests over corroded glass samples revealed good results.

Results and Disussion

Before After Before After

Application of [P6,6,6,14][DCA] over glass models, on the right, and corroded samples, on the left.

[1] Redol, P., O Mosteiro da Batalha e o Vitral em Portugal nos Séculos XV e XVI, Câmara Municipalda Batalha, Batalha (2003).[2] Tournié, A., Ricciardi, P., Colomban, Ph., „Glass corrosion mehcanisms: A multiscale analysis’,Solid State Ionics 179 (2008)2142-2154.[3] Altavilla, C., Ciliberto, E., La Delfa, S., Panarello, S., Scandurra, A., „The cleaning of early glasses:investigation about the reactivity of different chemical treatments on the surface of ancient glasses‟,Applied Physic A 92 (2008)251-255.[4] Kulkarni, P. S., Branco, L. C., Crespo, J. G., Nunes, M. C., Raymundo, A., Afonso, C. A. M.,„Comparison of Physicochemical Properties of New Ionic Liquids Based on Imidazolium, QuaternaryAmmonium, and Guanidium Cations‟, Chemistry A European Journal 13 (2207)8478-8488.

References

The authors wish to thank Prof. Rui Silva from the Departmentof Material Engineering for the support in the optical microscope.

Acknowledgements

Ionic liquids can be used as alternative greener solvents over the conventional toxic cleaning solvents, because their very low vapor pressure and alsoas designer solvents. Preliminary results have shown a relevant cleaning performance, with a significant controlled removal of the corrosion layer at thesurface. A more detailed analysis of glass models and corroded samples with SEM is in progress. The application of each ionic liquid over the grisailles isbeing performed. After these experiments the application of RTIL‟s will be tested over the stained glass panel of the Monastery of Batalha, named “FiguraAureolada”.

Medieval Stained Glass Cleaning with Ionic Liquids