60000

50000

40000

30000

20000

10000

0

500 1000 1500 2000Wavenumber(cm-1)

Inte

nsit

y (a

.u.)

V1 V2 V3SiO2 61.11 57.07 53.10 CaO 18.50 18.64 17.53 MgO 3.82 3.57 3.24 K2O 12.29 16.74 23.49 P2O5 1.67 1.62 1.52 Na2O 0.38 0.67 0.26 Al2O3 1.99 1.38 0.73 TiO2 0.09 0.06 0.03

MnO 0.03 0.02 0.02 Fe2O3 0.15 0.22 0.09

AGING OF MEDIEVAL-LIKE MODEL GLASSAGING OF MEDIEVAL-LIKE MODEL GLASSL. DE FERRI1, D. BERSANI2, Ph. COLOMBAN3, P.P. LOTTICI2,

G. SIMON3, G. VEZZALINI1

1Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia, 41121 Modena, Italylavinia.deferri@unimore.it

2Dipartimento di Fisica, Università di Parma, 43124 Parma, Italy3UPMC Université Paris 06, UMR 7075, Laboratoire de Dynamique, Interactions et

Réactivité (LADIR), F-75005, Paris, France IntroductionIntroduction

Ash-based glass (potash-lime-silica, PLS glass), where K is the main fluxing agent and Ca the main stabilizer, is typical of the cathedral medieval windows in Northern Europe since 1000 A.D. [1,2]. It is very sensitive to alteration phenomena due to the attack of atmospheric pollutants conveyed by water [3,4]. In the alteration process the former leaching step gives a de-alkalinized layer, enriched in silica and H +, then the dissolution of the silica network may occur through an hydrolysis reaction due to the pH increase of the water film. Weathering crystalline products can be identified on the surface after the water evaporation. Three glass samples, representative of the PLS medieval glass, with about 12, 17 and 23% of K2O in V1, V2 and V3, samples, respectively [5] were prepared.Aim of this work is the determination of the influence of K amount on the glass alteration degree.

Chemical compositionChemical composition

Sample cm-1

V1 774V2 767V3 756Sample cm-1

V2 1004V3 1051

Sample cm-1 V1 874V2 884V3 893

FT-IR ATRFT-IR ATR RamanRaman

Raman spectra analyzed on the basis of the Qn model [6]

V1

Q1 and Q2 configurations increase at the expense of Q3 and Q4 with increasing K content

Ip is nearly equal in the three samples ~ 0.3

Greater effect of the melting temperature than the K content

References

Aging experiments: HAging experiments: H22OO attackattackBidistilled water in autoclave: 300°C 80 bars

V1-V2 = 2 weeksV3 = 1 week

With increasing K content

Stained glass windows from the St. Denis Abbey in Paris (details)

Weakening of the Si-O bonds Network depolymerization

ConclusionsConclusions In both acid and water aged glass the alteration degree is directly dependent on the glass K content. The alteration rate (modifier ions release, thickening of alteration layer, weight loss) is higher for K-based glass than Na-based ones [7]Studies on medieval glasses artificially aged following similar procedures in H2SO4 found an average alteration rate of 70 μm/h for potassium-based samples [8]: in our case for V2 the alteration rate appears quite constant during the exchange and lower than the literature values. On the other hand, V3 samples show higher alteration rates confirming the degradation dependence on the glass composition. In the acid attacked glass, crystallization of gypsum and bassanite is observed, while in water attacked glass gyrolite is found.

Glass characterizationGlass characterization

Ca-sulphates crystals aggregate

Aging experiments: HAging experiments: H22SOSO44 ion exchange ion exchange In boiling concentrated sulfuric acid (from an hour to two weeks)

After 6h exposure V3 sample was completely

altered

V3-300 min

750 μm

V3-360 min

120 μm

V3-60 min

Ca-Sulphates (gypsum +

bassanite) were identified as

alteration products

AAS analysis of H2SO4: K release increases with the glass K content .

Raman linear map on the V3-180 min cross section

K release increases with the glass K content.The pH increase causes the breakdown of the network forming Si-O bonds and the glass dissolution The alteration rate increases with the glass K-content increases

Increase of Ip value in aged glass [6].During aging the less bound tetrahedra (Q0 and Q1) are released together with the modifier ions.The area of the stretching band decreases giving higher Ip value. The increase of polymerization is only apparent.

Ip = 0.6

Points of the V2-H2O Raman map

Wavenumber (cm-1)

Inte

nsity

(a.

u.)

[1] O. Schalm, K. Janssens, H. Wouters, D. Caluwé, Composition of 12–18th century window glass in Belgium: Non-figurative windows in secular buildings and stained-glass windows in religious buildings,Spectrochimica Acta Part B 62 (2007) 663–668[2] O. Schalm, I. De Raedt, J. Caen, K. Janssens, A methodology for the identification of glass panes of different origin in a single stained glass window: Application on two 13th century windows, J. Cult. Herit. 11 (2010) 487–492[3] M. Melcher, M. Schreiner, Leaching studies on naturally weathered potash-lime-silica glasses, J. Non-Cryst. Solids 352 (2006), 368-379[4] M. Melcher, R. Wiesinger, M. Schreiner, Degradation of glass artifacts: application of modern surface analytical techniques, Acc. Chem. Res. 43 (2010) 916-926[5] L. De Ferri, D. Bersani, A. Lorenzi, P.P. Lottici, A. Montenero, S. Quartieri, G. Vezzalini, Conservazione e restauro di vetrate antiche: dati preliminari sulla riproduzione di vetri medievali, Proceedings VI National Congress of Archaeometry (Aiar)–Scienza e Beni culturali, Pavia, 2010 February 15-18, accepted.[6] Ph. Colomban, M.P. Etcheverry, M. Asquier, M. Bounichou, A. Tournié, Raman identification of ancient stained glass and their degree of deterioration, J. Raman Spectrosc. Vol. 37 (2006) 614-626[7] J. Sterpenich, G. Liburel, Using stained glass windows to understand the durability of toxic waste matrices, Chem. Geol. 174 (2001) 181.193[8] A. Tournié, P. Ricciardi, Ph. Colomban, Glass corrosion mechanism: a multiscale analysis, Solid State Ionics 179 (2006) 2142-2154

The alteration rate for V2 after 4 hours aging is nearly constant at ~ 21 μm/hThe alteration rate for V3 gradually increases for the first 3 hours up to ~ 227 μm/h

Time (s ½ ) Time (s ½ )Time (s ½ )

Sample Alteration layer thickness (μm)

Alteration rate (μm/h)

Glass weight loss (%)

Extracted K2O (%)

Final water pH

V1 357 1.06 53 3.8 10.0V2 586 1.74 58 9.0 10.1V3 523 3.11 67 13.6 10.7