Analytical and Bioanalytical Chemistry

, Volume 397, Issue 2, pp 841–849 | Cite as

Metal oxalates in paints: a Raman investigation on the relative reactivities of different pigments to oxalic acid solutions

  • A. Zoppi
  • C. LofrumentoEmail author
  • N. F. C. Mendes
  • E. M. Castellucci
Original Paper


One degradation phenomenon that occurs in artworks is the formation of metal oxalates on their surfaces. In order to gain insight into the inclination of pigments to produce oxalates, nine pigments including Na, Ca, Fe, Pb and Cu cations were selected to react with oxalic acid solutions at different concentrations (1 M, 0.1 M, 0.01 M and 0.005 M). Micro-Raman spectroscopy was used to detect the different reaction products. Pigments containing calcium (calcite, gypsum and Volterra gypsum) showed a high tendency to form weddellite as well as whewellite, especially at high acidic concentrations; among copper-based pigments (malachite, azurite, verdigris), the formation of moolooite was observed for high concentrations of acid and down to the lowest concentration (0.005 M) in the case of verdigris. Lead oxalate was detected on lead white. No iron oxalates were observed for hematite; the formation of calcium oxalate crystals was observed instead. Ultramarine blue reacted to produce elemental sulfur. According to the results obtained, calcite and verdigris showed the highest reactivity in oxalic acid environments, resulting in a high tendency to form calcium and copper oxalates, even at very low acidic concentrations; this behavior seems to arise from the high solubilities of these pigments in acidic environments.


Moolooite Whewellite Weddellite Oxalates Oxalic acid Micro-Raman 


  1. 1.
    Vandenabeele P, Edwards HGM, Moens L (2007) Chem Rev 107:675–686CrossRefGoogle Scholar
  2. 2.
    Schoukens I, Tourwé E, Guillaume J, Nguyen V, Vereecken J, Terryn H (2008) Surf Interface Anal 40:474–477CrossRefGoogle Scholar
  3. 3.
    Aibéo C, Castellucci EM, Mattini M, Sacchi B, Zoppi A, Lofrumento C (2008) In: Kroustallis S, Townsend JH, Cenalmor Bruquetas E, Stijnman A, San Andrei Moya M (eds) Art technology: sources and methods (Proocedings of the Second Symposium of the Art Technological Source Research Working Group). Archetype, LondonGoogle Scholar
  4. 4.
    Bordignon F, Postorino P, Dore P, Laurenzi-Tabasso M (2008) Stud Conserv 53:1–12Google Scholar
  5. 5.
    Realini M, Toniolo L (1996) The oxalate films in the conservation of works of art: II international symposium (Proceedings: Centro CNR "Gino Bozza" per lo studio delle cause di deperimento e dei metodi di conservazione delle opere d'arte). Politecnico di Milano, MilanGoogle Scholar
  6. 6.
    Alessandrini G (1989) The oxalate films: origin and significance in the conservation of works of art. Centro Congressi Cariplo, MilanGoogle Scholar
  7. 7.
    Droghini F, Giamello M, Guasparri G, Sabatini G, Scala A (2009) Archaeol Anthropol Sci 1:123–136Google Scholar
  8. 8.
    Castro K, Sarmiento A, Martinez-Arkarazo I, Madariaga JM, Fernándes LA (2008) Anal Chem 80:4103–4110CrossRefGoogle Scholar
  9. 9.
    Miliani C, Doherty B, Daveri A, Loesch A, Ulbricht H, Brunetti BG, Sgamellotti A (2009) Spectrochim Acta Part A 73:587–592Google Scholar
  10. 10.
    Mendes N, Lofrumento C, Migliori A, Castellucci EM (2008) J Raman Spectrosc 39:289–294CrossRefGoogle Scholar
  11. 11.
    Castro K, Proietti N, Princi E, Pessanha S, Carvalho ML, Vicini S, Capitani D, Madariaga JM (2008) Anal Chim Acta 623:187–194CrossRefGoogle Scholar
  12. 12.
    Castro K, Sarmiento A, Maguregui M, Martínez-Arkarazo I, Etxebarria N, Angulo M, Urrutikoetxea Barrutia M, González-Cembellín JM, Madariaga JM (2008) Anal Bioanal Chem 392:755–763CrossRefGoogle Scholar
  13. 13.
    Nevin A, Loring Melia J, Osticioli I, Gautier G, Colombini MP (2008) J Cult Herit 9:154–161Google Scholar
  14. 14.
    Sansonetti A, Bugini R, Biondelli D, Striova J, Colella M (2008) Painting layers on stone: study of an Early Middle Ages high-relief. In: Proc 9th Int Conf on NDT of Art, Jerusalem, Israel, 25–30 May 2008 (see
  15. 15.
    Rampazzi L, Andreotti A, Bonaduce I, Colombini MP, Colombo C, Toniolo L (2004) Talanta 63:967–977CrossRefGoogle Scholar
  16. 16.
    Frost RL (2004) Anal Chim Acta 517:207–214CrossRefGoogle Scholar
  17. 17.
    Osticioli I, Mendes NFC, Nevin A, Zoppi A, Lofrumento C, Becucci M, Castellucci EM (2009) Rev Sci Instrum 80:076109Google Scholar
  18. 18.
    Bell IM, Clark RJH, Gibbs PJ (1999) Spectrochim Acta Part A 53:2159–2179Google Scholar
  19. 19.
    Edwards HGM, Farwell DW (1991) Spectrochim Acta Part A 47:1531–1539Google Scholar
  20. 20.
    Švarcová S, Hradil D, Hradilovà J, Kocì E, Bezdicka P (2009) Anal Bioanal Chem 395:2037–2050CrossRefGoogle Scholar
  21. 21.
    Taxiarchou M, Panias D, Douni I, Paspaliaris I, Kontopoulos A (1997) Hydrometallurgy 44:287–299Google Scholar
  22. 22.
    Del Federico E, Shöfberger W, Schelvis J, Kapetanaki (2006) Inorg Chem 45:1270–1276CrossRefGoogle Scholar
  23. 23.
    Frost L, Weier ML (2003) J Raman Spectrosc 34(10):776–785CrossRefGoogle Scholar
  24. 24.
    Kim KM (1996) Scanning Microsc 10(2):445–455Google Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • A. Zoppi
    • 1
  • C. Lofrumento
    • 1
    Email author
  • N. F. C. Mendes
    • 1
  • E. M. Castellucci
    • 1
  1. 1.Dipartimento di Chimica, Polo Scientifico e TecnologicoUniversità di FirenzeFirenzeItaly

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