Toward a Complete Molecular Model for the Formation of Metal Soaps in Oil Paints

  • Joen J. HermansEmail author
  • Katrien Keune
  • Annelies Van Loon
  • Piet D. Iedema
Part of the Cultural Heritage Science book series (CUHESC)


An overview is presented of the current state of understanding of the chemical pathways that lead to the formation of crystalline metal soap phases in oil paints, based on recent experimental work by the authors and supported by relevant literature. Improved (quantitative) interpretation of Fourier-transform infrared (FTIR) spectra has revealed that metal ions are bound to carboxylate functionalities of the oil polymer during oil paint aging, a state similar to ionomeric polymers. Tailored ionomer-like systems based on linseed oil were synthesized to study the structure of the mature oil paint binding medium, and such systems were used as the starting point for studies on metal soap crystallization. Additionally, series of differential scanning calorimetry (DSC) studies shed light on the driving forces and kinetics of metal soap crystallization, and electron microscopy studies have been used to image the initial stages of metal soap crystallization. The results have been used to construct a model of the chemical reactions leading to metal soaps from a mixture of pigment and oil. Additionally, the model provides insight into diffusion mechanisms for metal ions and fatty acids and potential physical transitions in the structure of metal soaps. The mechanisms described are helpful in explaining the different morphologies of lead and zinc soaps observed in actual samples from historic paintings and the locations within paint films where these are typically found.



The authors are indebted to Dr. John Drennan and his co-workers at the Australian Microscopy and Microanalysis Research Facility (AMMRF) for the collaborative effort to visualize the early stages of zinc soap crystallization. Lambert Baij, Robert Corkery, Ties Korstanje, and Silvia Centeno are thanked for sharing their knowledge and inspiring discussions.


  1. 1.
    Badre C, Dubot P, Lincot D, Pauporte T, Turmine M (2007) Effects of nanorod structure and conformation of fatty acid self-assembled layers on superhydrophobicity of zinc oxide surface. J Colloid Interface Sci 316(2):233–237Google Scholar
  2. 2.
    Boon JJ, Hoogland FG (2014) Investigating fluidizing dripping pink commercial paint on van Hemert’s seven-series works from 1990–1995. In: van den Berg KJ, Burnstock A, de Keijzer M, Krueger J, Learner T, Tagle A de, Heydenreich G (eds) Issues in contemporary oil paint. Springer, Cham, pp 227–246Google Scholar
  3. 3.
    Boon JJ, Hoogland F, Keune K (2006) Chemical processes in aged oil paints affecting metal soap migration and aggregation. In: AIC annual meeting, Providence, pp 18–25Google Scholar
  4. 4.
    Castagna AM, Wang W, Winey KI, Runt J (2011) Structure and dynamics of zinc-neutralized sulfonated polystyrene ionomers. Macromolecules 44:2791–2798CrossRefGoogle Scholar
  5. 5.
    Cesarano J, Aksay IA (1988) Processing of highly concentrated aqueous α-alumina suspensions stabilized with polyelectrolytes. J Am Ceram Soc 71(12):1062–1067CrossRefGoogle Scholar
  6. 6.
    Clementi C, Rosi F, Romani A, Vivani R, Brunetti BG, Miliani C (2012) Photoluminescence properties of zinc oxide in paints: a study of the effect of self-absorption and passivation. Appl Spectrosc 66(10):1233–1241CrossRefGoogle Scholar
  7. 7.
    Fragiadakis D, Dou S, Colby RH, Runt J (2008) Molecular mobility, ion mobility, and mobile ion concentration in poly(ethylene oxide)-based polyurethane ionomers. Macromolecules 41:5723–5728CrossRefGoogle Scholar
  8. 8.
    Gabrieli F, Rosi F, Vichi A, Cartechini L, Pensabene Buemi L, Kazarian SG, Miliani C (2017) Revealing the nature and distribution of metal carboxylates in Jackson Pollock’s Alchemy (1947) by micro-attenuated total reflection FT-IR spectroscopic imaging. Anal Chem 89(2):1283–1289CrossRefGoogle Scholar
  9. 9.
    Hall LM, Stevens MJ, Frischknecht AL (2012) Dynamics of model ionomer melts of various architectures. Macromolecules 45:8097–8108CrossRefGoogle Scholar
  10. 10.
    Helwig K, Poulin J, Corbeil MC, Moffatt E, Duguay D (2014) Conservation issues in several twentieth-century Canadian oil paintings: the role of zinc carboxylate reaction products. In: van den Berg KJ (ed) Issues in contemporary oil paint. Springer, Cham, pp 167–184Google Scholar
  11. 11.
    Hermans JJ (2017) Metal soaps in oil paint: structure, mechanisms and dynamics. Ph.D. thesis, University of AmsterdamGoogle Scholar
  12. 12.
    Hermans JJ, Keune K, van Loon A, Corkery RW, Iedema PD (2014) The molecular structure of three types of long-chain zinc(II) alkanoates for the study of oil paint degradation. Polyhedron 81:335–340CrossRefGoogle Scholar
  13. 13.
    Hermans JJ, Keune K, van Loon A, Iedema PD (2015) An infrared spectroscopic study of the nature of zinc carboxylates in oil paintings. J Anal At Spectrom 30:1600–1608CrossRefGoogle Scholar
  14. 14.
    Hermans JJ, Keune K, van Loon A, Iedema PD (2016a) Ionomer-like structure in mature oil paint binding media. RSC Adv 6:93,363–93,369CrossRefGoogle Scholar
  15. 15.
    Hermans JJ, Keune K, van Loon A, Iedema PD (2016b) The crystallization of metal soaps and fatty acids in oil paint model systems. Phys Chem Chem Phys 18:10896–10905CrossRefGoogle Scholar
  16. 16.
    Higgitt CL, Spring M, Saunders DR (2003) Pigment-medium interactions in oil paint films containing red lead or lead-tin yellow. Nat Gallery Tech Bull 24:75–95Google Scholar
  17. 17.
    Ishioka T, Maeda K, Watanabe I, Kawauchi S, Harada M (2000) Infrared and XAFS study on structure and transition behavior of zinc stearate. Spectrochim Acta A 56:1731–1737CrossRefGoogle Scholar
  18. 18.
    Iwasaki T, Maegawa Y, Hayashi Y, Ohshima T, Mashima K (2008) Transesterification of various methyl esters under mild conditions catalyzed by tetranuclear zinc cluster. J Org Chem 73:5147–5150CrossRefGoogle Scholar
  19. 19.
    Keune K, Boevé-Jones G (2014) It’s surreal: zinc oxide degradation and misperceptions in Salvador Dalí’s couple with clouds in their heads, 1936. In: van den Berg K (ed) Issues in contemporary oil paint. Springer, Cham, pp 283–294Google Scholar
  20. 20.
    Keune K, van Loon A, Boon JJ (2011) SEM backscattered-electron images of paint cross sections as information source for the presence of the lead white pigment and lead-related degradation and migration phenomena in oil paintings. Microsc Microanal 17:696–701CrossRefGoogle Scholar
  21. 21.
    Kutsumizu S, Hashimoto Y, Hirasawal E, Yanot S (1994) dc conduction properties of a model ethylene-methacrylic acid ionomer. Macromolecules 27:1781–1787CrossRefGoogle Scholar
  22. 22.
    Lin KJ, Maranas JK (2012) Cation coordination and motion in a poly(ethylene oxide)-based single ion conductor. Macromolecules 45:6230–6240CrossRefGoogle Scholar
  23. 23.
    Lin CL, Lee CF, Chiu WY (2005) Preparation and properties of poly(acrylic acid) oligomer stabilized superparamagnetic ferrofluid. J Colloid Interface Sci 291(2):411–420CrossRefGoogle Scholar
  24. 24.
    MacDonald MG, Palmer MR, Suchomel MR, Berrie BH (2016) Reaction of Pb(II) and Zn(II) with ethyl linoleate to form structured hybrid inorganic-organic complexes: a model for degradation in historic paint films. ACS Omega 1(3):344–350CrossRefGoogle Scholar
  25. 25.
    Mallégol J, Gardette JL, Lemaire J (1999) Long-term behavior of oil-based varnishes and paints I. Spectroscopic analysis of curing drying oils. J Am Oil Chem Soc 76(8):967–976CrossRefGoogle Scholar
  26. 26.
    Mallégol J, Gardette JL, Lemaire J (2000a) Long-term behavior of oil-based varnishes and paints. Fate of hydroperoxides in drying oils. J Am Oil Chem Soc 77(3):249–255CrossRefGoogle Scholar
  27. 27.
    Mallégol J, Gardette JL, Lemaire J (2000b) Long-term behavior of oil-based varnishes and paints. Photo- and thermooxidation of cured linseed oil. J Am Oil Chem Soc 77:257–263CrossRefGoogle Scholar
  28. 28.
    Mallégol J, Lemaire J, Gardette JL (2000c) Drier influence on the curing of linseed oil. Prog Org Coat 39(2–4):107–113CrossRefGoogle Scholar
  29. 29.
    Mallégol J, Gonon L, Lemaire J, Gardette JL (2001) Long-term behaviour of oil-based varnishes and paints 4. Influence of film thickness on the photooxidation. Polym Degrad Stab 72:191–197CrossRefGoogle Scholar
  30. 30.
    Monico L, Janssens K, Cotte M, Sorace L, Vanmeert F, Brunetti BG, Miliani C (2016) Chromium speciation methods and infrared spectroscopy for studying the chemical reactivity of lead chromate-based pigments in oil medium. Microchem J 124:272–282CrossRefGoogle Scholar
  31. 31.
    Osmond G, Boon JJ, Puskar L, Drennan J (2012) Metal stearate disributions in modern artists’ oil paints: surface and cross-sectional investigation of reference paint films using conventional and synchrotron infrared microspectroscopy. Appl Spectrosc 66(10):1136–1144CrossRefGoogle Scholar
  32. 32.
    Phenix A (2009) Thermal mechanical transitions in artists’ oil paints and selected conservation materials: a study by dynamic mechanical analysis (DMA). In: AIC paintings specialty group postprints, vol 22, pp 72–89Google Scholar
  33. 33.
    Plater M, De Silva B, Gelbrich T, Hursthouse MB, Higgitt CL, Saunders DR (2003) The characterisation of lead fatty acid soaps in ‘protrusions’ in aged traditional oil paint. Polyhedron 22:3171–3179CrossRefGoogle Scholar
  34. 34.
    Sehmi SK, Noimark S, Pike SD, Bear JC, Peveler WJ, Williams CK, Shaffer MSP, Allan E, Parkin IP, MacRobert AJ (2016) Enhancing the antibacterial activity of light-activated surfaces containing crystal violet and ZnO nanoparticles: investigation of nanoparticle size, capping ligand, and dopants. ACS Omega 1(3):334–343CrossRefGoogle Scholar
  35. 35.
    Shen L, Laibinis PE, Hatton TA (1999) Bilayer surfactant stabilized magnetic fluids: synthesis and interactions at interfaces. Langmuir 15(2):447–453CrossRefGoogle Scholar
  36. 36.
    Taheri P, Ghaffari M, Flores JR, Hannour F, De Wit JHW, Mol JMC, Terryn H (2013) Bonding mechanisms at buried interfaces between carboxylic polymers and treated zinc surfaces. J Phys Chem C 117:2780–2792CrossRefGoogle Scholar
  37. 37.
    Thoury M, van Loon A, Keune K, Réfrégiers M, Hermans JJ, Berrie BH (2017, in preparation) Visualization of different phases in the development of metal soaps using synchrotron photoluminescence micro-imaging. In: Metal soaps in art. SpringerGoogle Scholar
  38. 38.
    Tudryn GJ, O’Reilly MV, Dou S, King DR, Winey KI, Runt J, Colby RH (2012) Molecular mobility and cation conduction in polyether-ester-sulfonate copolymer ionomers. Macromolecules 45:3962–3973CrossRefGoogle Scholar
  39. 39.
    Tumosa CS, Erhardt D, Mecklenburg MF, Su X (2005) Linseed oil paint as ionomer: synthesis and characterization. In: Materials research society symposium proceedings, vol 852, pp 25–31Google Scholar
  40. 40.
    van den Berg JDJ, van den Berg KJ, Boon JJ (2001) Determination of the degree of hydrolysis of oil paint samples using a two-step derivatisation method and on-column GC/MS. Prog Org Coat 41:143–155CrossRefGoogle Scholar
  41. 41.
    van den Berg JDJ, Vermist ND, Carlyle L, Holčapek M, Boon JJ (2004) Effects of traditional processing methods of linseed oil on the composition of its triacylglycerols. J Sep Sci 27:181–199CrossRefGoogle Scholar
  42. 42.
    van der Weerd J, van Loon A, Boon JJ (2005) FTIR studies of the effects of pigments on the aging of oil. Stud Conserv 50(1):3–22CrossRefGoogle Scholar

Copyright information

© Crown 2019

Authors and Affiliations

  • Joen J. Hermans
    • 1
    Email author
  • Katrien Keune
    • 2
  • Annelies Van Loon
    • 3
  • Piet D. Iedema
    • 1
  1. 1.Van’t Hoff Institute for Molecular SciencesUniversity of AmsterdamAmsterdamThe Netherlands
  2. 2.Conservation Department, Rijksmuseum, Van’t Hoff Institute for Molecular SciencesUniversity of AmsterdamAmsterdamThe Netherlands
  3. 3.Conservation Department, RijksmuseumAmsterdamThe Netherlands

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