The paint layers are complex assemblies of strata of humidity-sensitive materials which have – over centuries – aged, cracked and delaminated. Cracks join up into the network – the craquelure pattern (CP) – which is a distinctive characteristic of materials and physical structures of the artwork, an outcome of the construction and painting techniques employed.

The research in CRAQUELURE project has four specific objectives:

  • building a database of material properties, including fracture toughness and specific fracture energy, for historical artistic materials used in paintings,
  • developing a comprehensive three-dimensional mechanical model of the paint layer, especially understanding mechanisms and processes involved in CP formation,
  • coupling characteristics of CPs to geographical area and period in which the specific group of paintings was created with a long-term objective also to support authentication of paintings,
  • determining vulnerability of historical paint layers with developed CPs to relative humidity variations – also after conservation treatments –  and elaborating tools supporting the quantitative assessment of risk to paintings which take into account the effect of existing craquelure systems on further propagation of damage.

As part of the project, we have established a long-term collaboration with Patrick Kékicheff, Research Director at the Institut Charles Sadron, University of Strasbourg. Thanks to his scientific experience in imaging techniques, including x-ray microtomography (micro-CT), we can study the structure of cracks in individual layers of the sample with an accuracy of micrometres. Initial research was carried out on a sample of a 17th-century Flemish painting on a board and a 19th-century decorated wood from antependium. The obtained results allow us to clearly determine the location and nature of the cracks. As part of further cooperation, we also plan measurements at the SOLEIL synchrotron in France.

X-ray microtomography enabled observation in 3D of cracks on the surface as well as in cross-section of the oil painting on the board. The study was performed by P. Kékicheff, Research Director at the Institut Charles Sadron (France)