CrustA visually thick and opaque hard or brittle coating (partially) covering the surface of the paint which is well-adhered to the paint layer.
COMMENT: COMMENT: Crusts are composed of metal carboxylates which have formed within the paint layer(s) and have migrated to the surface where they have reacted with atmospheric pollutants to form a well-adhered, hard layer. They are difficult to remove.
LiteratureBoon J.J., Processes inside paintings that affect the picture: chemical changes at, near and underneath the paint surface, 2006, in: Reporting the highlights of the De Mayerne programme NWO, The Hague, November 2006, pp 21-32
Sawicka A., Burnstock., Izzo F.C., Keune K., Boon J.J., Kirsch K., van den Berg K.J., An investigation into the viability of removal of lead soap efflorescence from contemporary oil paintings, 2014, in: Issues in Contemporary Oil Paint, pp 311-332
Van der Snickt G., Janssens K., Dik J., De Nolf W., Vanmeert F., Jaroszewicz J.,Cotte M., Falkenberg G., Van der Loeff L., Combined use of Synchrotron Radiation Based Micro-X-ray Fluorescence, Micro-X-ray Diffraction, Micro-X-ray Absorption Near-Edge, and Micro-Fourier Transform Infrared Spectroscopies for Revealing an Alternative Degradation Pathway of the Pigment Cadmium Yellow in a Painting by Van Gogh, 2012, in: Analytical Chemisty 2012 vol. 84 (23), pp 10221–10228
Burnstock A., Cross M., Serres K., Insoluble surface spots, metal soaps and challenges in the conservation of Goya’s Portrait of Francisco de Saavedra, 2017, in: Postprints of the ICOM-CC 18th Triennial Conference, Copenhagen, 2017, paper 1301
Surface Whitening(White) Haze