The blackening of porcelain enamel glazes in anaerobic burial conditions, with particular reference to items from the Geldermalsen shipwreck

This project concerns the intriguing occurrence of blackened lead-glaze enamels on Chinese porcelain, specifically from the Dutch ship ‘Geldermalsen’ which sank in the S. China sea while transporting its cargo to the Netherlands in 1752. The research involves a combination historical documentary research with conservation science and technical art history in order to elucidate the cause of the (sometimes variable) blackening of the decoration of a number of the items recovered from the wreck site. This porcelain enamel blackening is closely related to the anaerobic microbiological blacking of Dutch ‘Delftware’ glazes which has been previously studied by project team members. The project will build on a recent UvA Master thesis investigation in order to provide the first concerted research programme for this phenomenon.

An extensive range of analytical techniques (XRF, SEM-EDS, XRD, LA-ICP-MS, XPS) will be employed to elucidate the chemistry and morphology of the enamels before and after transformation. Experimentation will involve the reconstruction of Chinese enamel recipes together with modelling and reconstruction of the micro-biological deterioration process in the laboratory. The potential for recuperation of the original glaze colours will be explored by means of exposure to UV and high temperature.

The research team comprises not only of Dutch experts with the relevant expertise and analytical instrumentation but also international authorities who can extend the scope of Dutch heritage science organisations with cutting-edge instrumentation and investigative methodologies. Furthermore, there is the potential for innovative technology transfer within and beyond heritage science



  1. 18th century Chinese Famille Verte cup and saucer excavated from the Geldermalsen.
  2. Detail of enamel decoration of pine needles showing selective blackening on the saucer from the Geldermalsen.
  3. 18th century Chinese Famille Rose plates. The one on the left is from the Geldermalsen shipwreck, and the one the right from a private collection with no excavation history.

Images made by Owen Ooievaar