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Seventeenth century

Fabrication and origin of magnetic cannons, White Delft and a shipload of semi-finished articles.

Research applications at the RCE are usually focused on the fabrication or origin of materials or objects. The three applications presented here all fall under the heading of 'materials from the 17th century'.

Lucas van Dijk takes a sample from a bronze cannon.

Lucas van Dijk takes a sample from a bronze cannon in order to examine the microstructure.

Magnetic cannons

Poor quality copper ore had led to local staining on 17th-century bronze cannons. Research into the cause of a rapid discolouration of the canons after cleaning provided the discovery of another interesting phenomenon: magnetism. From then on, this project was carried out from the perspectives of both materials science and history.


The starting point for the research was the cleaning of a number of 17th century bronze cannons cast by Cornelis Ouwerogge. All are from the underwater archaeological collection of the RCE. Very shortly after cleaning the discolouration due to corrosion arose once more. It appeared to be rust: could there be iron in bronze?


That thought proved indeed correct. A magnet was attracted to it and a portable X-ray fluorescence device showed that a small amount of iron was present in the material: unusual for bronze. In order to determine the origin, a small sample was taken from the cannon and further examined in an electron microscope. The iron, which probably came to be in the bronze as an impurity, was in a pure form in very small inclusions. This resulted in both the magnetism and the rapid corrosion.

White Delft

Although blue delft has become the icon of Dutch industry in the 17th and 18th centuries, at that time 'white delft' was produced in much larger quantities:  unpainted white glazed pottery for household use. It is often difficult to determine its origin precisely because it is unpainted. It was investigated whether it would be possible to determine where the objects were made on the basis of the chemical composition of the glaze. In particular, the amounts of lead and tin in the glaze and the proportion between them appeared to be connected to the place of production.


A remarkable aspect of this project is the use of scientific methods in the attribution of faience. The results of the research were reported in the publication accompanying the exhibition Delfts Wit: het is niet alleen blauw dat in Delft blinkt [White Delft - not just blue] in The Hague Municipal Museum from 23 November 2013 to 24 March 2014.

Ship Finds from the Aanloop Molengat

The cargo of the wreck of the Aanloop Molengat, sunk at Texel in the early 17th century, consisted almost entirely of semi-finished products: wrought iron bars, lead ingots, tin sheets, Flemish and Dutch woollen cloth, ivory and cattle hides. The fabrication and origin of the iron were investigated at the RCE using metallography and the analysis of the chemical composition of slag inclusions in the iron. The results provided information on the trade routes in the 17th century.


Virtually all the woollen cloth decayed after the ship sank. What did remain were a hundred or so textile leaden seals that once hung on the lengths of cloth. The stamps on the seals indicate that the cloth came from Leiden and Delft. Two seals bore the stamp of an eagle, a sign that the cloth had been dyed with woad (a plant that produces blue dye). The colour of the only piece of cloth found, a minuscule strip, was examined by high performance liquid chromatography (HPLC). This revealed that the wool was dyed with a mixture of madder and indigo or woad, making it likely that it was coloured brown or purple.