Remanence acquisition in a Roman-style gold furnace

Abstract

In the archaeological site of Magdalensberg, a test furnace (for various experiments) was constructed using similar materials and techniques as during the Roman period. Samples were taken in order to investigate the spatial distribution of magnetic parameters in the floor-bricks after firing at 1300 °C. Twenty samples (40 specimens) were obtained from a brick which was situated almost in the centre of the fired area. The natural remanent magnetization as well as the magnetic susceptibility was measured. Plots (2D) of these values indicate lateral and vertical variations and pin-point the area in the upper part of the brick where the most intense heating took place during the experiment. Specimens from the lower part do not seem to be significantly affected by the heating. Magnetic cleaning (thermal demagnetization) of all specimens revealed the presence of two distinct components of magnetization. Pilot samples were used for the determination of the “palaeo”- intensity using the Thellier method. Although intensity and susceptibility values show remarkable differences between the upper and the lower part of the brick, the TRM effect of the fire is significant up to 5 cm depth. On the other hand, the lateral variation indicates a limitation of the fire effect at a distance of 8–10 cm.