Manufacture
The Berlin Gold Hat is made of a gold alloy of 87.7% Au, 9.8% Ag, 0.4% Cu and 0.1% Sn. It is hammered seamlessly from a single piece. The amount of gold used would form a cube of only 3 cm dimensions. The average thickness is 0.6 mm.
Because of the tribological characteristics of the material, it tends to harden with increasing deformation (see ductility), increasing its potential to crack. To avoid cracking, an extremely even deformation was necessary. Additionally, the material had to be softened by repeatedly heating it to a temperature of at least 750 °C.
Since gold alloy has a relatively low melting point of circa 960 °C, a very careful temperature control and an isothermal heating process were required, so as to avoid melting any of the surface. For this, the Bronze Age artisans used a charcoal fire or oven similar to those used for pottery. The temperature could only be controlled through the addition of oxygen, using a bellows.
Considering the tribologic conditions and the technical means available at the time, the production even of an undecorated Golden hat would represent an immense technical achievement.
In the course of its further manufacture, the Berlin Hat was embellished with rows of radial ornamental bands, chased into the metal. To make this possible, it were probably filled with a putty or pitch based on tree resin and wax - in the Schifferstadt specimen, traces of this survived. The thin gold leaf was structured by chasing: stamp-like tools or moulds depicting the individual symbols were repeatedly pressed into (or rolled along) the exterior of the gold. At least 17 separate tools (17 stamps and 3 cylindrical stamps) were used.
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