EXARC Journal (Jun 2017)
The Colour Palette of Antique Bronzes: An Experimental Archaeology Project
Abstract
Bronze is an alloy of copper and tin, with lead also added. Hellenistic and Roman bronze objects have a variable percentage of metals, and because of this the colour of the alloy will differ depending on the proportions. The colour of the alloy can be maintained by polishing, but it is also possible to give a patina to the surface of bronze using a reagent. Other metals and alloys (copper, silver, gold, Corinthian bronze) can be inlaid by damascening, or by plating to create polychrome decorations. Unfortunately, copper alloy materials recovered from archaeological sites suffer from the effects of time and deposition, which may lead to corrosion and discolouring of the surface, often appearing green or brown. Archaeological bronzes also may suffer from overly aggressive restorations which scour original surfaces or cover them with a layer of paint imitating green corrosion. The collection of swatches I created gathers the spectrum of colours of antique bronzes, and allows for a restoration the original colours of the objects of my study: Greco-Roman bronze furniture. This study combines the processes of the lost wax method and the addition of polychrome bronze surfaces (patina, inlay and gilding). Some platelet samples from this collection of swatches have also been analysed to determine their elemental composition and their patina, so as to compare them to archaeological materials. Initial results suggest that the colours of bronze luxury furniture vary greatly, and that the spectrum of colours is a product of bronze alloy composition, and of the techniques used in finishing the surface, either polishing or patina application.
