European Bronze Age Gold in the British Museum

Alessia Murgia, Martina Melkonian and Benjamin W. Roberts

Technical analyses on selected objects by Susan La Niece

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Gold Sources and Technology

 

Gold is found throughout Europe in both primary sources, where it is found as veins running through the rock, and secondary sources, where it has been separated from the rock, usually due to processes of erosion (Morteani and Northover 1995; Borg 2010).

Secondary gold is encountered as alluvial or placer gold sources (gold-bearing sediments sorted by river action). Primary gold is extractable by the simple procedure of local quarrying, heating and quenching the coarse rock, crushing it and panning the resultant sand, whilst a panning technique could be used for secondary gold sources and alluvial/placer sources. As there are currently no known gold mines in Europe dated to the Bronze Age, it is assumed that gold was obtained using archaeologically invisible methods such as the panning technique. There have been substantial research projects aiming to provenance gold objects back to their gold origins through compositional or isotopic measurements (e.g. Hartmann 1970; 1979; 1982; Northover 1995; Chapman et al. 2006; Warner et al. 2009; Borg 2010; Standish et al. 2013). The complexity of the geology, the relatively small number of gold sources sampled and the Bronze Age metallurgical production processes, such as re-melting, recycling and alloying, make it very difficult to achieve a clear match. There is no evidence of the purification of the native gold; however the presence of higher levels of copper and tin in objects dating to the later phases of the Bronze Age potentially indicates the manipulation of the gold composition (Taylor 1980, 13–21). The techniques employed on gold by Bronze Age craftspeople must therefore be identified through the close examination and laboratory analysis of the objects and by supporting experimental replication as demonstrated by the Brack’s Farm torc study (Taylor 1980, 8–13). Unfortunately, relatively few objects in the British Museum collection have been scientifically analysed or replicated leaving many Bronze Age goldworking technologies unexplored and relying upon the analysis of morphologically similar objects. The knowledge of both archaeology and goldsmithing achieved by Barbara Armbruster has proved invaluable in furthering understanding (e.g. Armbruster 1995b; 2000; 2010b; 2011).

Gold Distribution Map

Primary and secondary gold sources in Europe (redrawn by Craig Williams from Borg 2010, 738, Abb 2).

Whilst the techniques used in manipulating gold in Iberia have been subject to extensive analysis (Armbruster 2000), recent research in the United Kingdom and Ireland has tended to concentrate on specific techniques such as sheet-working (Needham 2000) and wire-working (Cahill 2009) or on specific object types such as penannular rings (Northover 2000; Meeks et al. 2008) and lock-rings (La Niece and Cartwright 2009). A Bronze Age gold workshop has yet to be discovered in the United Kingdom or Ireland, although stone and bronze tools have been identified for casting and deforming gold (Armbruster 2010a) such as the Middle–Late Bronze Age small copper alloy anvils (Ehrenberg 1981) from Knowle Hill, Staffordshire, England, and Bishopsland, Co. Kildare, Ireland (Eogan 1983a, 36, 226).

The main goldworking techniques identified in the Bronze Age gold objects from Britain and Ireland in the British Museum collection are outlined below.

Casting

The casting technique involves the melting or re-melting of gold nuggets or objects in a clay crucible. The liquid metal is then poured into a stone, clay or sand mould so that the metal forms a specific shape upon cooling. Casting can occur in open and bivalve moulds as well as in more complex moulds using the lost-wax process. The lost-wax casting technique involves the initial creation of a desired form in wax. The wax form is then coated in a clay mould and the liquid metal is poured into the mould. The wax melts and flows out of the mould and is replaced by the metal. Upon cooling, the metal is the shape of the original wax form.

Chasing, embossing, repoussé and pointillé

The embossing or repoussé technique involves using a rounded tool, probably of wood, copper or bronze, to push a small section of the sheet metal surface up from the back to create a raised surface. When pressure is applied from the front to create a lowered surface, it is termed chasing. When it is used to create a series of small dots, it is known as pointillé.

Fusing

Fusing is the joining of one or more gold pieces by heating and placing together the opposing edges which are then allowed to cool.

Gold plating

The gold plating technique involves the placing of gold sheet or foil over a solid body to create the appearance of a new surface with a different colour to that of the inner core. In penannular rings, gold plating is used to cover copper alloy and tin cores. This technique is also termed gold foil covering and there is disagreement whether the term plating should be used as gold plating is technically a chemical or electrochemical process.

Hammering, beating and sheet-working

The hammering or beating technique involves the repeated striking of gold on a flat surface in order to manipulate the shape. It is employed primarily to create gold sheet and in riveting. The sheet-working technique consists of the hammering of a gold ingot into a thin sheet or foil. It is thought that after this first phase of hammering, Bronze Age smiths would have hammered the sheet over a soft material, such as wood, resin or leather, to prevent the possibility of breaking it and to relieve the hammer marks. The sheet would then have been cut to shape and decorated. The main decoration techniques used on sheet objects were incising, embossing/repoussé, pontillé, punching and perforation.

Incising

The incised technique involves the use of a pointed tool, probably a flint, copper or bronze awl (thin pointed tool), to create lines in the surface of the gold sheet in patterns ranging from linear to geometric.

Inlaying

The inlaying technique involves the winding of continuous wire strip along a solid body. A contrast can be created if the gold colour of the body and the strip are different, giving the appearance of alternating stripes in penannular rings.

Perforating

The perforating technique involves a sharp tool, probably a flint, copper or bronze awl, to create a small hole in the sheet metal surface.

Punching

The punching technique involves a pointed tool, probably a stone, copper or bronze punch, to push a small section of the sheet metal surface down from the front to create a depressed motif.

Riveting

The riveting technique involves the insertion and hammering of a gold pin with an expanded head, termed a rivet, through aligned holes. The pointed end is then hammered flat as well so that two or more separate pieces of gold are joined.

Soldering

The soldering technique involves the joining of one or more gold pieces by melting a filler metal into the joint. The solder melts at a lower temperature than the pieces to be joined.

Stamping

The stamping technique involves applying pressure using a specifically shaped tool in order to create a distinct impression on the surface of the metal.

Twisting

The twisting technique involves the complete rotation of an object, usually a gold bar, ribbon or wire, on its vertical axis. A further variation on the twisting technique involves making three or four cuts into the section of the gold bar, hammering up the angles into flanges and then twisting it along its length. This is termed flange twisting.