The decorative techniques of the Celtic smiths can be divided in to the mechanical manipulation of the metal itself, from engraving to casting, the mechanical addition of other materials such as enamel/glass inlays or bronze claddings, and the use of metallurgical or chemical techniques for plating, etching and patination. The first two of these are well-known elements of Celtic art but the third has seen much less study and, because of the limited space available, will be the topic dealt with at greatest length here.
The mechanical decoration of bronze can be split between three categories, the first Involves the removal of metal, for example In engraving (Lowery et al. 1976). The classic example of this in Britain Is the decoration of the mirror plates of the Late Iron Age, where engraving techniques were used to produce the linear outlines of the design and to fill in parts of it with textured surfaces such as basketwork. Another application was in shield plates; in the Tal-y-llyn hoard already referred to this is combined with the shaping of sheet bronze and brass in repousse. Repousse and chasing imply that metal is moved rather than removed. Some of the best known examples are in the shields (Stead 1985) but might also be seen, for example, in scabbards such as that from Little Wittenham, Oxfordshire. The main panel of the front plate has been textured with a ladder-like pattern of narrow, closely packed repousse rungs (Raftery 1991) while the upper and lower ends have a panel of typical curvilinear Celtic decoration, also in repousse, with added ornament in the form of studs and appliques. The same styles of decoration might also be created by casting them directly. This is particularly associated with Snettisham gold art but was also repeated in bronze. Inserted into both sheet and cast bronze might be inlays of other materials. This might be anything from coral to tin to glass. The use of coloured opaque glasses is especially favoured in later iron age art in Britain, with some spectacular effects (Haseloff 1991; Brun and Pernot 1992). The use of bronze as a cladding has already been described, but bronze or brass might also be used as a fretwork against a contrasting backing, which might be tinned copper in the Tal-y-llyn hoard or, perhaps, patinated bronze in the Lochar Moss collar (MacGregor 1976).
Plating techniques could also be used to effect, either covering an object completely or just forming part of the design. Study of the corroded remains of a sword scabbard from a warrior grave at Kelvedon, Essex, England, datable to c. io BC, showed that an otherwise plain faceplate was decorated with a longitudinal strip of tin plating thick enough to stand proud of the surface. When newly made and polished, the tinning would show as a silver strip against the golden background of a medium tin bronze; the strip itself has accurately straight and parallel edges. It was created by masking the outer parts of the faceplate with clay, heating the bronze sheet, fluxing the exposed strip with resin, and then rubbing the hot bronze with a stick of tin. Above the melting point of tin (232°C) reaction between the bronze and tin is instant, a series of compounds of copper and tin being produced, with excess tin remaining on the outside. The plate was then heated to a higher temperature approaching 6oo°C; the bronze-tin reactions continued, although in this case they did not go to completion. Some unreacted tin remained on the surface but this is now corroded away, exposing the underlying compound layers (Northover and Salter 1990; Jones 1992).
This is one example of the way in which Celtic craftsmen used metallurgical and chemical techniques to decorate, conceal, texture or patinate bronze surfaces. The decorative use of tin plating goes back to the Early Bronze Age (Meeks 1986) but its appearance is intermittent. Within the period we are reviewing here one of its earliest uses is on some brooches of the sixth-fifth centuries BC; excellent examples come from the Diirrnberg in Austria (Moosleitner 1991). It then disappears from the Celtic west for a long period but the technique was not forgotten elsewhere. It can be seen on south Italian bronze armour of the fifth century, for example (Born et al. 1990). As far as is known at present, tinning in the form of plating reappeared in Britain in the second half of the first century BC but tin had been used for inlays early in the La Tene period. A La Tene I brooch from Flag Fen (Jones 1992) has its bow
Deeply hollowed and filled with tin metal, while an iron pin from Llwyn Bryn-dinas, Powys, Wales, has a tin bead cast onto its head (Musson et al. 1993). The sword scabbard just described is one of the earliest surviving examples of true tin-plating after its reintroduction but the technique became very popular in the years around the Roman conquest, with tinned brooches, vessels and decorative elements such as the Tal-y-llyn plaques already mentioned.
Bronze itself was used as a plating, now on iron. If iron is hot-dipped into molten bronze there is a fast reaction and a strong and coherent plating is formed. This method was used particularly to plate iron horse-harness but the motivation is not clear (Northover and Salter 1990). It may have been done simply for the sake of appearance but equally it could have been used to improve the wear resistance of the iron. There are several good examples in the Llyn Cerrig Bach, Anglesey, votive deposit (Savory 1976; Lynch 1991). For the use of precious metals in plating on copper and bronze see the section on gold.
World History
