Objects in focus
Conservation and Observation: more on a copper alloy cauldron from Ur

This post continues the investigation of a copper-alloy cauldron, excavated at Ur (located in present-day Iraq) in the 1920s or 1930s by the archaeologist C. Leonard Woolley. Those of you who read the previous blog post on the cauldron will remember that the cauldron, initially a sorry sight, yielded a surprising amount of information, even allowing a speculative suggestion about its provenance.

The blog concluded with the suggestion that more information could be gained through further study, X-radiography and analysis.

Balancing the need for a comprehensive investigation against the fact that there were many objects requiring assessment and treatment for the project, led to a decision to adopt a minimal approach to the conservation of the cauldron. In its current storage (in controlled environmental conditions) and supportive packing, the object is stable and the likelihood of further deterioration is reduced. In addition, much information may be gleaned from a non-interventive approach to treatment.

As mentioned in the previous post, the cauldron is lined with a layer of waxed calico on the interior (over a layer of soil) and partially lined on the exterior. The waxy lining is one of the few remaining examples of an excavation practice frequently used by Woolley and is therefore a physical document of this process – part of the object’s history. This material and the concreted soil have probably prevented the complete collapse of the cauldron. However, this also means that the cauldron interior and underside are obscured.

Conservator working on the large copper alloy cauldron.

One of the most widely used non-interventive investigative tools in conservation is X-radiography. This produces a visual record of the form and structure of objects, when soil and corrosion products (and waxed calico!) obscure surfaces. X-radiography may also provide valuable evidence of metal-working processes, and of decorative features.

Detail of handle fittings.

Before studying the cauldron bowl, the detached cauldron handles were X-radiographed and a number of interesting features were revealed. In an X-ray, a lighter tone indicates the presence of denser metal.  This may be seen in the handles of the cauldron and is particularly noticeable in the three rivets on each handle fixing. The halo of a similar light tone that surrounds each rivet first suggested a form of spacer or washer. However, this is most likely to be the splayed outer or inner faces of the rivets, hammered flat.

X-radiograph of the cauldron handles and section of rim.

On the right handle fixing, on the upper right, what appears to be a stress fracture from original working is visible.  When cold-working metal, the material has to be repeatedly annealed (heated and cooled) to keep it malleable, otherwise it becomes brittle and fractures, as has happened here.

As the X-radiograph above demonstrates, the rim section, although more deteriorated than the handles, can be seen to have horizontal striations, that is, a banded or striped effect. It is likely that this demonstrates different densities of metal and therefore could indicate the way in which the metal was extended and formed through continuous sequential rows of hammering. Much of the shoulder of the vessel is missing, so it is not known whether the rim and body of the vessel were formed of separate pieces of metal, as there are no traces of rivets or seams. However, vessels of this type were usually formed from a single sheet.

Some features of the handles were identifiable without X-radiography. It was obvious, for example, from their physical appearance that a considerable amount of solid metal survived in them.  Cleaning the rivets of the handle; the physical removal of corrosion from their surface, would also have allowed the form of the rivets to be identified, had this particular investigative approach been taken.

Most exciting, however, were the results of the X-radiographs of the cauldron bowl. These revealed that the cauldron had what must have been an almost perfectly circular base attached to its underside.  Part of this is very corroded and fragmented, but much survives intact. The precision of the curve of the circle is impressive and the crisp line suggests that it may have been cut with knife or shears.  The large, precisely spaced square rivets are very similar in appearance to those of the handles. The base also appeared to be raised (hammered to shape over an anvil or former) to form a shallow foot.

Left: X-radiograph of a section of the cauldron bowl. The X-radiography plate was not large enough to include the entire cauldron. Right: X-radiograph of cauldron bowl (detail).

As mentioned above, copper alloy vessels such as this were usually beaten from a single sheet, and an attached base would have provided additional strength.  In Woolley’s metal vessel typology, the Type 49 cauldron, of which this is an example (as identified in my previous blog post), does not include a riveted base. The closest parallel is Type 9, a round-bottomed vessel, but in this case the base is not riveted but soldered to the underside of the vessel.

Type 49 and Type 9 cauldron profiles. C.L Woolley, Ur Excavations: II, The Royal Cemetery (1934), p.302.

Although just another small step in understanding the cauldron, these revelations about the structure have not previously been recorded and have been hidden for the best part of a century, if not for millennia.

Investigation of the traces of mineral-preserved matting and analysis of the crust of sooty deposit around the rim of the cauldron was not possible in this phase of investigation, but hopefully this will be something that will be taken up by conservation and science colleagues in future.

Body 33, Great Death Pit (PG 1237).

X-radiography was used on a number of Ur objects in order to identify features of interest that might be obscured, and on occasion, as with the cauldron, this proved valuable.  One of the more poignant of these examples was another object with its waxed calico support preserved.  This object, unlike the cauldron, has a known provenance within the mid-third millennium BC Royal Tombs from a large grave (PG 1237), named by Woolley as the Great Death Pit. The object is part of a headdress belonging to Body 33, one of the 68 female burials there. Little is visible amidst the obscuring dirt and wax although one or two beads have been cleaned in the past.  The X-radiograph however, reveals the crushed remains of a three-flowered comb, a common element of the elaborate headdresses found in this burial group. The outline of the comb also features on the schematic drawing of Body 33. Woolley aimed to preserve the integrity of the Ur finds when lifting them and this is a good example of this process.  Its poignancy lies in the fact that it is fixed as it was at the point of excavation, retaining a sense of association with its third millennium BC origins.

Left: The X-radiograph of the headdress reveals the crushed remains of a three-flowered comb. Right: Little is visible amidst the obscuring dirt and wax although one or two beads have been cleaned in the past.

A number of objects of this type are held in the British Museum: one, a complete headdress along with the remains of the wearer, is on display in Room 56.

Headdress from 2600 BC, Ur. On display in Room 56.

The current phase of the Ur Digitisation Project (now Ur Online) concluded on 30 June 2016.