CONSERVATION OF A LYRE FROM UR: A TREATMENT REVIEW
5 CONSERVATION OF THE HEAD
The conservation treatment was divided into several stages. The horns and ears were removed from the head, and the separate pieces were faced. The section of beard that had become detached was dismantled first, followed by the section of beard still inside the head. The plaster was then removed from the head, horns, and ears.
5.1 EARS AND HORNS
The ears, being loose, were simply lifted off the wooden pegs. The adhesive holding the horns was removed with acetone, which was also used to separate the lapis horn tips from the plaster.
The ears, horns, and head (with the lapis hair tiles still attached) were faced with a layer of cellulose tissue and microcrystalline wax. Over this was put a layer of cheesecloth and wax, as it was not certain at that time to what extent the gold sheet would be able to hold its shape without a core. This heavy double facing later proved unnecessary, but it did enable the conservators to handle the head with confidence during the early stages of the treatment.
5.3 EXCAVATING THE BEARD
Starting with the section of the beard that had been detached from the head, the lapis tiles were faced with several layers of cellulose tissue and microcrystalline wax before work was begun on the back surface. The layers of silver and yellow paint proved resistant to solvents, but most of the paint was eventually removed with dimethylformamide and methylene chloride. Because of the poor condition of the silver, no attempt was made to remove every trace of paint. The silver sheet was very soft and friable, with a laminated structure and crumbling edges. As the silver was exposed, it was consolidated with polyvinyl acetate (PVA-AYAF) in toluene, and a temporary facing of tissue and microcrystalline wax was applied to the surface. Unfortunately, the PVA solution used as a consolidant for the silver did not set properly on some of the fragments, possibly owing to the presence of a previous consolidant. The PVA was removed with acetone, and after some experimentation, these fragments were successfully consolidated with Rhoplex AC-33 acrylic emulsion. (Paraloid B-72 [ethyl methacrylate copolymer, formerly Acryloid B-72], the first alternative tried, did not appear to be as successful as the emulsions, and the Rhoplex was superior to Jade 403.) A layer of fine muslin had been used as a separator between the silver sheet and the plaster that formed the primary support for the restored beard. Silver and muslin together were removed by inserting a spatula between the muslin and the plaster.
The work on the beard uncovered no conclusive evidence that the silver sheet had ever been treated. On the contrary, both the condition of the silver itself and the presence of fragments of copper alloy wires and pins (see sec. 2.2) strongly suggested that the backing was merely cleaned of superficial dirt before being incorporated into the restoration. The same was true of additional fragments of the silver sheet that had not been part of the restored head.
Attached to the interior face of the silver sheet were a number of small lumps of copper corrosion products. On the basis of appearance and experience (no analysis was done), these were described as predominantly carbonates, with some cuprite. Large areas of the silver sheet and the muslin were also stained green. After photography, a permanent support of fine fiberglass chopped-strand mat and Paraloid B-72 in toluene was put on the inner surface of the silver, and the temporary wax-and-tissue facing was removed from the outer surface. The support was put on the inner surface, covering details of interest, because it was assumed at the time that the fragments of the original silver sheet would be replaced on the newly restored beard.
After removal of the silver, work continued from the back of the beard. The plaster support below the muslin was composed of several thin layers (which showed distinct cleavage in many areas) and a thick layer reinforced with three modern wooden dowels (ca. 0.5 cm diameter, 6.5 cm long). The layers of plaster and wax were removed by softening the plaster with cotton packs soaked in hot water and then removing both plaster and wax with a scalpel. Beneath the plaster was the wax bed holding the lapis tiles. A sample of the wax was saved for future analysis, and the remainder was removed mechanically, with toluene as needed. The tiles were then placed on a tracing of the beard to preserve their original position and faced as a unit using tissue and microcrystalline wax.
Work was now started on the portion of the beard still attached to the head. Once the back surface was partially cleaned of paint, it was possible to see that the silver sheet extended into the plaster core of the head through an opening in the gold sheet. This open space, through which the beard had been inserted into the head during the first restoration, was too small to permit safe excavation of the plaster. This part of the beard was therefore dismantled from the front. Incorporated in the wax and plaster layers were three additional modern wood dowels that extended into the plaster core of the head. These were approximately the same size as the ones previously found in the lower part of the beard. It was now obvious that the beard had broken at the weak point between the two sets of dowels and that no fulllength reinforcement had been used in the restoration. By fortunate chance, the break fell between two sections of silver sheet, so that no original material was damaged.
Beneath the wax and plaster layers was the muslin separator, which peeled off when dampened with water, exposing a substantial area of silver sheet along with the remains of several corroded copper alloy pins or nails (see sec. 2.2). As the surface of the silver was cleaned, it was consolidated with Paraloid B-72 in toluene (which in this case was entirely successful) and then given a temporary facing of tissue and microcrystalline wax. The silver sheet, however, was still held firmly in place by the plaster inside the head.
5.4 EYE ASSEMBLY
Before removing the plaster from the head, the eyes (see. fig. 4a, page 247) were removed from the head by flowing toluene around the outer edges and removing the softened wax mechanically. The eyeball assembly was held together with what appeared to be paraffin wax, presumably left in place after the eyes were excavated. This wax was easily dissolved with ligroine (petroleum ether, boiling point 90–100°C), and the sections were separated and cleaned with the same solvent. The backs of the eyes were not protected when the head was restored, and plaster had flowed around the fragments of wire on the proper left eyeball, causing additional corrosion and making it very difficult to clean the fragile and completely mineralized wire.
The back of the proper right eyeball showed traces of copper corrosion embedded in a hard gray material that was insoluble in water, ethanol, acetone, toluene, and ligroine, as well as 50:50 acetone: ethanol. Additional traces of this gray substance were found between the elements of the eyeball assembly, together with paraffin wax. This substance is almost certainly a modern restoration material. It was never identified, but a sample was kept.
All the shell and lapis elements were cleaned in ligroine, leaving the gray material in place. Both eyeballs were reassembled using Jade 403 PVA emulsion adhesive. The plug of gray material was replaced in the back of the right eyeball, but the coiled wire from the left eye was kept separate for later examination. The details of the eyeball construction (like those of the horn tips) had not previously been recorded.
5.5 REMOVAL OF OLD PLASTER CORES
The horns and ears were soaked in warm water for several hours, and the softened plaster was removed mechanically. Metal tools were used initially, but once the plaster had been excavated to 5 mm of the interior surface, only wooden tools were employed. The gold sheet had not been lined, and in several places the plaster adhered tenaciously to the metal, but it was eventually detached after longer periods of soaking. The tiny gold tacks in the proper right ear were now visible: all four were intact and 5–6 mm long (see fig. 2b, page 246).
The plaster inside the head was first softened with packs of cotton wool soaked in hot water. The exposed silver sheet was protected with polyethylene sheet. As the cavity grew, small amounts of water were poured in and left for several hours at a time. When the excavation had progressed to within 1 cm of the interior surface, the remaining portions of the silver sheet could be removed. With the silver out, the head could safely be immersed in water, and after an overnight soaking the rest of the plaster was removed without difficulty.
Unfortunately, no separator had been applied to the outer surface of the silver sheet before the beard was inserted into the head. The plaster thus flowed into every crack and crevice in the silver and could not be completely removed.
Three separate batches of plaster had been used to fill the head. An initial batch of hard white plaster was poured into the nose. The restored beard was then inserted through the opening in the gold sheet and held in position with wax. A second pouring of similar plaster secured the beard in place and filled most of the head. A third batch of softer pale pink plaster filled the rest of the head cavity and held the iron armature in position.
It was impossible to tell whether the head had been entirely filled with white plaster and then excavated for the armature or whether the space for the armature was left from the start. In any case, the difference in materials would support the theory that the construction of the soundbox and the attachment of the head to the soundbox were done by a different person, and/or at a different time, than the restoration of the head itself.
With the interior surface of the gold head exposed, two sets of small holes could be seen on the edge of the gold sheet under the horns, matching the pairs of holes on the neck strip. There were no original tacks present, and the two sets of holes were not properly aligned. It was also then evident that the gold sheet extended only a few millimeters under the bottom row of lapis hair tiles, which were embedded in the same type of wax as the beard tiles. When this wax was removed, the backs of the hair tiles proved to be plain, unlike those of the beard, and so must have been held in position on the core entirely with bitumen adhesive.