In 1998, the Islamic Art Department acquired a wooden writing cabinet—qalamdan in Persian—produced in India during the mid-seventeenth century (Figure 1), when Muslim rule within the country was divided between the Mughal Empire in the north and smaller kingdoms of the Deccan in the south. Complete with drawers and compartments, this box served as a portable desk, and the importance placed on the art of writing in Islamic cultures is expressed in the precision of its wood joinery and the sumptuous decoration on the exterior. The top and sides are covered with wide bands of gilded metal sheet separated by stepped ridges into rectangular and square fields. Silver floral ornament, executed in ajouré and set against a dark red textile background, is contained in cartouches, rosettes, or lobed medallions cut into each field (Figure 2).

Assuring the preservation of objects of mixed materials presents unique challenges. Forms of deterioration characteristic of different media vary according to their nature, and in addition to exposure to deleterious environmental conditions damage may result from contact between incompatible materials, or from past treatments designed for one material that compromised the stability of another. Changes in appearance resulting from surface deterioration often obscure the interplay between materials and finishes that are essential for a full appreciation of a work of art. Only fragments of the textile survive on the writing cabinet, and because its original appearance has also been significantly altered by silver tarnish and an accumulation of dirt and polishing residue, treatment was required before the box could be placed on display (Figure 3).

The repeating floral motifs on the exterior were produced by stamping silver sheet into intaglio metal dies. Such dies, known in India as thasa, thappa, or chhancha, have been used extensively in the manufacture of Indian jewelry. Radiographs reveal thin borders, now masked from view, around these delicate openwork decorations, which helped to prevent deformation during working and handling (Figure 4). Thicker silver sheet was used on the moldings of the lid and bottom, and gilded metal braces reinforce the edges on the sides of the box.

Qualitative X-ray fluorescence analysis of the strap hinges and the interior drawer pulls indicated that they are fashioned from a brass alloy, while the substrates of the gilded panels and exterior handles are unalloyed copper. The gold was applied using an amalgam technique. Facilitated by the presence of mercury, the gold is bonded to the substrate through the interdiffusion of gold and substrate atoms during heating. Where not accessible to burnishing tools and protected from wear, the gold layer still displays the porous texture typically produced by the mercury as it volatilizes.

Other materials used in the fabrication of this box derive from living sources. The wood may have come from the sisham tree, an indigenous hardwood related to rosewood that was commonly used in the construction of Indian writing cabinets of similar date. Microscopic examination of fibers from the plain-woven textile on the exterior revealed it to be wool rather than silk, as had been assumed when the box was acquired. Mughal rulers, beginning with Akbar (r. 1556–1605) and continuing with Shah Jahan (r. 1628–1658), made a point of patronizing wool production, and the use of this textile may have implications for establishing the cabinet's provenience within India. Viewed under ultraviolet light, the textile fragments exhibit an orange fluorescence, most likely indicative of madder lake, a dye derived from indigenous chay roots or other plants of the Rubiaceae family.

The combination of metallic and organic materials is cause for concern with regard to the box's long-term stability. Keratin, the structural protein of wool, contains sulfur, which can promote the corrosion of metals, and the volatile organic acids found in many wood species induce corrosion as well. This problem may be less of a concern with aged wood, but on the other hand, the interior surfaces of this box have been treated with a dressing that contains beeswax and it is probable that the free acid content of this material contributed to the corrosion of the interior brass fittings. In spite of the potential for further deterioration, the dressing was not removed, as it may have been applied when the box was originally manufactured. The fact that works of art can suffer from vapors emitted by adjacent materials has motivated extensive efforts by museums to use safe products in the construction of display cases (see The Oddy Test improved).

Cleaning techniques used for works of mixed materials must be highly selective, and dry cleaning methods are usually preferred because the flow of liquids can be difficult to control. For removing superficial tarnish from silver inlays on damascene metalwork without polishing the silver or disturbing adjacent metal surfaces, non-abrasive vinyl erasers have been found effective. When the build-up of tarnish is more severe, an aqueous paste of .05 micron alumina can be used for mechanical spot cleaning.

In this case, however, preliminary cleaning tests indicated that pretreatment with a thiourea solution was required to soften the thick sulfide layer on the silver fittings so that it could be removed mechanically without damaging the metal surface. Since embrittlement of the various metals and the complexity of the assembly preclude removal of individual elements for cleaning, the thiourea was applied to the silver in situ with microswabs in order to confine it as much as possible to the silver surfaces. Any thiourea absorbed by the porous textile and wood was extracted using a poultice of synthetic colloidal clay and distilled water. This poultice also proved effective in softening accretions on the surfaces of the wood, textile, and gilded elements. To minimize wetting of the hygroscopic materials, as little water as possible was used during removal of the poultice. Since they do not detract from the overall appearance of the writing box, old repairs were left intact and losses not restored, and after treatment the qalamdan communicates once more some of its original brilliance while preserving evidence of its age and history.

A nitrocellulose lacquer was applied to the silver fittings in order to prevent retarnishing. This decision was made reluctantly, as lacquers slightly alter the appearance of silver and eventually degrade, requiring removal and reapplication. Exhibition cases can be equipped with filtration systems to remove the ambient sulfur that causes silver to tarnish, but the effectiveness of such a system when the silver is directly adjacent to or actually touching the source of the corrosive agent has not been established. Furthermore, it is anticipated that this work will be loaned to other institutions, and given the difficulty of continuously controlling the box's environment during transport, storage, and display, the lacquer ensures that it will not be subjected to lengthy or repeated tarnish removal treatments in the future.

Even though the silver elements have been lacquered, the quality of the environment in which this box is displayed or stored still is critical. When two metals are in contact, exposure to high relative humidity, salts, or acidic compounds can lead to accelerated corrosion of the less noble metal. On gilded copper alloys, corrosion of the substrate often causes lifting and loss of the gold, as well as darkening of the surface due to the migration of copper oxides. As the substrate cannot be isolated or treated, its stabilization is dependent on environmental control. While dry environments tend to inhibit the formation of corrosion, low humidity levels are not suitable for organic materials, and the competing needs of all materials present must be taken into consideration to establish an appropriate median.

Jean-François de Lapérouse joined the staff of the Sherman Fairchild Center in 1990, shortly after receiving a Certificate of Conservation from the Institute of Fine Arts, New York University. Primarily involved in the study and treatment of objects from the Islamic Art and ancient Near Eastern Art Departments, he recently completed the coursework requirements for a doctorate in ancient Near Eastern art at the Institute with assistance from the Museum's IFA/NYU Scholarship for Course Tuition program.

Fiber identification was carried out by Maya Naunton, Polaire Weissman Fellow, The Costume Institute.