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Conserving the Mihrab (prayer niche)

Mihrab (prayer niche) 
Iran, eighteenth century with later repairs
Stonepaste; glazed (mosaic technique) 
Overall: 96 1/4 x 69 1/4 x 19 3/8 in. (244.5 x 175.9 x 49.2cm) 
Doris Duke Foundation for Islamic Art, 48.422
On view near the central courtyard

Conservator Laura Gorman taking a sample of the mihrab during round-one testing, October 2004. Doris Duke Foundation for Islamic Art, Honolulu, Hawai'i.

This ceramic tile mosaic mihrab, which Doris Duke (1912–93) purchased in 1975, was originally attributed to the “15th or 16th century.” During a 1994 appraisal however, it was dated much later: “probably 19th or 20th century.” The uncertainty in the date of manufacture was shared with several American and European museums, who had also questioned the date of similar tile panels. In the field of Islamic art history, marketing strategies and restoration efforts make it especially difficult to assign dates of manufacture to ceramics. On the art market, “old” age typically equates with greater value. As a result, ceramics are often marketed as centuries older than they really are. In addition, because ceramics are extremely fragile and susceptible to breakage, many ceramics on the market are often made up of fragments of old (“original”) and newly manufactured parts, assemblages known as “pastiches”. For example, during conservation treatment, a mina’i (Persian: enamel) bowl in the DDFIA collection was discovered to be composed of original material in its interior, while the majority of its outer rim was restored from fragments of another vessel.

In the fall of 2004, the DDFIA submitted samples from the mihrab for thermoluminescence testing (TL), a scientific process used to date minerals, such as clay, that have been subjected to intense heat. (For further information on TL visit Oxford Authentication Ltd.)  

The sampling process 
A joint curatorial–conservation team extracted four samples, packaged them carefully, and sent them to a professional lab in Germany for TL testing. Clay was exposed in a number of places on the panel, making it possible to take several samples from different locations. This is preferable given that samples can easily be contaminated, particularly by light and unfired materials such as plaster and dirt. In addition, a single ceramic object, such as themina’i bowl mentioned above, can include a variety of old and new parts. Thus, the results of one sample might not accurately reflect an object as a whole.

Of the four submitted samples, two were rejected as contaminated. Samples 1 and 2, respectively taken from the left and right border inscriptions, yielded two different results. One yielded a date of 1856; the other a date of 1758.

Interpreting the results 
The results of the TL testing were not necessarily surprising, but prompted unanticipated questions such as, “what could explain over a century of difference in the dates of the border?” and, “If the border had such a range of dates, might the rest of the panel yield even more dates?” It became apparent that the complicated history of the mihrab could not be fully or accurately explained by just two successful samples and that a second round of TL testing was needed. Ideally, the results would confirm, or least clarify, the evidence collected in round one.

Detail of the mihrab showing the area where a sample was taken for round-two testing, December 2004. Doris Duke Foundation for Islamic Art, Honolulu, Hawai'i.

Round-two sampling and results 
During the second round of testing, five additional samples were taken. Two samples were contaminated and discarded, but three yielded dates of 1920, 1920 (again) and 1870.

After two rounds of testing, five successful samples yielded single dates ranging from 1758 to 1920. How was this assorted data to be interpreted? The answer to this question remains elusive, but at least two explanations are plausible. The panel could have been made in the eighteenth century and restored at least twice, in both the nineteenth and twentieth centuries. A second explanation was suggested by the scientist in charge of round-two testing as it was speculated that the object may be composed of parts from different origin. Perhaps the mihrab was made by a twentieth-century artist who used both contemporary ceramic body and similar looking fragments salvaged from broken eighteenth- and nineteenth-century tile panels. The phenomenon of integrating old fragments into new compositions is popular in many Islamic arts media, particularly textiles, and should not be dismissed when considering ceramic.

Although the TL project left some unanswered questions, it also stimulated new and exciting avenues of scholarly inquiry.  

Project led and reported by Keelan Loftin, Assistant Curator. 
Samples taken by Laura Gorman, Objects Conservator.

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