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Making the Invisible Visible: Conservation and Islamic Art

April 2–August 4, 2013

Examination and Conservation of Mina'i Ceramics

Jean-Francois de Laperouse
Conservator
The Sherman Fairchild Center for Objects Conservation


Bowl. Seljuq period (1040–1196), 12th–13th century. Attributed to Rayy, Iran. Stonepaste; polychrome in-glaze and overglaze painted and gilded on an opaque white glaze (mina'i). H. 3 1/2 in. (8.9 cm), Diam. 8 1/4 in. (21 cm). The Metropolitan Museum of Art, New York, Rogers Fund, 1913 (13.93.1). See a slideshow of mina'i vessels that are on view or in storage.

At the start of the reinstallation project, conservators surveyed the entire collection with curators to establish examination and treatment priorities. The condition of the ceramics, including the mina'i ware, was of particular concern as it was known that many had been restored in the past but it was not clear how much of their original fabric survived under discolored restoration paint. Produced in the Kashan region of Iran in the late twelfth–early thirteenth century, mina'i vessels were covered with an opaque lead-tin oxide glaze—either white or tinted light blue with copper salts—that was meant to imitate Chinese porcelain. Their surface decoration was executed using both inglaze colors—pigments that suffused into the upper surface glaze in a first firing—and overglaze enamels consisting of pigments mixed with glass frit that melted and fused to the glaze in a second firing. Unfortunately, the ceramic body used—a mixture of crushed quartz, glass frit and white clay—was not as durable as porcelain, and almost all examples of mina'i ware have been incompletely retrieved in fragmentary form. Previous restorers filled losses with plaster, fragments from other old vessels or newly fired ceramic shards which they then disguised with paint.

Ultraviolet (UV) light can be an extremely useful tool in identifying modern restoration paint on ceramics. The binders in the paint—the drying oils or organic resins that keep the pigment particles together and affix them onto a surface—will absorb UV light and reflect a visible fluorescence that will contrast with the unpainted areas. Since paint was often applied over original surfaces to hide break lines and blend large restorations into surrounding areas, the UV reflectance images by themselves did not provide a complete picture of an object's condition. Comparing UV reflectance images with radiographs taken of each vessel, however, allowed us to determine accurately the exact extent of losses. (Records were kept of all radiographic exposures to ensure that any possible effect on future thermoluminescence dating could be accounted for in the future.) Using the information obtained, photographs could be edited digitally to illustrate various treatment scenarios before treating the objects themselves.

Through discussions with the Islamic curators, it became clear that our primary concern was to reveal original surfaces as much as possible and to remove extraneous shards. In some cases, old restorations were preserved if they were not misleading and were confined to areas of loss, as some of these restorations were almost one hundred years old and had acquired their own historic value. When the repainting of losses was required, the restoration of original motifs such as repeated designs or framing was done occasionally so that losses would not be too visually obtrusive.

See a slideshow of mina'i vessels that are on view or in storage.


Additional Reading

de Lapérouse, J-F, K. Stamm and V. Parry, "Re-examination and Treatment of Mina'i Ceramics at The Metropolitan Museum of Art," in Pilosi, Lisa, ed., Glass and Ceramics Conservation 2007: Preprints of the Interim Meeting of the ICOM-CC Working Group, August 27–30, 2007, Nova Gorica, Slovenia (Nova Gorica, Goriski Muzej Kromberk, 2007), pp. 112–119.

Koss, K., B. McCarthy, E. S. Chase and D. Smith, "Analysis of Persian Painted Minai Ware." In Scientific Research on historic Asian Ceramics: Proceedings of the fourth Forbes Symposium at the Freer Gallery of Art, Archetype Publications Ltd (2009), pp. 33–47.

Pease, M., "Two Bowls in One." The Metropolitan Museum of Art Bulletin, New Series, Vol. 16, No. 8 (April 1958), pp. 236–240.