Old Repairs on an Islamic Bowl

Last week, I started to work on an Islamic bowl. The bowl had been bought rather than excavated, so little is known about its origins. Worse, the records for the bowl are incomplete. Although we have some slides showing the bowl in pieces and chunks, we do not have an information about the previous treatments and repairs. From what we can tell between the incomplete record card and slides, the acquisition of the bowl was in 1997. It probably came with some old repairs or inpainting, as it was not in individual potsherds in the slides. In 2000, a conservator at the Kelsey pieced together the rest of the potsherds. The treatment was incredibly invasive. Water soluble plaster was used as a gap fill and to cement slivers of loose glaze. The gap fills were painted to blend in with the rest of the decoration. Though the Islamic bowl looks good to those who do not know, its actually quite bad conservation. The pieces are put together poorly, and the glaze is deteriorating. The bowl probably was whole in 2000, but has since broken. It is now in eleven groups and a bag of flakes and slivers.

Based on the iconography and colors of the bowl, I would identify this as mina'i ware in the Kashan style from the Seljuk period. That would place the origin of this piece in 13th century Iran. Blue and turquoise were often used in this period, the latter thought to be good luck, and a white or beige ground is typical. Moreover, the large, haloed head and seated or standing figures in patterned clothes without a clear setting is often seen on Kashan wares. The pigeon-like birds, floral swirls, and Quranic inscriptions are also characteristic.

 Seljuk Horsemen, Mina'i pottery bowl, Kashan, c. 1200

To better view the old repairs, I looked at the bowl under ultraviolet light. The synthetic material often used in old ceramic repairs fluoresces in UV light. Although not all the material is visible this way, many of the repaired sections glowed yellow and white. It is possible that cellulose nitrate was used, which typically fluoresces pale yellow and is soluble in acetone, but we still cannot tell what it is.

I had to take apart all the old repairs and clean off the old material so that I can conserve the potsherds. I tested the adhesive, plaster, and paint for solubility. Using cotton swabs on small pieces, I tested warm water, acetone, ethanol, and a solution of half ethanol and half acetone. The effects were minimal. The plaster was soluble in water and the adhesive was soluble in warm water and 1:1 acetone/ethanol, but nothing was very effective on the paint. On one rim section, I dripped 1:1 acetone/ethanol along the joins using a pipet and was able to break apart the pieces. I placed another section of the rim into a bath of warm water which softened the adhesive and allowed the pieces to fall off. The two techniques took approximately the same time, but the water bath also started to dissolve the plaster gap fills. For the rest of the pieces, I placed them in warm water. The bowl then fell apart in the water as the adhesive and plaster dissolved. In the end, I had over 150 pieces, a large number of which are probably entirely plaster gap fills. The next step is to determine which are original and which are remaining plaster pieces.

One rim section alone consisted of 36 pieces, 12 of which turned out to be plaster gap fills. Plaster was also found between the front and back glaze, and supporting damaged pieces. Some of the glaze was also painted over. Much of the center section is plaster and paint, so it will be hard to put back together. This will be a difficult repair. The end product will probably look quite different, and the old repairs might be more pleasing to the eye, but it will be more stable and better in the long run.