Islamic bowl reconstruction

The Islamic bowl was difficult to reconstruct. It had many issues with it: large gaps, worn or broken edges, and laminated pieces. 

Top: Front of bowl, with gray areas indicating plaster; Bottom left: Back of bowl, with grey areas indicating plaster; Bottom right: pieces after disassembly.

I started with the easy part, the rim, and worked my way inward. The rim was mainly intact, but even so, there were weak joins and unstable sections. I glued each section together, placing the sections in a box of glass beads, which acted like a sandbox, to prop the pieces up. While the Paraloid B-72 dries, you want the join to be horizontal so that gravity helps keep the pieces in place. I then mounded up tissue for a support when I put the rim sections together.

Left: sections of the rim standing in glass beads; Right: the completed rim.

I put on as many pieces as possible, but then it became hard to place the pieces exactly. I then switched to gluing the small slivers together to create larger pieces. The center is mainly intact, but there are only a few places where a sherd touched both rim and center, and none of those had good join edges. 

Small sherds grouped into larger pieces, drying against a weight.

Claudia called Stephen Koob, a ceramics conservator at the Freer who has written books and articles on ceramic reconstruction methods. He said that he has seen a Seljuk bowl with laminated pieces, though not as bad as mine. It could be as issue with a particular clay or firing. He suggested using a synthetic material called Flügger to gap fill. Flügger is like plaster, but it is more flexible and stays workable for longer. It is used more in Europe than in the States, though it started to be used fairly recently.

To cast the bowl properly, all the joins had to be perfect and the angle of the sherds correct. I decided the best way to do this was to break up the rim into six sections and fix each before putting them back together. I used acetone to dissolve the worst rim joins, then I used a hairdryer to heat up the thermoplastic adhesive on each join to manipulate the pieces back into shape. I also heated and fixed the joins on the smaller interior pieces.

I made a new support for the bowl out of carved foam, cotton, and tissue. I used a razor and scalpels to carve out the general shape of the bowl from the pieces of thick foam. I cut a large depression in the middle so that the top of the base was level with the sides of the bowl. This was padded with cotton, then a sheet of tissue was placed over top.

Carving the foam.

I nestled the pieces into the support and pinned them in place. The central section was quite stable, but it took some work to get the rest of the ceramic to fit. I left off the top pieces of laminated sherds. When they lay over a back section, I cannot put the pins in place. The first time I tried to put all the rim and back pieces in, I was left with a centimeter-wide gap which I physically could not close. I took the pieces all off, padded the support again to change the angle of the sides slightly, then tried again. This time, I was able to close the gap and get all the pieces to fit. Although it is still not exact, the pinned pieces looked good.

Top: First attempt, with a large gap in the rim on the right; Bottom: Pieces pinned into the support.

Parthian Vessel Joining and Filling

After desalination and gentle cleaning of the Parthian vessel, the potsherd edges were sealed with a thin layer of a 10% solution of Paraloid B-72 in acetone. This is to prevent the stronger adhesive used to hold the pieces together from getting in the porous ceramic, and it helps remove that adhesive. If a piece was out of place, or in the future they needed to disassemble the vessel, it would be quite easy to do with a bit of acetone. The pieces were then joined with a 40% solution of Paraloid B-72.

For the most part, the pieces fit well, but the ceramic was thick and heavy. The bottom pieces slipped a little when I added the higher pieces, so I had to bandage the vessel and continually check to make sure the joins were correct. I also had to use more Paraloid B-72 to cover the entire edge. This meant that excess adhesive was squeezed out when the joins were very close. After it dried, I removed the excess adhesive with acetone-soaked cotton swabs.

Several gaps remain, particularly around the rim. The vessel could have had a spout at one point, which would have easily broken off. Fortunately, these holes are small and do not affect the structural stability of the vessel. Two of the pieces do not belong to this pot, both a slightly different color than this pot. One is made from a much lighter and more porous ceramic. The other is smoother and thinner. During the Seleucia excavation, they accidentally got placed with the wrong vessel.

It was decided that this would be a good pot to practice fills. The lowest large hole, irregularly shaped (visible in the top left and bottom right images), was chosen. I placed a piece of dental wax over the loss area inside the bowl to support the plaster during filling. To do this, I cut a square of wax, then heated it to make it workable. My hands were not warm enough, so I placed it in hot water. I could have also used a hair dryer if I wanted it even warmer and softer. I then placed it inside the vessel and pressed it into the ceramic. I pushed the edges of wax hard to stick to the rough ceramic to get a good seal around all the edges.

The vessel was then placed on its side so that the hole was horizontal. I then filled it with plaster made with deionized water. The dry plaster was added to some water until it started to mound up, then mixed until it reached the correct consistency. It needed to be wet enough to work with, but thick enough to build up, like frosting. I dabbed wet plaster into the loss along the edges and undercuts, where it might have been hard to fill if I had just poured the plaster. After the initial layer, I mounded up the plaster with a spatula. I needed to work fast as the plaster dried surprisingly quickly, and it was set before I finished placing all the plaster into the fill. Even so, my fill was fairly good, though a higher fill would have been preferable. It was just proud of the ceramic, but I could have mounded up more plaster. Its easier to take away excess plaster than it is to fill in depressions and pockets.

After drying overnight, I carved down the fill to the level of the vessel. I first used a flat spatula and scalpel. The plaster scraped away fairly easily, though it was a bit difficult getting to the same level across the entire fill. After I got down, I used sandpaper to smooth the plaster. I removed a little plaster around the edges of the fills to simulate cracks around a sherd. This undercutting also made the piece look better in the spot where the fill was too low. The plaster was then sealed with 20% Paraloid B-72.

I painted the plaster with watered down acrylic paint fill to blend in better. I made a small piece of plaster to test the colors on. I used titanium white, yellow ochre, raw sienna, burnt umber, and raw umber, trying to match the general beige color of the ceramic. I wanted it to match the background color so that it would not be jarring or distracting, but I wanted it to be very recognizable as a fake fill.

I used several layers, moving from lighter to darker shades. The first layers were very watery, to get the basic tone of the ceramic. Upper layers were more pigmented, to the correct shading. The first few layers did not stick well to the sealed plaster, so there were water marks and visible brush strokes, though these were covered in later layers applied with a dabbing motion. Because I did not mix up enough at first, I had to keep mixing the paints for each layer. This meant that some layers were slightly more yellow, others more grey. They created an effect that works well for this ceramic. I probably should have made the color a little lighter; it is easier to work up from a light base than cover a dark one. Suzanne also told me after the fact that acrylic paints often dry darker and cooler than when wet. Because the plaster was sealed in Paraloid B-72, I could wash off the paint with water and start over if it was needed. In the end, the fill had the same basic tone as the rest of the original ceramic, but it is clearly a fill.