This is a three-part series exploring art restoration at Yale as the Yale University Art Gallery’s ongoing renovation provides increasing gallery space for the University’s more than 185,000 permanent collection pieces. Part 1 investigates the process of bringing art out of storage through the lens of the nineteenth-century Huntington murals. Part 2 probes the innovative techniques used and created by Yale conservators during the restoration of works like a fragmented sixth-century Byzantine mosaic found in the 1930s. Part 3 considers the art that conservation forgot.

At the A21 building on West Campus, five pieces of a sixth-century Byzantine mosaic lean against wooden supports under the fluorescent lights of an industrial workshop. Jazz music plays on the stereo as Thomas Philips, the senior materials assistant at the Yale University Art Gallery, prepares to grind a layer of concrete off the backs of the tiled works, which were excavated in the 1930s from Gerasa, now present-day Jerash, Jordan.

The modified concrete cutting and mounting techniques that will be used in the restoration of the mosaic demonstrate some of the ways in which the Yale University Art Gallery’s conservation department is employing innovative technologies to restore a number of artworks coming out of storage for the collection’s reinstallation in the renovated wing of the gallery. For projects like the Gerasa mosaic, conservators are experimenting with materials from the airplane and marine industries to construct sturdy backings, and for the first time ever they are modifying computer-controlled industrial cutters for use in art restoration.

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On West Campus, Philips breaks through the concrete using a Computer Numeric Control tool, a machine about the size and shape of a pool table with a computer-controlled drill bit attached to a bar that hovers a few feet above the table at one end. The common woodshop device is not a tool typically used for art conservation, but a few modifications on Philips’ part have repurposed the machine.

“What we’re really doing is taking technologies that have been proven in other fields and applying them in new combinations to solve this problem,” said Daniel Morrissey, a structural engineer from Deep River, Conn., who joined the conservation team to help decide how best to mount the mosaics in the renovated gallery.

The concrete was added to the mosaic by Yale conservators in 1933 as a standard conservation practice of the day, but when the heavy backing began to damage the work and make it too heavy to hang on the art gallery’s walls, the mosaic was put back in storage. Art gallery object conservator Carol Snow said the gallery had plans to have conservators at the Getty restore the mosaics for years before she came to Yale in September 2008, but the decision was made to instead restore the work on Yale’s campus, beginning in summer 2009. When the backing is removed and lighter supports made of industrial materials are attached, the mosaics will be mounted as part of the reinstallation in the Swartwout Sculpture Hall, one of the art gallery’s spaces that is currently under renovation.

Figuring out how to employ the computer-controlled cutter to restore the artwork has been challenging, Philips said, especially in a field where each project presents unique and unexpected challenges.

“The technology’s been around for a while,” Snow said. “But the new application for museum use is what we see as cutting-edge.”


But cutting-edge technology does not always mean expensive, custom-made machinery.

The art gallery purchased the Computer Numeric Control machine on a low-cost personal robotics website called ShopBot for $35,000, which Philips said is a reasonably small investment for a museum given its multiple applications.

Though the cutter was purchased with this concrete removal endeavor in mind, its versatility makes the cutter useful in conservation, Philips said. The department also has a smaller computer-controlled cutter, that measures 4 by 4 feet and cost $10,000, which Philips previously used to cut custom cavities in foam blocks for the transportation of a sculpture to the National Portrait Gallery in London. According to the ShopBot website, the machines purchased by the gallery can be used to produce everything from tombstones to sailboat parts to aluminum sculptures.

“You can stay nimble,” Philips said. “You can run it with a plasma cutter if you want to cut sheet metal. You can run it with all kinds of bits for cutting wood. Almost any kind of metal, you do just fine with it.”

Philips has a lot of practical experience in “making things work.” His background is in carpentry, and he has built his own windsurfing boards. These skills are put to use while he is toggling with the cutter, swapping out motors and bits to best fit the needs of the mosaic project.

There is no guidebook for cutting concrete off the backs of ancient mosaics, so putting the cutter to use on these pieces has required a great deal of tuning and experimentation, he said.

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“I just go by guesswork, by the seat of my pants,” he said. “As a result, we’ve been able to tune it up and dramatically improve it.”

These improvements included the purchase of a new motor — the previous one was too fast and quickly wore the drill bits out — and ordering custom bits for an extra-deep cut. Philips also had to toy with the speed and rotation of the cutter to determine the optimal pace for the mosaics project.

“When you cut known materials with conventional methods, there are tables for these things,” he said. Not so for projects involving thousand-year-old mosaics.

Philips is also in the process of experimenting with the computer-controlled cutter to replicate missing sections of an architectural woodwork by American designer Lockwood de Forest that is owned by the gallery. Attaching a probe to the machine, Philips can generate on a computer a three-dimensional image of an existing piece of the teak carving; when the probe is swapped out for a cutting tool, the machine can chisel the same pattern into a new piece of wood.

For now, this is just a test to see how well the cutter can duplicate the de Forest woodwork. If the results are good enough, Philips said the curator may decide to incorporate the manufactured pieces into the reinstalled work.

It is all a matter of having time to tinker with the cutter.


But the going is slow on the mosaic’s concrete removal.

Using the cutter requires caution: When Yale’s lab conserved the mosaics in 1933, the team added a reinforcing steel frame into the concrete. While cutting the backing away, it is important to map out where these bars are, Snow said, as hitting the steel with the tool bit could send shrapnel flying across the lab.

Human casualties caused by rogue shards aside, removing the concrete and steel without damaging the mosaic requires care and attention. Philips said he will likely be able to grind the concrete down to within a one-quarter to one-sixteenth of an inch of the mosaic’s original backing, though that aim is made complicated by the piece’s uneven tiling. Fortunately, the computer-controlled nature of the cutter reduces some of the risk of human slipups.

“That’s one of the beauties of the CNC,” he said, “We can control the bit within one-thousandth of an inch with a computer. You can be more confident that you’re not going to slip. You can go slowly and work your way down to it.”

Philips cannot go too slowly, though, as he is largely the only one of a shorthanded department who can operate the machine. He estimated that he could get through about 16 square feet of concrete in 24 hours — but three of the five pieces are four times that size and Philips is working on a number of other conservation projects at the same time. The mosaic will take at least another three months to complete, he said.


When the mosaics are reinstalled in Swartwout Sculpture Hall in 2012, they will be mounted near to where they hung for 10 years in the 1930s. But before that can happen, the conservation team needs to figure out how to get them up there.

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Like the concrete cutting process, this portion of the mosaics’ restoration also involves reconfiguring existing technologies and materials to retrofit the pieces’ backings. Morrissey said that while the team will use conventional methods to secure the mosaic to the gallery wall, the backing that will replace the concrete will be made of more experimental materials, as it must be both lightweight and extremely strong. The newly backed mosaics will weigh about a fifth of what they did with the concrete backing, Snow said, which caused the pieces to clock in at nearly 1,800 pounds.

The conservation team will likely use a resin adhesive to attach two layers of fiberglass separated by a foam core to the back of the mosaic pieces, Morrissey said. The new backing will then fasten onto the wall. The team is looking into materials similar to those used in building boats, like fiberglass, carbon fiber and Kevlar, because of their strength and light weight.

In borrowing materials from the aircraft industry, marine technology and wind turbine construction, this project will help the conservation team continue to repurpose existing technologies for art restoration. This mosaic will bring experimental techniques to a renovated gallery full of traditionally conserved pieces.

But none of this — the application of a new backing, the concrete cutting — can happen just yet. Philips has taken a weeklong break from the Gerasa mosaics while he waits for the new motor to come in.

For the final installment of this three-part series — a look at art that cannot be conserved — see tomorrow’s News.