Issue link: https://digital.copcomm.com/i/77744
n n n n Scanning The scan data was im- ported into Geomagic's Studio, where a color- coded error map graphi- cally showed the various gaps and stresses on the foot portion of the coffin. knew this [movement] was probable due to the way the wood had been assembled," she says. "But there were no other surprises or problems." In fact, soon after the object was acquired by the museum, an ultrasound and X-ray were done to reveal the density of the wood and to show voids and insecure areas. CT scans were considered, but no local scanning units were large enough for the job. This ini- tial imaging provided the team with a firm indication that there were areas of weakness or places where the wood might bend or move over time. According to Garland, it is the back section (with a number of defects) that is most concerning, not the much larger and top-heavy front. These tests also showed that the coffin was made up of various pieces of wood that are pinned together with wooden pegs—which is typical construction for this type of object since wood was scarce in Egypt. Unfortunate- ly, many of these shaped pieces of wood have separated, causing paint loss. well. As Garland points out, the construction has splits in the wood and gesso fills that are no longer flush with the surface, particularly in the shoulder and knee areas, indicating that significant movement of the wood had already occurred. "Voids are accompanied by patching, dowels (modern and original), and multiple pieces of wood, all of which represent potential areas of instability," she explains. "However, none of these areas are part of the load-bearing structure. The load would primarily be born down the sides of the figure and concentrate on the feet, which appear to be structurally sound." More concerning was the split in the center of the main load-bearing wood that follows This issue was detected in the digital scan as 38 June/July 2012 the wood grain: Splits and checking such as this significantly reduce the structural integ- rity of the wood. As the weight of the coffin is shifted during reorientation to a vertical posi- tion, a force bearing down on the tip of a split will be distributed over the split's surface since the interior of the crack is not able to support any weight and resolution of the forces over the surface will cause the split to open. In ad- dition, the top of the split is cut off at a saw cut (which occurred prior to the museum's ac- quisitioning), making it easier for the forces to pull the split open, thus weakening the struc- ture over time. The early imaging, as well as the more re- cent digital scanning, delivered some good news: Despite its age, the coffin was in great shape. the group at the Nelson-Atkins Museum of Art hired a structural engineer to design a mount—no easy task, considering that the priceless object could not be physically altered in any way in order to attach it to the arma- ture, nor could the mount be enduring despite the fact that the exhibit itself is permanent. "We have to be sure that anything we do can be undone," Garland says. "We spent a long time evaluating how to do the mount that would hold the coffin in place. The scans were also useful for this purpose." Today, the mount is holding the coffin up- right, but it is tilted slightly backward about five degrees, thus easing the downward stress exerted on the wood of this fragile artifact since the force is distributed over the surface along the foot rather than being concentrated only at the front. Inclining the bottom section also reduces the stresses on the load-bearing crack in the bottom center since the forces are shifted toward the back. "The ultrasound showed that ideally [the 400-pound coffin] should be presented flat. But there was a strong sense within the mu- seum that we wanted a very powerful effect [in the presentation]," says Garland. "We also had so many beautiful accoutrements and objects that we wanted to display within this small space, which was another reason why we wanted to show [the coffin] upright." Display Decision Before the museum could make a final deter- mination as to how the coffin would be dis- played, some preliminary work had to be done on the coffin. As Garland explains, the flaking paint had to be consolidated since the results would have an effect on the orientation of the mount. If the paint could not be satisfactorily reattached without altering the appearance of the matte paint, then the inner coffin would not be displayed upright. Once that had been accomplished and with the scan data backing up their decision, This tilted position will also help preserve the paint on the wooden surfaces. "Egyptian paint is very fragile and delicate, and we didn't want to lose any more of it due to movement in the wood [because of how it was posi- tioned]," says Garland. Despite having the digital data to help allay their fears, Garland nevertheless was nervous when it came to lifting the coffin into its new display setting. "It was so nerve-racking lift- ing that piece up. We didn't know if the coffin and the wood structure would be damaged, if it would collapse," she says. "We were pretty sure it would be fine, but you just never know, and this stuff is irreplaceable." The placement went without a hitch, and today this beautiful object and the rest of the assemblage of Meret-it-es' funerary objects are on public display in the new museum wing. And should the museum opt to do so, the digital data from the scan can be turned into a realistic, interactive 3D model that, unlike the actual artifact, can be handled without worry. Meanwhile, the long-term effects of re- orienting the coffin may not be known for a long time. Indeed, there was no structural shifting during the vertical placement, but it is difficult to predict with accuracy how the ancient wood will hold up over time, contends Garland. But with digital methods, the mu- seum will be able to continually check on this millennia-old treasure to safeguard it well into the future. n Karen Moltenbrey is the chief editor of Computer Graphics World.