But he and fellow Washington National Cathedral stone carver Andy Uhl seldom wear gloves.
Inside their shop, which is littered with pieces of earthquake-damaged limestone, the gloves are stashed atop a storage cabinet.
For this work, Callahan, 46, and Uhl, 48, need their bare hands — to feel the stone, steer the power chisel, and hold the thin files and tools they use like an artist does a brush.
Earlier this month, the men said they had begun the massive job of fixing or replacing the dozens of finials, crockets, angels, cherubs and gargoyles that were damaged in the Aug. 23 earthquake.
When the 5.8-magnitude quake hit, it shook the giant English Gothic cathedral like a stack of blocks, knocking off many decorative elements, which tumbled to the ground or smashed into other sculptures, damaging them, too.
Some are broken beyond repair and must be replaced. Others, like those in the shop in the cathedral complex on Wisconsin Avenue in Northwest Washington, can be repaired.
“We’re going to fix as many of the original stones as possible,” Uhl said recently. “There are some we’re not going to be able to fix.”
The cathedral has said it needs $15 million for the initial repairs and millions more for full restoration, which could take a decade to complete.
Replacements will be carved from stone acquired from the same Indiana quarry where the cathedral’s original stone was cut, the men said.
As Uhl spoke, two damaged “crocket stones” — rough and gray from time and exposure — rested on separate turntables to undergo repair. The 300-pound stones, the first to be fixed, are so called because they include decorative elements called crockets, which are outcroppings carved to resemble flower petals, leaves or stems.
Limestone weighs about 150 pounds per cubic foot.
The cinder-block shop was filled with metal storage closets, shelves of instruments that looked something like heavy-duty dental tools, exquisite stone decorations and a softball-sized cherub’s head.
Uhl said the carvers’ work is much like dentistry: The goal is to replace damage while maintaining as much of the original stone as possible.
Much inside the shop, including the carvers’ hands and arms, was covered with the fine, cream-colored powder that blows off the stone during repairs.
The walls were hung with diagrams and some of the original blueprints of the cathedral.
Callahan was crafting a patch, or “dutchman,” to replace a broken part of one stone. To do so, he cut out the damaged part and prepared a blank piece of stone from the shop’s spares to insert in its place. He will carve the “blank” to match the decoration on the stone.
Limestone, which starts out smooth but develops an extremely coarse surface over time, is exquisite carving material, Uhl said.
“It’s a great medium,” he said. “It has a fine grain to it, so you can carve it from many different directions . . . [and] it has a warmer tone.”
The carvers use tools as potent as a diamond-tipped saw and as delicate as a pencil-size file to re-create in stone the veins in a leaf or the eyes and nostrils of a cherub. If the men don’t have the right tool, they said, they can make it.
All of this builds robust hands. “The little muscles in your hands get very developed,” Uhl said.
“You get fat fingers,” Callahan said.
But protective gloves are mostly out.
“With the air hammers . . . you lose dexterity” if you use gloves, Callahan said. “You like to feel the tool in your hand. . . . I like to feel the chisel.”
Gloves, the carvers said, are used for cleaning out the cathedral’s roof gutters.