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It’s the thrill of victory as Kentaro Kojima splits a 500-pound granite boulder as intended with hardened-steel wedge

Sculptor Kentaro Kojima speaks Japanese, Spanish and English.

He also speaks to stones, though he’s still waiting for a reply.

“I’m trying to talk to them often. But, they don’t engage me just yet.”

Master stone masons say they can listen to these great granite boulders and be told where to use hardened-steel wedges to efficiently split rock.

The wedges are called “jumping arrows” because they wind up under great forces “being squeezed. If you mess up it jumps out of the stone.”

Kojima, who manages the fabrication area at the Marenakos Rock Center in Issaquah, is still learning; he took a workshop four years ago from two Japanese masters.

He approaches 500 pounds of high Cascades granite with chisels, wedges and an 8-pound sledge.

First he draws a line across the boulder. Then he works small holes into the boulder along the line where he’ll insert the wedges.

Next, it’s bam, bam, bam with the sledge.

In 30 minutes the stone slowly fissures as the first cracking sounds emerge.

He keeps tapping the five steel wedges in sequence.

Splitting sounds increase, and the boulder divides as intended.

Kojima spreads his arms in delight.

“It’s a visceral excitement. Your inner caveman comes out.”

This August two 14th- and 15th-generation master masons from Japan will come to Kubota Garden to lead a workshop. Kojima will assist and translate while a base with 300 tons of stone is built for a terrace overlook.


Kojima taps the steel wedges, called “jumping arrows,” into the boulder with an 8-pound sledge.

For more photos, visit the gallery.