The bowls were cleared and the fire in the salt-kiln had settled into a steady bed of cherry-red coals. Then, the final task of restoration began.
Qiao Ming brought his animal fat lantern to the center of the black walnut table, adjusting the hemp wick until the flame cast a clear, steady beam of golden light across the stone surface.
Beside the lantern, Yan Zhiqiu laid the Broken Slate.
The tablet was clean of surface mud, but in the tiny grooves of the intaglio relief, a stubborn, stone-hard crust of ancient blood-scabs, stone-hardened quartz dust, and dried void-ozone still obscured the finest lines of the engraving. To read the full stone-built blueprint of the Nadir, those tiny channels had to be cleared with clean, steady care.
From his tool drawer, Qiao Ming retrieved two specific implements. A square of cured sharkskin, its surface covered in tiny, diamond-hard placoid scales that acted as a gentle, non-destructive emery paper. A small clay pot of fermented plum vinegar, whose mild natural acid could dissolve hardened stone crusts without etching the dense black shale beneath.
“We must work with the grain of the incisions,” Qiao Ming said, his voice quiet in the warm stillness of the room. “The sharkskin will level the crust without dulling the corners of the characters. But if you press too hard, the shale will flake along its cleavage planes.”
