Wading Village.
Su Li crouched in front of Old Buck's furnace and studied it for a full five minutes.
Three cracks had already split the inner wall of the firebox. The bellows' leather bag was leaking air, and the angle of the air inlet was off by at least fifteen degrees.
The only reason this wreck of a furnace had lasted until now was Old Buck's thirty years of experience forcibly holding it together.
"Uncle, this furnace of yours needs replacing."
Old Buck was sharpening a hoe without even looking up.
"Replace what? It's been in use for twelve years and it's still good."
"There are three cracks in the inner wall. The fire temperature can't rise, so the iron you forge has uneven carbon content." Su Li stood and dusted off his hands. "I'll modify it for you."
Only then did Old Buck raise his head and eye him sideways.
"You know how to fix furnaces too?"
"Not fix. Modify." Su Li picked up a twig from the ground, crouched down, and sketched a rough diagram. "Adjust the air inlet to forty-five degrees, coat the firebox's inner wall with a new layer of refractory clay, replace the bellows with a new leather bag, then add a small secondary air inlet."
Old Buck set down his hoe and came over to look at the drawing on the ground.
He stared at it for a while, his brows knitting tighter and tighter.
"What does this secondary air inlet do?"
"It lets air enter the firebox from two directions. The flames will burn more evenly, and the temperature can go up by twenty percent."
Old Buck crouched down and traced the diagram with a finger.
"...Where did you learn this?"
"Back when I was wandering around, I saw a dwarf blacksmith using