The furnace door opened onto a wall of fire.
Iven had expected a glow. He had not expected the sudden white sheet that rolled over the lower lip and struck the shield in Dara’s hands. She staggered backward. He caught her by the shoulder and pulled her behind the brick screen as hot air rushed through the workshop.
“Shut the draft!” Kel shouted.
The apprentice at the draft wheel turned it hard. The wheel spun freely. Its connecting rod had come loose.
Iven seated boiler jacket, plate brace, spring step, winch draw, and heat exchanger. He pushed past the screen before the flame could spread to the drying rack. The jacket wrapped warmth around his torso, buying him a few seconds against the flash. He seized the draft lever directly, pulled it down, and held it until the furnace’s roar changed to a deep, uneven rumble.
Dara and Olin dragged the drying rack away from the door. Kel threw the outer damper shut. The fire receded into the chamber, leaving the brick face blackened and the air thick with smoke.
Iven stepped back behind the brick screen. Dara set the scorched shield on its blocks, and he used heat exchanger to move heat from that external metal into the heavy receiving block before letting the patterns quiet. His skin still felt hot beneath his coat. He checked his sleeves and found one singed edge but no burning cloth.
