Ezra arrived at the yard in the outer ring, setting his sights on the blast furnace.
For three weeks, the blast furnace had dictated the lives of the men working around it. The heavy thud of the waterwheel, the rhythmic clack of the wooden cams, and the deep, continuous roar of the air blast had become the heartbeat of the smithing district.
The laborers worked in three shifts. Carts of ore, crushed limestone, and charcoal arrived from the quarry road. Worker upon worker hauled the materials up the spiraling timber scaffolding in wheelbarrows, tipping them into the open mouth of the thirty-foot stone tower in precise ratios.
Today, he was supposedly just doing a routine check before leaving everything to Arran and Halvork.
"Lord Ezra," Arran bowed, while Dynham eyed him with disdain. Dynham hadn't gotten over Arran disrespecting Ezra during the time when Arran and Ezra were first acquainted.
"How goes the kiln, Master Smith Arran?" Ezra asked.
"I have been tallying yields ever since the kiln's first firing," Arran said, smacking his lips. He held a notebook that was issued by the press.
"But ever since the day after Lord Blackfyre's visit, there has been a slight decrease in yields," Arran continued, flipping the notebook to check the dates he had written.
"At first I paid it no mind. I had thought that the ore deliveries had stalled. After all, there should be minor changes in yield from time to time. It will never be exact. But yesterday, the difference between pours had been too obvious."
"Watch, Lord Ezra. Another pour is going now."
A worker stood by the taphole with a heavy iron bar. A laborer swung a mallet, striking the back of the rod twice. The baked clay plug cracked and shattered inward.
The iron oozed outward, but something was off. Ezra used AMP to check. The viscosity and volume of the pour were significantly different from the first batch. Even though Ezra didn't have an eidetic memory by default in this life, as long as he channeled mana, his mind functioned in much the same way. The only nuance was focus: a regular recollection naturally retrieved whatever was most important to him at the time, while recalling exact, minute details required a much harder mental push involving mana.
The pour had been significantly off the mark. After the whole casting process finished and the liquid fire settled, Ezra looked at the sand bed. A third of the rectangular "pig" molds remained completely empty. The total volume was barely three-fourths of their first successful batch.
"Have you checked everything, Master Smith?" Ezra mused as he furrowed his brows. He started to walk with Arran.
"I did, Lord Ezra," he said gruffly, though the confusion was in his voice. "Come, I'll show you, Lord Ezra."
Ezra came with him.
"I asked Halvork and he helped me inspect the workings after the slag drained," Arran said. "He isn't here right now. He needed some rest."
Ezra nodded.
"We started with the tuyeres," Arran said, leading Ezra around the curved stone base of the tower.
The heat rolled off the stone, but Arran didn't seem to notice. He stopped and slapped his hand against one of the iron pipes feeding into the hearth. "I thought the air was leaking before it hit the lower fire. But look here, Lord Ezra. The clay packing is baked hard. No air escapes."
They continued down the slight slope toward the riverbank.
Arran stepped over the dirt path and knocked his knuckles against the timber housing of the bellows. "We thought that it might be the waterwheel. But we checked the wheel. The bellows are still pushing." Arran pointed down to a heavy wooden fitting near the water. "See this? The wheel turns fine, night and day. All the rivets, fittings, and furnishings are intact."
Arran cleared his throat. His face tried to hide his distaste for the next words, but the color in his cheeks showed.
"We even had Maester Draffen bring a carpenter and craftsman to check the whole wheel while it was still turning. There wasn't anything they found broken."
He wiped a hand on his heavy leather apron, turning to lead Ezra back up the slope toward the casting floor. "So Halvork and I tried to check more things. I told him the belly must be losing heat. But we checked the masonry."
Arran stopped inches from the tower's base, gesturing to the white-hot mortar between the massive stone blocks. "Even if you throw a cup of water on the lower blocks, it turns to steam before it can even run down the stone. The mortar is sealed tight. We aren't leaking any heat through the cracks."
Arran walked a few steps closer to the iron pipes, his voice raising slightly to cut through the roar of the air blast. "Then we checked the fire itself. Halvork stood watch by the chimney. He said the flame out the top still burns white. No orange, no thick black smoke. The charcoal is burning clean."
He tapped the thick pipe again. "I even looked through the gap here when the bellows pulled back. The glow inside is still bright. And when we tapped the upper hole after, the slag ran the same—still clear. It didn't clump or drag; it still ran fast."
He paced away from the tower, his heavy boots crunching loudly over the dirt. "So I thought the haulers had grown lazy and lessened the load. I counted the ledger marks twice. Three barrows of rock, one of lime, three of charcoal. The counts are the same. The men put the right load into the top."
They reached the edge of the waste pits. A strong smell attacked Ezra's nose; he used mana to somehow tolerate it. "I thought the iron might have run high or somehow got poured out the wrong hole. I took an iron rake to the pits once they cooled. I smashed it apart. It was just rock and ash. There are no heavy chunks of iron hiding in the waste dirt."
He turned back, staring at the plugged hole at the base of the furnace. He rolled his heavy shoulders, mimicking the motion of a man driving a pike. "Before Halvork plugged the bottom hole for the next round, I took a ten-foot iron rod. I drove it straight into the lower hearth. I dragged it across the floor of the belly. I thought the metal might have frozen. But the bar hit nothing but liquid and flat brick. The iron is not stuck inside."
Arran crossed his thick arms, standing still amidst the noise and the heat. He stared up at the towering stone structure.
"The masonry is hot. The air pushes. The tallies are exact. The belly is clear. The machine does exactly what it was built to do."
He made a guttural sound in his throat. "But the iron is still short."
As Arran toured him around the whole blast furnace, he had AMP activated the whole time. Ezra had been practicing reinforcement on his body, with the knowledge of which muscles, nerves, and veins to push mana toward. He could use reinforcement to actually zoom in on the minute details that Arran was pointing to.
He could even tell the temperature of the molten iron from afar. So far, everything Arran said checked out.
"We are still using the same ratios? I mean, the same amount of limestone for each barrow of the ore?"
Arran nodded. "Aye, it never changed."
Ezra huffed. The symptoms that the blast furnace was currently suffering had a name on Earth.
A salamander.
When the chemistry of a blast furnace was thrown off, the iron didn't just vanish. It cooled and froze at the very bottom of the hearth, forming a massive, dead block of solid metal that slowly grew upward. If it wasn't melted out, the "salamander" would eventually choke the belly and permanently destroy the furnace.
"Master Smith," Ezra said, his voice suddenly sharp. "When you put the iron rod into the lower hearth to check if the metal had clogged... did the rod hit the bottom at the exact same depth as our first batch?"
Arran blinked, caught off guard by the specific question. His brow furrowed as his memory replayed the sensation of the rod hitting the floor.
"I... I wasn't sure, Milord," Arran muttered. "The slag is freezing there, isn't it?"
"That is what it looks like," Ezra nodded. "You aren't scraping anything because it's already frozen there. That wasn't brick your stick touched."
Arran clicked his tongue.
"I'll get Halvork. We need to deal with this somehow," Arran muttered to himself more than to Ezra.
"We need to melt the dead slag," Arran rumbled, his hands gripping his apron. "That frozen lump is going to damage the kiln."
"We need to understand why this is happening, though," Ezra said to Arran. "If the ratios never change, then there must be something I am missing."
Arran nodded. "Milord, I'll send word to Halvork. I will try to fix this."
He bowed once and went to fetch a messenger.
What am I missing? What am I missing? Ezra walked back, lost in thought. He traced his steps from the output back to the bellows, to the waterwheel, and then finally to the mouth.
A constant rhythm of workers kept hauling the ores and the limestone one after the other. His eyes followed the line of men that kept pushing the wheelbarrows.
There was just something odd. Out of every five people hauling ore, one was coming from a different direction. This bothered Ezra for some reason.
"Mister," Ezra faced the foreman. The man nervously shuddered at the address.
He bowed deeper than what was normally expected. It seemed that he didn't expect to be talked to by Ezra.
"Sire," the man replied.
"Why is it that out of every five workers hauling the ore, one comes from over there?" Ezra pointed to his left.
"Ahh, my lord. You see, the daily carts from Craggy Rook haven't changed. The writs for the quarry haven't been redrawn yet to match what we need now. Maester Draffen told us that since the new blast furnace eats through a load much faster than the old bloomeries, they had to buy the rest off the river merchants to keep the wheel turning."
Ezra eyed the incoming wheelbarrows of ore.
"I need them to hold it first."
"Sire?"
"I need them to check something. Get a barrow of the ore from the rook, and one of the barrows we bought from the merchants. Have the workers wash the dirt off them."
The foreman stared at Ezra, trying to decipher the command.
"Wash the mud off," Ezra clarified. "Just put them in separate basins when you finish. I want to see."
The foreman scratched his head, then obliged. He knew better than to question Ezra, who had even been giving suggestions to Arran.
When everything was prepared, Ezra had them stand the basins side by side.
Ezra activated AMP. With the mud and loose dirt washed away, he clearly saw the discrepancy. The volume of dense, usable iron in the merchant's basin was significantly lower. The rock itself was poorer quality. Ezra had a hunch the Craggy Rook ore was being pre-processed or sorted in the mines by the Blackfyre workers, whereas the merchants just scooped up whatever heavy rock they could find to make weight.
"Alright. Thank you."
Ezra left the workers bewildered.
When Arran came back with Halvork, Ezra greeted them. "Master Smith, Kilnmaster."
They bowed in acknowledgment. "I think I found the source of the dead slag."
"Oh?" Arran breathed as he raised an eyebrow.
"It is because the ore of the merchants isn't as good as the one from Craggy Rook."
Arran clicked his tongue. "I told Maester Draffen not to buy bad ore from those conmen. I had a feeling that something would happen. I just couldn't point out what. Now we have a furnace eating itself from the inside."
Halvork opened his mouth. "As for the dead slag, I think we can make the hearth hotter than it currently is; then, we can melt the frozen iron. If we make the bellows run faster, that would make the kiln much hotter."
Ezra nodded.
"That means we should also put a blank charge, aye?" asked Arran as he faced Halvork.
"Yes. If we only load coal and lime, then the slurry would be enough to clean the slag below."
"I think in the future, if we see that the slag starts to thicken to something dark," Ezra suggested, "then we should probably add an extra barrow of limestone on the next load."
Arran tilted his head and thought about it. Then he nodded. "Aye, we check if the slag runs, and add more limestone if it doesn't. We just have to tell the other shifts after we clear this run."
"Aye, the slag must flow," Halvork said.
Lisan al gaib. Ezra thought.