Chapter 7: The Master Alloy

The morning after the first cast, the sand beds of the courtyard held thirty
heavy, dark gray bars of pig iron. They looked like rough, dirty stone, their
surfaces blistered with white patches of sand and glassy slag.

Amine stood over them, a heavy iron sledgehammer in his hands. He raised the
hammer and swung it down with all his strength onto the center of one of the
cold bars.

With a sharp, dry crack, the thick iron bar snapped in two.

Lounes bent down, picking up one of the broken pieces. He peered closely at the
fractured surface. It was a dark, sparkling gray, made of millions of tiny,
crystalline facets that caught the weak winter sun.

"It is dry, Sidi," Lounes said, rubbing his thumb over the sharp crystals. "It
breaks like cold tallow. A horse-shoe made of this would shatter the first time
the beast trod on a cobblestone."

"Because it is full of carbon, Lounes," Amine said, leaning on the handle of his
sledgehammer. "The iron drank too much from the charcoal during its descent
through the furnace. It has nearly four parts of carbon in a hundred. To make
steel, we must strip that carbon away."

"And how do we burn out what the fire has already put in?" Lounes asked, his
brow furrowing. "Do we melt it again?"

"We do," Amine said. "But in two different ways. First, we must take some of
this pig iron and burn the carbon out completely to make soft, pure wrought
iron. Then, we will mix that soft iron with a precise amount of this brittle pig
iron inside our graphite crucibles. The high carbon of the pig will dissolve
into the low carbon of the wrought, averaging out to exactly the ratio we need."

It was the Huntsman process—the classic crucible steel method that had made
Sheffield the steel capital of the world. By melting the two components together
in a sealed vessel, the carbon would distribute itself with absolute uniformity
through the molten mass, producing a homogeneous steel completely free of the
slag inclusions and soft pockets that plagued traditional "shear" or "damascus"
steel.

The first step was the "finery."

Inside the fort's old smithy, Amine had Lounes modify a traditional hearth. They
lined the deep stone basin with thick plates of cast iron they had poured during
the blast furnace run, creating a narrow, enclosed chamber.

A single copper tuyere, connected to the waterwheel bellows by a secondary
ox-hide pipe, was positioned to blow a strong, continuous stream of air downward
into the center of the hearth.

"We fill the hearth with charcoal, Lounes," Amine explained as Meziane piled the
black fuel into the basin. "We place the pig iron bars directly in front of the
air blast. When the charcoal burns, the excess oxygen from the bellows will
react with the carbon in the melting iron, turning it into carbon monoxide gas.
The iron will lose its carbon and turn into a pasty, semi-solid mass of pure
wrought iron."

It was a primitive but highly effective finery process.

For six hours, the smithy was filled with the acrid smell of burning iron and
the high-pitched hiss of the bellows. Lounes worked the hearth with a long,
heavy iron bar, constantly stirring the melting pig iron, lifting the pasty
clumps of decarburized metal into the path of the oxygen blast to burn away the
remaining carbon.

As the carbon left the iron, the melting point of the metal rose. The liquid pig
iron began to thicken, turning into a spongy, glowing ball of solid metal—the
"loupe."

"Pull it out!" Amine shouted.

Meziane and Yusuf seized a pair of heavy, long-handled iron tongs. Together,
they dragged the glowing, sixty-pound ball of spongy iron from the hearth,
dumping it onto a massive oak anvil that had been faced with a thick plate of
steel.

Lounes was ready. He swung a twenty-pound sledgehammer, his movements rhythmic
and powerful.

Thud. Splat. Thud. Splat.

With every blow, a shower of liquid slag and sparks erupted from the spongy
mass. The hammer blows compacted the iron, squeezing out the glassy waste
trapped in the pores of the metal, welding the crystalline grains of pure
wrought iron into a solid, dense bar.

"Again!" Lounes roared, his face blackened by soot, his muscles straining under
the wool of his shirt.

They worked the bar until it was flat, dense, and fibrous. When it cooled, it
was no longer the brittle, sparkling gray cast iron. It was a dull, smooth gray,
soft enough to be bent with a heavy hammer without breaking.

Wrought iron. Pure, low-carbon iron.

"Now," Amine said, standing in his private quarters before a crude balance scale
he had constructed from brass plates and fine iron wire. "We do the
mathematics."

Lounes and Meziane stood by the table, watching as Amine carefully placed small
pieces of the broken pig iron on one plate of the scale, and pieces of the soft
wrought iron on the other.

"If we want steel for rifle barrels and tools," Amine said, his fingers light as
he adjusted the weights, "the carbon content must be exactly eighty-hundredths
of a percent. If we use too much pig iron, the steel will be hard but brittle.
If we use too much wrought iron, it will be soft and will wear away under the
friction of the gunpowder."

He looked at Lounes. "For every ten pounds of the soft wrought iron, we must add
exactly two and a half pounds of the brittle pig iron. No more, no less."

Lounes stared at the balance scale. "And this... this tiny weight of the black
iron will change the whole mass?"

"It will dissolve into it like sugar into tea," Amine said.

He began to pack the weighed charges into one of their newly fired graphite-clay
crucibles. He layered them carefully: the soft wrought iron at the bottom, the
brittle pig iron on top, and a small handful of crushed oak leaves and charcoal
dust at the very top to create a reducing atmosphere that would prevent any
oxygen from entering the vessel.

Finally, he sealed the top of the crucible with a thick, tapered lid of the same
graphite-clay mixture, plastering the joint with wet kaolin paste to make it
completely airtight.

"We have ten crucibles ready," Amine said, turning to Yusuf. "Is the crucible
kiln dry?"

"It is, Sidi," the sergeant replied. "The men have been hauling the dense oak
wood all morning. We have enough fuel to melt the mountain if you wish."

The crucible kiln was a different structure from the massive blast furnace. It
was a subterranean furnace—a "pot-melt" kiln—built into the dirt floor of the
casting house to conserve heat. It consisted of two deep, brick-lined pits, each
capable of holding five crucibles, connected to a tall chimney-flue that created
a powerful natural draft.

The crucibles were lowered into the cold pits using long, scissor-like tongs
suspended from a wooden derrick. They were placed directly onto small pedestal
blocks of firebrick to keep them off the floor, and the space around them was
packed tight with hard, dense coke—coal that had been pre-burned to remove the
volatile gases, leaving pure carbon that burned with a intense, smokeless heat.

"Light the coke," Amine ordered.

They dropped glowing coals into the pits, and the natural draft of the chimney
caught the fire.

Within an hour, the pits were two roaring wells of white heat. The temperature
required to melt steel was far higher than that of cast iron—nearly 1,450
degrees Celsius. At this temperature, the air above the pits did not merely
shimmer; it vibrated with a dizzying, violet light that made the eyes ache.

Amine stood back, his face shielded by a wet wool cloth. He watched the chimney.
The draft was so intense that the bricks of the flue were beginning to glow a
dull red on the outside.

For four hours, they kept the pits filled with coke. Inside the sealed
crucibles, a quiet, invisible miracle was occurring. The soft wrought iron and
the brittle pig iron were melting, their atoms sliding past one another, the
carbon diffusing through the liquid mass until the mixture was perfectly
uniform.

"The bubbles have stopped," Lounes said, looking through a small piece of dark,
green glass Amine had sourced from a merchant in Algiers to protect his eyes.
"The liquid is flat as oil, Sidi. It is ready."

"Prepare the mold," Amine said.

Instead of sand, Amine had Lounes cast a series of heavy, split-iron molds from
the blast furnace run. Sand molds were too rough for steel; they would introduce
silica particles into the surface of the ingot, creating cracks during forging.
The iron molds were coated on the inside with a thin layer of soot from an oil
lamp to prevent the molten steel from welding itself to the cold iron walls.

"Yusuf, Meziane—take the derrick," Amine ordered.

The two men seized the ropes of the wooden derrick. Lounes took the long, heavy
crucible tongs, his arms wrapped in wet wool rags to protect them from the
blistering heat.

He stepped over the open pit.

The heat that rose from the well was terrifying. Lounes lowered the tongs into
the white-hot light, his teeth clenched, his eyes watering despite the green
glass. He clamped the jaws of the tongs around the neck of the first crucible.

"Hoist!" Lounes roared.

Yusuf and Meziane pulled.

Slowly, the graphite crucible rose from the pit. It was no longer black; it was
a brilliant, incandescent yellow-white, glowing so brightly that it cast no
shadow in the sunlit room. The liquid steel inside was visible through the
semi-translucent walls of the clay vessel.

Lounes swung the derrick, positioning the glowing crucible over the iron ingot
mold.

"Pour it slowly," Amine warned. "Do not let the stream touch the sides of the
mold."

Lounes tilted the crucible.

A stream of liquid steel began to flow.

Unlike the sparking, violent flow of the cast iron, the steel was quiet, smooth,
and had the consistency of thick cream. It was a brilliant, pale green-white,
glowing with an intensity that made the surrounding room look like a dark cave.
As it filled the iron mold, it hissed softly, a few tiny blue sparks dancing on
the surface of the metal.

They poured all ten crucibles, one after the other, filling the iron molds to
the brim.

Two hours later, the molds were unbolted.

The steel ingots slid out onto the earthen floor. They were long, square bars,
about forty centimeters in length, their surfaces a smooth, dull, blue-gray.
They looked unremarkable, but to Amine's eyes, they were beautiful.

He picked up one of the cooled bars. It was incredibly heavy, dense, and had a
ring when struck that was higher and clearer than any metal they had yet
produced.

"Let us test it," Amine said, carrying the bar to the smithy.

Lounes placed the steel ingot into the charcoal forge, heating it until it was a
bright, cherry-red. He drew it out and began to hammer it.

The metal was different from the soft wrought iron. It was stubborn, resisting
the hammer blows with a springy toughness that required all of Lounes's strength
to deform. But it did not crack. It did not scale or split at the edges. It
yielded slowly, turning into a long, thin wedge.

Lounes worked the metal until he had forged a thick, flat chisel. He quenched it
in a tub of oil—not water, to prevent the high-carbon steel from cracking—and
then tempered it by heating it gently in the embers until the blue scale turned
to a pale, straw-gold color.

He took the finished steel chisel and positioned the point against a thick bar
of raw, unrefined Turkish wrought iron they had taken from the fort's old
stores.

"Strike it, Lounes," Amine said.

Lounes raised a heavy four-pound hammer and brought it down with all his
strength onto the head of the steel chisel.

With a sharp, ringing clink, the steel chisel bit deep into the wrought iron
bar, shearing through the thick metal as if it were soft lead.

Lounes lifted the chisel. The edge was completely unmarked. It was as sharp,
straight, and true as it had been before the blow. There was no chip, no dent,
and no rounding of the point.

The old blacksmith stared at the tool, his breath coming in short, raspy gasps.
He ran his calloused thumb over the perfect, cold edge of the steel.

"This is not iron, Sidi Amine," Lounes whispered, his eyes wide with a quiet,
terrified awe. "This is... this is a sword of the angels. There is no metal like
this in all of Africa."

"There is now, Lounes," Amine said, his voice quiet, his mind already projecting
the next stage of the drawing-board. "And we are going to use it to build the
rifles."