The pottery kilns beside the riverport smelled of molten borax and bitter salt ash.
Inside the muffle chambers, eight hundred curved baked-clay tiles were cooling down from their second firing at two thousand degrees Fahrenheit.
Through the quartz check ports, the surfaces of the tiles didn’t look like rough, red terra-cotta anymore.
They gleamed with a spotless, glassy enamel. A deep, semi-clear cobalt blue that mirrored the glow of the charcoal fires with diamond bright glare.
Giles Croft stood on the clean brick floor of the pottery shed, wearing heavy leather aprons and asbestos-woven mittens.
He pulled a newly cooled blue tile from the cooling rack, laying it flat upon an oak test bench.
Beside the bench sat an earthen jar containing packed sulfuric acid, distilled by Mistress Pippa from rusted bog-pyrite nodules.
“The test sample is a low-spreading heat-proof glass glassy glaze,” Giles announced, adjusting his glasses.
“Composition: sixty-five percent quartz dust sand, twenty percent anhydrous borax flux, ten percent sodium carbonate, and five percent cobalt aluminate pigment for visual check. The multiplier of heat swelling is three point three times ten to the minus six per degree Celsius, perfectly matched to the heat-proof grog body.”
The preparation of the glaze slip had needed two days of grueling mill work.
In the grinding shed behind the pottery kilns, two water-powered stone edge-runner mills crushed the raw ingredients under heavy granite wheels.
Toby Karr and four apprentices sifted the white powder through fine bronze wire screens, rejecting any grain that couldn’t pass a two-hundred-mesh standard.
“If there’s a single coarse grain of quartz in the mix,” Toby explained to a young novice, “the glaze will pit during firing.
The Lord Baron wants the powder as fine as cosmetic flour. When it melts, it has to flow into an unbroken glassy sheet with zero pinholes.”
Lady Millicent Croft walked down the aisle of grinding tubs, her tally-book open and her brass nib clicking against the thick parchment.
“Six sacks of refined borax hauled from the southern salt flats,” Millicent noted, glancing over her glasses at Giles. “And three jars of imported cobalt oxide from the eastern trading caravans.
Each glazed tile costs fourpence in materials alone, Giles. That is nearly twenty gold sovereigns to armor a single five-hundred-yard stretch of canal dyke.”
“Twenty sovereigns in baked-clay cladding protects a stone retaining structure valued at eight hundred sovereigns,” Giles replied evenly. “If the Rot-Hydra’s acidic bile dissolves the limestone mortar in the dyke, the entire southern embankment will collapse into the canal cut.
The resulting flood would drown the blast fire foundation and wipe out four weeks of heavy-duty production. A twenty-sovereign insurance premium against an eight-hundred-sovereign loss is sound town budgeting.”
Millicent made a neat notation in her ledger. “Acceptable. Provided the tiles don’t chip when the masons set them with hammers.”
Mistress Pippa the Fermenter leaned over the bench with a glass pipette held in her hand. Her runic heat spindle was tucked into her apron pocket.
“If I drop this burning acid on raw limestone,” Pippa warned, holding the pipette over the tile, “it will boil into a white foam that eats a hole through the table.
If I drop it on oak, it turns the wood to charcoal in ten seconds.”
“Apply three drops to the center of the glazed face,” Giles commanded.
Pippa squeezed the rubber bulb.
Three fat, oily droplets of pure packed acid fell onto the gleaming blue surface.
Every eye in the shed fixed on the glass.
There was no hiss.
There was no bubbling white foam.
There was no acrid smoke.
The packed acid sat upon the cobalt blue enamel like morning dew on a waxed apple leaf.
The droplets remained perfectly ball-shaped, beaded high on the iron-hard surface, entirely unable to wet or bite into the glassy quartz dust lattice.
Duncan Stone-Splitter stepped forward, his eyes wide. He reached out with a thick, calloused finger to touch the edge of the tile. But Giles slapped his hand away with his wooden ruler.
“Don’t touch packed acid with your bare skin, Duncan,” Giles said sharply. “The glaze is fully chemically inert, but your outer skin isn’t.”
Duncan wiped his hand on his trousers, staring at the motionless droplets. “It didn’t even leave a watermark. The rock didn’t even cough!”
“It isn’t rock,” Giles said. “It’s a nonstop glassy network of silicon-oxygen tetrahedra cross-linked with boron oxide.
It has zero air holes. Acid can’t corrode a surface it can’t penetrate. Even hydrofluoric acid would need hours to etch this matrix.”
Mistress Pippa let out a soft, breathy laugh, shaking her head. “It looks like winter ice on a northern lake, Lord Giles.
But fire won’t melt it, and the dragon’s bile can’t stain it. If we clad the dykes in this blue glass, Hesketh’s worms could spit on our walls until midsummer and never loosen a single grain of mortar.”
“That’s exactly the design intent,” Giles said.
* * *
Over the next four days, the pottery battery worked around the clock.
Twelve hundred curved, linked coping tiles were pressed, glazed, and fired in nonstop rotation.
At the southern canal locks, Duncan’s masons laid the gleaming blue tiles along five hundred yards of the main dyke crest, bedding them in an acid-proof mortar formulated from ground granulated blast-fire melted rock waste and sodium stone-glass water-glass.
Sister Teresa of the Pure Cistern walked along the newly glazed dyke coping, her linen skirts swishing against the blue tiles.
She reached down, running her fingers over the glassy, zero-drag surface. Her eyes were bright with admiration.
“Not a crack for the rot to hide in,” Teresa said, nodding in deep test. “No pores for the swamp mildew to take root.
A surface that water can’t wet is a surface that sin can’t corrupt. When the rain falls, the filth will wash straight into the ditch without leaving a single stain.”
“It’s non-porous glassy quartz dust, Teresa,” Giles said.
“It resists bacteria and fungal mycelium because it provides zero organic nutrients and offers no clockwork anchor points for hyphae penetration. Cleanliness is merely the natural result of zero surface roughness.”
“You say quartz dust, Lord Master builder,” Teresa said with a calm smile. “I say the holy armor of the righteous. It amounts to the same thing when the mud washes off.”
The result was an unbroken ribbon of polished cobalt blue capping the grey granite walls, shining like a sapphire castle wall against the dreary brown expanse of the Black Fen.
At the same time, Captain Kenneth Drake brought two hundred heavy tall oak body-shield infantry shields to the pottery yard.
The shields were six feet tall, convex. Then he banded in hoop iron—the standard trench mantlet used by Dun-Krag tunnel diggers.
Borin Bronze-Lung’s apprentices dipped the iron-banded faces of the shields into a liquid slip of the heat-proof glass enamel. He fired them individually in a specialized walk-through fire.
When the shields emerged, their outer surfaces were clad in an armored enamel shell that rang like hardened steel when tapped with an axe.
Kenneth Drake walked down the ranks of his shield-bearers. He ran his hand over the slick, mirror-smooth blue finish of the leading tall body-shield.
“The men are calling them the Sky Shields,” Kenneth said, a fierce grin touching his scarred face.
“They say the Lord Baron took a piece of the summer sky and baked it onto their bucklers so the Rot-Mother’s spit can’t burn them.”
“They’re glass-fused baked-clay composites,” Giles replied, checking the thickness of the glaze on a corner rivet with his hair-width.
“The baked-clay face shatters the striking force of an incoming projectile while providing total chemical immunity against acidic spray. The oak backing absorbs the leftover clockwork shock through elastic bending.”
“Whatever you call it,” Kenneth said, “my lads won’t be dropping their shields when the venom flies.”
Before Kenneth could dismiss the check parade, the ground beneath their boots shuddered.
It wasn’t a distant roar this time.
It was a sharp, nearby heave that lifted the pavers of the river terrace by two inches.
A sound like tearing roots and groaning stone ripped through the earth directly beneath the southern drainage dyke.
Fifty paces out along the canal bank, a section of the newly ballasted tramway track suddenly buckled upward.
The heavy oak ties cracked in half with the sound of pistol shots. The crushed granite ballast erupted in geysers of gray dust as three huge mounds of earth bulged toward the sky.
“Breach!” Rook Red-Mane screamed from the watchtower platform, his tracking vane spinning madly. “Burrowers! They’re tunneling beneath the foundation!”
Out of the heaving dirt erupted three monstrous, armored heads.
They were fifteen feet long, segmented like underground centipedes, clad in dripping black hard shell that glistened with acidic slime.
Where their jaws met, four massive, serrated jaws churned the solid clay and granite boulders like wet gravel.
Their milky, blind eyes twitched in the daylight, and from their breathing spiracles came a high, whistling hiss that sprayed clouds of yellow, choking acid vapor across the levee.
The three beasts had bypassed the ditch, the abatis, and the canal.
They were tunneling directly beneath the concrete dyke foundation, undermining the forty-foot wall from below.
A section of the stone embankment began to tilt, the stonework cracking along the mortar joints as the supporting soil was excavated into the underground tunnels.
“They’re dropping the wall into their holes!” Duncan shouted, raising his sledgehammer in futile rage. “We can’t hit them with catapults! They’re inside the earth!”
Captain Kenneth Drake drew his broadsword. He shouted for the shield wall to form on the levee shoulder.
Giles Croft stood on the trembling track bed, adjusting his glasses as the dust settled over his boots.
He looked at the gaping, six-foot burrow holes churning beneath the foundation, then glanced toward the mobile burning lime powder pumping wagons stationed beside the mortar shed.
A pale amber window flickered in the center of his vision.
“They’re attempting an unpermitted underground digging beneath an engineered retaining structure,” Giles said. His voice flat with was cold, town anger.
He turned toward Master Borin and Sister Teresa.
“Borin, connect the two-inch copper delivery hoses to the screw grout pump. Teresa, charge the mixer with fifty bushels of burning lime powder and thirty bags of granulated melted rock waste.”
Giles pulled his wooden ruler from his pocket. He pointed directly down into the nearest open tunnel.
“We’re not digging them out. We’re pressure-grouting their burrows.”