Rewrite That Witch
CH270 · Rewrite
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Chapter 270: High-Pressure Air Bottle

After the others left, Roland and Barov remained.

“You saw it yourself — the chemical laboratory and Graycastle Industry are both critically short of personnel.” Roland leaned forward. “I’m also planning to start mass-producing soap and perfume soon, which will demand additional staff beyond what either operation currently has. But it will be at least a year before most of the town’s residents pass the primary education examination. And even taking all of them together, we won’t have more than six or seven hundred people. That isn’t enough. I need people from outside.”

“If we recruit from the stronghold —”

“No.” Roland shook his head. “Next year, once Border Town achieves city status, the stronghold and the town merge into a single entity. Moving workers from one to the other is moving money from the left pocket to the right. I need people from outside the Western Territory.”

Barov’s expression shifted to one of careful worry. “That is not so easy to arrange, Your Highness. If we recruit from other cities, the local lords will not sit quietly and watch.”

“Not from the cities.” Roland dipped a finger into the ice water and drew a line across the tabletop. “Have you noticed — since the Months of Demons ended, Graycastle has been in constant conflict. Timothy’s campaigns in the South destroyed Eagle City, damaged the surrounding towns and villages. His subjugation of the North stripped Duke Ise of title and territory. His naval assault on the East hit the Sea Wind Region, Valencia, and Shivering Crow Castle — not to mention every small town caught between them.” He tapped the table twice, leaving a scattering of wet marks. “Look at the people already flooding into King’s City. That shows the scale of the displacement.”

“You mean…” Barov’s expression changed.

“Spread word about the Western Region.” Roland smoothed the water marks with his palm. “For six months, only the West has remained at peace. No forced conscription. No armies burning through the countryside. Timothy uses commoners as battlefield material — who can guarantee that the next campaign won’t take their village? Make that contrast explicit. Propagandize that the only place in Graycastle completely untouched by war is here.”

“I think I understand,” Barov said slowly, choosing his words. “You want to attract displaced civilians by offering them something no one else is offering: no military service, no forced labor, a place to live, food to eat, stable work.”

“Almost exactly.” Roland nodded. There it was — the ability to cut to the essential point, which was one of Barov’s genuine strengths. “But one particular emphasis: make clear what literate people can expect here. The treatment for those who can read and write, or who have technical skills. Because there are certainly knights and minor nobles out there with nowhere to turn — people who can’t protect their territories in the current chaos, who need somewhere to wait out the war. Those people are exactly who I want.”

The logic held in both directions. During peacetime, even a small, barren territory gave a minor lord enough to eat and a reason to stay. But wartime disrupted that equation completely. If there was a stable destination that offered real wages and an eventual return, the temptation to relocate — temporarily, with the intention of going back — would be substantial. And if they came to the Western Region first, many would not leave.

As for how to run the actual recruitment campaign, Barov would find his methods. That much Roland trusted.

“There is one difficulty,” Barov said carefully. “Settling new arrivals costs money. And we cannot interrupt the grain acquisition. If Margaret’s caravan encounters any mishap along the way, the treasury will run dry before the end of the month.”

“That’s a fair concern.” Roland touched his chin. The most important task of a new political power is to build trust. A missed payroll, a failed promise — that kind of crack doesn’t heal quickly. “In that case, hold off on implementation. Wait until the caravan arrives and the steam engine sale is complete. Once the treasury recovers, we’ll speak about it again.”

“As you bid, Your Royal Highness.” Barov pressed his hand to his chest.

Back in his office, Roland turned his attention to the matter that had been sitting at the back of his mind through the entire meeting: Margaret’s balloon order.

One thousand gold royals per balloon — priced above even the steam engine, though the production cost was substantially lower. The airbag was essentially a large painted canvas, Soraya’s coating magic sealing it against heat and puncture; the hemp rope and bamboo basket were near-trivial. He had already built and tested a prototype in the factory courtyard: a hydrogen balloon capable of carrying both Lightning and Maggie simultaneously and ascending cleanly into the sky.

He had ruled out the hot air balloon approach long ago. The coal-gas equipment took up too much space, the manufacturing process was cumbersome, and importing coal from other cities made small-scale production absurdly uneconomical. Hydrogen was simpler. The prototype’s airbag, coated single-sided, weighed almost nothing — flexible, resistant to rain, impact, and fire alike. Even Maggie’s transformation attacks in various bird forms had failed to leave a mark. Only an iron needle could puncture the millimeter-thick coating. A two-meter diameter hydrogen balloon was already sufficient to lift an adult.

The unsolved problem was the high-pressure hydrogen bottle.

A DC motor for electrolysis was out of the question — selling the technology was not viable, and a motor driving a steam engine to produce hydrogen was cost-ineffective for regular refills. If he wanted a steady revenue stream from wealthy merchants, he needed a portable, refillable high-pressure bottle.

The bottle itself presented no real obstacle. Pig iron and wrought iron, with walls thick enough to compensate for material variance, and Anna’s precision in manufacture — the bottle could be built. The difficulty was pressure. Bottles from Roland’s world operated at twenty megapascals or higher. Reaching even a fraction of that with a bicycle pump was fantasy. Ten Qilins pedaling in shifts wouldn’t close the gap. He needed a high-pressure pump.

High-pressure air pumps came in two forms: piston compressors and turbine compressors. The piston type belonged to the internal combustion engine technology tree; the turbine type to turbine engines. Either development path was time-consuming and expensive beyond what the current project justified.

By late afternoon, sitting in the yellow slant of sun through the office window, Roland arrived at a different solution entirely.

The idea came from a news item lodged somewhere in his memory: a street vendor had been filling hydrogen balloons using a modified liquefied gas tank, storing the hydrogen by reacting diluted sulfuric acid with aluminum inside the vessel. The pressure had built beyond what the tank could hold, and it had exploded. The lesson was clear: the self-pressurizing approach worked — if the reaction quantities were correctly calculated.

The self-inflating bottle, then. Pour diluted sulfuric acid and an active metal directly into the bottle. The chemical reaction generates hydrogen, which has nowhere to escape — pressure builds inside the sealed vessel. When the valve is opened, the hydrogen pours directly into the airbag. The refill process was equally simple: remove the gas nozzle, heat the bottle to drive off the remaining liquid, clear out the ferrous sulfate crystals, and refill with fresh reactant.

Zinc and aluminum were the standard metals for this reaction in laboratory settings, but neither was easily available in this era. Roland’s solution: Lucia’s power to decompose and purify iron, combined with heat treatment and surface-area increase — thin iron strips or iron powder — to compensate for iron’s slower reaction rate at room temperature. An inner coating would protect the bottle walls against acid corrosion.

He sketched the design on paper. To minimize gas leakage, the bottle needed to be formed as a single piece with only one opening — a threaded hole at the top, into which a valve with a gas nozzle could be screwed. Tighten the mouthpiece after loading the reactants; the hydrogen accumulates; pressure climbs. Unscrew the valve when ready to fill the balloon.

Diluted sulfuric acid was itself an alchemy product — not cheap. The refill price would reflect that.

Fifty gold royals per charge, Roland decided. Buy ten, get one free.

He set down the sketch and looked at it in the fading afternoon light. The design was simple enough. The engineering was manageable. And if it worked — if Lucia’s purified iron reacted cleanly enough with the diluted acid to fill a balloon under reliable pressure — then the Redwater Bridge and the harvest and the plenary session and all the rest of it would not be the ceiling of what Border Town could build.

They were the floor.

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