Gunpowder!

The ultimate goal of this trip was clear.

Gather the three essential ingredients for black powder and finally get gunpowder production underway.

As they traveled, Senku walked everyone through black powder's proportions and the details of making it.

An age-old rule of thumb had been passed down for black powder.

One part saltpeter, two parts sulfur, three parts charcoal.

In practical terms, the most reliable basic ratio was seventy-five percent potassium nitrate, ten percent sulfur, and fifteen percent charcoal.

This was the most practical ratio, suitable for all basic production. But for maximum combustion efficiency and explosive power, there was an even more precise, experimentally optimized formula.

Potassium nitrate: 74.64%, sulfur: 11.85%, charcoal: 13.51%.

Senku pushed aside branches blocking the path as he casually explained the process and the precautions.

The most important part of making black powder was never the mixing, but the preparation.

The saltpeter, sulfur, and charcoal had to be ground separately, as finely as possible. The fineness of the powder directly determined how violently it reacted.

And after grinding each ingredient, the tools had to be cleaned thoroughly. Cross-contamination was absolutely forbidden. Mixed-in impurities could render the powder useless at best, or trigger a premature reaction during grinding at worst, making it extremely dangerous.

After grinding, the ingredients had to be weighed to the exact proportions with a high-precision scale. Eyeballing it was out of the question.

Then they needed to be gently folded together and thoroughly mixed throughout, without forceful friction or impacts.

Proper large-scale production used ball mills running at low speed for extended periods to ensure the powders blended evenly and safely.

Mixing the dry powders was not the end. Around eight percent clean water had to be added, and the powder kneaded into a moist, smooth dough, then pressed through a fine sieve into uniform granules and left in a ventilated place to dry completely.

Granulated black powder burned far more consistently than loose dry powder, delivered a more concentrated burst, and was less likely to absorb moisture and become useless.

Taiju looked utterly lost. Scratching his head, he exclaimed, "Oh my god, making gunpowder takes way too many steps!"

Yuzuriha nodded gently. "It is a military weapon, after all."

Li Xiang, on the other hand, was used to this sort of thing. Making gunpowder by hand and all...

No, that was still seriously abnormal!

But with Senku around, he could even build you a rocket, okay? (He really did.)

"Don't worry," Li Xiang said calmly. "We just need to find all the raw materials. Leave the rest to Senku."

The four trekked over mountains and ridges, following the geological formations toward the volcanic region.

The deep mountain forests were lush and the air was fresh. After they had walked for most of the morning, a warm, humid breeze washed over their faces, carrying a faint scent of sulfur.

Mist curled between the trees ahead, white vapor slowly rising as the ground grew noticeably warmer.

"A natural hot spring!"

Senku's eyes lit up, and he immediately pinpointed their direction.

Volcanic terrain was bound to have geothermal hot springs nearby. Not only did this confirm that sulfur deposits were close, it also gave everyone a chance to stop and rest after traveling all morning.

The nonstop walking had left them lightly coated in sweat, their legs aching.

The four simply stopped, setting aside their gathering mission for the moment to take a short break beside the hot spring.

Warm spring water murmured along amid drifting steam. Warmth seeped through their limbs, dispelling most of their fatigue in an instant.

After the brief rest, the four were fully refreshed and resumed their search for materials.

With the hot spring's sulfurous scent to guide them, finding sulfur ore proved especially easy.

They divided the work clearly.

Taiju easily chipped off large chunks of natural sulfur ore.

Senku selected high-quality ore with few impurities and marked the usable material. Li Xiang handled the initial cleaning, removing dirt and impurities, while Yuzuriha packed the sulfur securely into their storage bags.

With the sulfur collected, saltpeter and charcoal were next.

Naturally formed saltpeter crystals lay hidden on weathered rock faces, inside dry tree hollows, and in layers of decomposed soil. The four split up to search and soon gathered potassium nitrate deposits of sufficient purity.

Charcoal was the easiest. They selected hardwood on the spot and charred it in an enclosed space, keeping the air out. In just half a day, they produced exceptionally pure wood charcoal.

All three essential ingredients had been gathered.

With their gathering mission successfully completed, they did not linger. They changed direction and headed for the coast.

Senku planned to collect some special coastal minerals along the way, which could later improve the gunpowder formula and increase its stability.

They passed through dense forest and crossed sloping ground. The instant the view opened up completely, a salty sea breeze swept over them.

The azure sea stretched to the far edge of the horizon. Wave after wave lapped against the beach, its glittering waters seemingly endless.

The vast ocean view struck them all at once.

"Whoa, whoa, whoa-! It's the ocean!!" Taiju got excited, Taiju took flight, Taiju leaped.

He pushed off the ground and sprang straight into the shallow surf, hopping through the seawater and sending spray flying everywhere.

Boisterous laughter rang across the beach.

Compared with Taiju's wild antics, the other three were much quieter.

A gentle sea breeze brushed across the beach. Small shells, washed clean by the waves, lay scattered over the soft yellow sand in a riot of colors.

Yuzuriha bent down and slowly crouched on the beach, carefully picking up pretty little shells and slipping them into her pockets.

Senku did not join the fun. He kept his head down, examining minerals in the exposed rock layers along the beach and quietly gathering the coastal materials he needed, recording data as he studied the terrain.

Li Xiang strolled along the beach, occasionally bending to pick up an unusually shaped shell.

She filled jars with quite a lot of seawater.

Once they had played to their hearts' content-though it was mostly shell collecting-they settled down and immediately headed back to camp without further delay.

The truly tedious, painstaking production process was only just beginning.

Only after returning to camp did the work officially begin.

First came the meticulous processing of the raw materials.

The three ingredients were processed strictly separately, with cross-contamination prevented throughout.

Taiju took charge of the most physically demanding task: grinding. The natural mineral chunks were extremely hard.

The saltpeter was ground dozens of times, with coarse grains sifted out to leave a fine, snowlike white powder.

The sulfur ore was ground into an even, pale yellow powder.

The charcoal chunks were thoroughly crushed and ground, then filtered to remove impurities, yielding a lightweight, pure black charcoal powder.

After each ingredient was ground, Li Xiang carefully cleaned and wiped down the tools. Only once she confirmed that no residue remained did they move on to the next ingredient.

This step alone took most of the day.

Once all the powders met the required standard, Senku brought out his homemade precision balance and weighed them strictly according to the classic, safe ratio of 75:10:15. Every portion was precisely measured, with not the slightest error allowed.

With the proportions measured out, they moved on to mixing.

Without a modern ball mill, the four used the most reliable manual wet-mixing method.

Senku directed everyone to fold the three powders together gently, keeping their movements slow and even to avoid intense friction.

Once the dry powders were thoroughly blended, they added the measured clean water in small increments, kneading and pressing the loose powder into a moist, dense mass.

The moisture content was strictly maintained at eight percent: neither dry nor runny, with just the right pliability.

After kneading it evenly, they repeatedly pressed it through a fine sieve to form small, uniformly sized round granules, then spread them neatly over clean stone slabs to air-dry in the shade.

The gunpowder could never be left in direct sunlight. It could only dry naturally in the shade, since heat from sun exposure could easily create a dangerous situation.

The first day's work ended with the granules laid out to dry.

Early the next morning, the four got up at daybreak to continue the finishing work.

After an entire night of drying in a ventilated, shaded spot, the granules were dry on the surface, but moisture still remained inside.

They turned them in batches, spread them out in layers to dry, and checked them carefully again and again, ensuring that every granule had lost all its moisture and was completely dry.

Once they were thoroughly dry, Senku lightly ground them again to even them out, fine-tuning their compactness to make the burn rate more consistent.

From gathering raw minerals, purifying them and removing impurities, grinding them separately, precisely measuring the proportions, mixing them dry and wet, shaping the granules, and thoroughly drying them in the shade, to a second round of inspections and refinements.

Two full days and nights of tedious work, day after day, with countless rounds of grinding, sifting, mixing, and drying.

At the moment the final granule dried completely and became stable.

The first batch of handmade black powder in Dr. STONE was officially complete!

Coca-Cola, Coca-Cola.

Looking at the black powder granules neatly arranged on the stone slabs, these things could hardly have been better suited to taking on that inhuman monster, Tsukasa.

[Kids, don't go trying to make this stuff yourselves.]