"I guess a refrigerator is out of the question for now..."
Jin gave up on the idea. He had spent some time brainstorming ways to build a refrigerator for food preservation, but he was overwhelmingly short on materials. At the very least, he needed a water-attribute magi-stone.
"There's a volcano nearby, so it makes sense that we'd find fire-attribute magi-stones. By that same logic, finding water-attribute ones here is probably impossible."
Apparently, water-attribute magi-stones were rare in the natural world to begin with.
"Maybe I could make one if I went to the royal capital..."
With the refrigerator project shelved for the time being, Jin turned his attention to something else: transportation.
Jin planned to eventually sell the manufacturing method for his stoves to Roland. When that happened, he wanted to make the fire-attribute magi-stones gathered from the Erme River a local specialty, turning them into a steady source of income for the village.
However, transporting them would become a problem when Roland carried the goods by carriage. If the shipping costs were too high, there was a risk that customers would simply buy fire-attribute magi-stones from other sources. Consequently, improving the efficiency of transport was essential.
There's quite an altitude difference between here and the royal capital, he thought.
Based on what he had gathered from conversations, Kaina Village sat at an elevation of approximately 1,000 meters. That was why this village, despite being located in the south, remained relatively comfortable even in the height of summer.
The way back is fine since it's all downhill, but the trip up here must be a nightmare.
Since the return trip with the cargo was downhill, it was manageable. However, the uphill journey to the village was so difficult that it likely limited merchant visits to once every two months.
"Man, I'd love to develop a motor or an engine."
It might be possible back at his predecessor’s laboratory, but here, it was out of the question. In that case...
"It'll have to be improvements to the carriages," Jin concluded. He began to identify specific points for an overhaul.
"To make it easier for the horses to pull, ball bearings are a must."
He focused on what he could realistically achieve with his current resources.
"And I really want to swap those wheels for rubber tires. That means I need to find a tree that produces natural rubber."
Back when he had worked part-time at a camera shop, he had heard a story about a resin called gutta-percha. It wasn't the standard rubber from a rubber tree, but a resin from a different species that a famous German camera manufacturer used for its camera body coverings.
That tree was found in places like China, and its bark could be brewed into a medicinal tea.
"The tea they drink in this village... I wonder if those trees produce white sap."
He decided to investigate. When it came to local flora, Hanna was the person to ask.
"Hanna, let's go gather some tea leaves."
When Jin called out to her, she answered immediately.
"Okay!"
Carrying a small basket, they headed into the forest.
"There it is! It's this tree."
Hanna pointed out the tree the villagers simply called the "tea tree."
"Alright, let's pick some of the young leaves."
"Yup!"
The trees grew in abundance in one corner of the forest. When Jin tore a leaf, it pulled away with sticky, elastic threads. This was definitely the raw material for rubber.
Having memorized the tree's characteristics, Jin returned home to drop off the leaves and then headed back into the forest alone.
"I don't want to kill the trees by over-harvesting, though."
To avoid environmental damage, he made small incisions in various trees and tied shallow dishes to the trunks to collect the oozing sap.
"Alright. If I wait until tomorrow, I should have a decent amount."
He was imitating the rubber-tapping techniques he’d seen once on TV.
While waiting for the sap to accumulate, he went back to work on the bearings.
"Onii-chan, what are you making now?"
Lately, Hanna had taken to watching Jin work, finding his magical crafting fascinating.
"Just watch... Forming."
"Whoa, that’s so cool!"
The lump of iron morphed into perfect spheres right before her eyes. Furthermore, there were dozens of them, all identical in size down to the micron. This was the kind of precision processing that only a Magi Craft Meister could perform.
"Carburizing."
This was one of Jin's original spells, designed to infuse iron with carbon. Through this process, ordinary iron was transformed into tough steel.
He created the outer rings, inner rings, and ball retainers in the same manner. Once he assembled the pieces, the ball bearing was complete. Since he had finished the process with a Hardening spell, their durability was guaranteed.
"What is it?"
The finished product meant little to Hanna. Looking somewhat bored, she wandered off to help with dinner preparations.
Jin gave a wry smile and prepared axles and wheels of the appropriate thickness to fit the bearings. He finished the day by modifying the handcart Hanna used for carrying water, equipping it with the new bearings.
The next morning, when Hanna returned from drawing water, she looked puzzled.
"Onii-chan, did you do something to my handcart?"
"Remember that thing I was making yesterday? I attached it to the wheels," Jin explained.
"It moves so lightly now! I thought I’d suddenly gotten really strong, but it was just you, Onii-chan!"
She looked at Jin with a face that was caught between being impressed and slightly disappointed that her "super strength" wasn't real.
"Now then, let's check on that natural rubber."
After breakfast, Jin went into the forest to check the sap collection.
"Oh, the dishes are practically full."
The sap had filled most of the dishes he’d set out. He transferred the liquid into a bucket he’d brought along and left the dishes to continue collecting.
"Right, next is vulcanization."
In its raw state, natural rubber is soft and prone to melting when heated, making it difficult to use. By mixing in a small percentage of sulfur, it gains a more useful level of hardness.
"I've only read about it, though. I've never actually done it myself."
Sulfur was abundant near Death Mountain, and Jin had gathered some during his spare time, thinking it might be useful eventually.
"Time for some trial and error."
He started by mixing in about five percent sulfur. The result was too soft. He tried ten percent. Still a bit soft. Fifteen percent felt just right. Twenty percent was quite hard. At thirty percent, it wasn't really rubber anymore; Jin suspected this was what people called ebonite.
"Now, what should I make with this prototype rubber?"
Normally, vulcanized rubber cannot be melted down and reshaped. The standard procedure is to shape the item before the sulfur is added, but Jin’s magic bypassed those limitations.
"Alright. Forming."
He used the prototype rubber to create balls. They were hollow, of course. He made a large one the size of a dodgeball, medium ones like handballs, and small ones like baseballs. He also fashioned several inner tubes.
"The kids will love these."
He went to look for Hanna. Lately, her shyness had completely vanished, and she spent much of her time playing with the other village children. Jin checked the village square, but it was empty due to the midday heat.
"They must be at the river."
When he arrived at the Erme River, he found the children swimming, just as he’d thought. Hanna was there, too. Spotting Jin, she climbed out of the water and ran over.
"Onii-chan, what's that?" she asked, eyeing the tubes and balls.
"This is a ball. And these are inner tubes."
"What do you do with them?"
"What's that thing?"
"Jin-nii, what did you make this time?"
"Jin-san, what are these?"
It wasn't just the children; Barbara, who had likely been gathering fire magi-stones in the river, walked over as well.
"With this ball, you can play by throwing and catching it like this."
Jin tossed the dodgeball to Kurt. The mischievous boy was caught off guard but managed a skillful catch.
"Nice catch. Now try throwing it to someone else."
"Alright! Mario, catch!"
"Whoa, wait—! Hey, it's really light!"
Because it was hollow, it was much lighter than its size suggested. The boys immediately started playing catch. Jin handed the smaller handballs to the girls.
"These are handballs. You can throw them, but you can also bounce them like this."
Finding a patch of flat ground, Jin demonstrated how to bounce the ball.
"Oh, let me try! Let me try!"
The energetic Jessie jumped in immediately. She accidentally sent the ball flying into the distance a few times as she adjusted to the bounce, but she improved quickly.
Finally, Jin brought out the two inner tubes he had been carrying over his arms.
"These are called inner tubes. You get inside the ring and hold onto it with your arms. Now, try getting in the water."
He gave them to Jim and Patty, two of the younger children who couldn't swim yet and usually stayed in the shallows. When they stepped into the water:
"Whoa, I'm floating!"
They were absolutely delighted.
Seeing how much fun they were having, Barbara looked on with an envious expression. Jin recalled that she always stayed in the shallow areas as well.
"Barbara-san, can you not swim?"
When he asked, her face turned bright red. Jin decided right then that he would make another tube for her later.