"I’m not exactly an expert on the subject, though," Jin admitted.
In reality, there were about three types of desiccants commonly used back on Earth.
Silica gel, calcium chloride, and quicklime. While charcoal also possessed moisture-absorbing properties, Jin had decided not to include it as a candidate this time.
Silica gel was silicon dioxide—SiO2—but since the silicon dioxide usually found in nature took the form of quartz or crystal, Jin didn't know how to process it into a moisture-absorbent form. He decided to pass on it.
Calcium chloride was a component of the "nigari" found in seawater, meaning Jin could isolate it. It worked through a phenomenon called deliquescence, where it dissolved into a liquid as it absorbed moisture from the air.
Quicklime was calcium oxide, and Jin knew it could be produced by burning seashells.
Looking at the options, the easiest ones to produce would be calcium chloride and quicklime. However, each had its drawbacks.
While calcium chloride had a high absorption capacity, it eventually turned into an aqueous solution, making it difficult to handle. You couldn't just leave a lump of it lying around.
Then there was quicklime. By absorbing moisture, it became calcium hydroxide—slaked lime—which was useful for neutralizing acidic soil. However, if water was poured directly onto quicklime, it produced a rapid exothermic reaction intense enough to start a fire. There had even been cases where rain leaking onto a bag of quicklime had caused a house fire.
Incidentally, self-heating canned sake used this exact heat-generating property.
"...And that's the gist of it," Jin explained.
He was laying out his desiccant proposals to Elsa, Saki, and Toa.
"Hmm, everything has its pros and cons," Toa remarked, sounding impressed.
"So, the silica gel is too difficult even for you, Jin? In that case, it's a choice between quicklime and calcium chloride. If it were me, I’d choose quicklime," Saki said.
Saki seemed to be favoring the quicklime.
"I think quicklime is better, too," Elsa added. "It’s safe as long as you don't pour water directly on it. If you spilled calcium chloride, it seems like it would be dangerous."
Elsa’s opinion was quite sensible. In fact, on modern Earth, calcium chloride-based desiccants were primarily used for industrial purposes.
"I agree with the quicklime as well," Toa concurred.
"All right, let's go with that then."
Since Hourai Island was an island, it had an abundance of seafood. They harvested many shellfish similar to clams; Jin was actually looking forward to having them in miso soup once they began mass-producing miso.
They were also a staple for stews, so a considerable number of shells had accumulated. As a Magi Craft Meister, Jin never let potential materials go to waste.
"First, an experiment."
When calcium carbonate (CaCO3)—found in shells and limestone—is heated to around 1100 degrees Celsius, carbon dioxide (CO2) is separated, leaving behind calcium oxide (CaO). It was a basic experiment often performed in high school chemistry.
Jin placed the shells into a crucible made of carbon and heated them using the Craft Magic "Heat." Before long, the shells transformed into quicklime.
"Hmm, hmm. This is fascinating."
Toa, the alchemist, watched with intense curiosity.
"Jin's Craft Magic is so convenient. I wish I could use it too," Saki said, peering into the crucible over Jin's shoulder. Her hair brushed past the tip of his nose.
With Ar taking care of her and the daily hot springs on Hourai Island, Saki's hair had become silky smooth, incomparable to how it had been before. Catching the scent of her hair, Jin felt a rare, unexpected flutter in his heart.
"...Jin-nii, does this really generate heat if you pour water on it?"
Elsa, keenly sensing that Jin's face had turned slightly red, peered in from the side opposite Saki, half-forcibly pulling Jin's attention back toward her.
"Ah, yeah. Let's move this to a dish and try it out."
The resulting quicklime reacted with the water, turning into slaked lime as it released a plume of steam.
"Heh, interesting. So this is what you call chemistry."
While Saki was purely enjoying the change, Elsa felt a vague sense of restlessness in her chest. As for Jin, caught between the two of them, he was wondering why his heart was beating faster than usual.
"Well, Jin-kun, the process itself is simple. That means we just need two things: cheap materials and a cheap heating method," Toa summarized.
If they were going to produce this outside of Hourai Island, those were naturally the points they had to consider.
"I'm sure limestone would work just as well as shells, but as for the heat... hmm, firewood probably won't reach 1100 degrees..."
Without using coke and a method to pump in oxygen, it was difficult to achieve a temperature of 1100 degrees Celsius.
"I suppose we'll have to use a magic tool for that part..."
"It’s not for individual use, so if it's managed well, it should be profitable, right?" Toa suggested.
Toa was skilled at calculating cost-performance, perhaps due to his experience. If only he didn't give in to his own material desires so easily... Saki thought privately of her father.
"You're right, Toa-san....I'll make the heater a black box so that it self-destructs if anyone tries to take it apart..."
It seemed Jin already had a plan forming in his head.
"The only question left is where to get that limestone," Saki added.
"Yeah. But for starters, I think using seashells or eggshells would be fine."
As he answered, Jin realized he couldn't set up this plant in the landlocked Klein Kingdom.
"Hmm... shells... shellfish..."
As Jin pondered, he suddenly remembered something.
"Elsa, I recall hearing that fossils of shells were found at Lake Tosmo."
He remembered Berche’s brother, Mattheus, mentioning something like that in Toscosia, the border town between the Celuroa Kingdom and the Shouro Empire.
"Un. There is definitely a place where they can be found....Ah, is there limestone there?"
Jin nodded.
"Yeah. Finding fossils means that place was the bottom of the sea a long time ago. Which means there's a high probability that limestone can be mined there."
Limestone was formed from the accumulation of sea lilies, coral, and shellfish in ancient seas. Therefore, the presence of fossils meant there was a high likelihood of limestone deposits.
"Come to think of it, I haven't been to the Shouro Empire lately..."
Then another thought occurred to him.
"I need to let Barrow and Belle visit home. And I have to report on the demon race situation, too."
That settled it.
"All right, let's head to the Shouro Empire....Though, if we go, it'll have to be three days from now."
"...Why that day?" Saki asked.
"Because Jin-nii's treatment finishes the day after tomorrow," Elsa answered for him.
"Would you and Toa-san like to come along, Saki?"
Toa was the one who answered Jin's invitation.
"No, we go back to our family home quite often. We'll pass this time."
"I see."
Jin then turned to Elsa and asked her the same thing.
"I'm going with you."
Grabbing the hem of Jin's clothes tightly, Elsa answered without a moment's hesitation.
"All right. Then I'll have to talk to those two and get preparations ready. First, I'll go to Reinhard's place to say hello... Oh, that's right, I'll let Reinhard handle this plant project as well."
As she listened to Jin's mutterings, Elsa thought it looked like Adberg's hardships were about to increase once again.
That day, it was also raining in Kaina Village.
Having moved to Nidou, Jin called for Barrow and Belle.
"Eh? A home visit?" the two cried out in unison.
"Is it really okay for us to go back?"
"Yeah, of course. If anything, I feel bad that it's taken this long."
But both Barrow and Belle were too excited to care. It was unclear if they were even listening to Jin's words anymore.
"I've been wanting to visit! Oh, not that I dislike it here. In fact, I want to work here forever!"
"I-I see. That's good then. Er, we'll be heading there via the Kingdom of Egerea. I want you to enjoy the journey."
"Thank you very much!"
In truth, Jin had recently learned from a report by Regulus 5—the Quinta stationed in Blue Land—that Count Kuzuma and Beena were soon to be married, and he wanted to celebrate the occasion. Jin added that detail to the two of them.
"We understand. When that time comes, we shall serve as their butler and maid."
Jin was impressed by how much they had matured.
"We depart in three days. If you have any luggage or souvenirs you want to bring, get them ready. It doesn't matter how much there is."
"Yes, sir!"
When Jin said "it doesn't matter how much," he meant it literally, but the two of them thought it was just a slightly exaggerated way of speaking born from Jin's kindness.
Not that it changed the outcome. The only one who noticed the literal truth of it was Elsa, who was still holding onto the hem of Jin's clothes.