Summer was ending as the first signs of autumn appeared on the valley, leaves fell, mushrooms grew after a rainy day, days got shorter and the nights got colder as the wild animals hunted more to prepare for winter. He'd been pondering a new project, one that would revolutionize their way of life. It was time to introduce a new material to their tribe: concrete.
His clay and wood wall at the entrance of the caves had worked so far, but he wanted something more permanent.
Shak'Ar: 'I can do this,' he thought. 'They'll understand once they see it.'
Shak'Ar: "Anzu," Shak'Ar said, turning to her "I've been thinking about something that will change how we live, something that will warm our bodies and keep us healthy."
Anzu raised an eyebrow, intrigued: "What is it this time, Shak'Ar?"
Shak'Ar: "A bath," he said with a grin. "Not just the cold river. A warm, soothing bath made of stone and heated by fire."
Anzu: "A bath?" Anzu tilted her head, trying to picture it. "Like the river, but... warmer? How would that even work?"
Shak'Ar: "Trust me," he said, his eyes gleaming excitedly. "We'll need limestone, ash, and water. Together, they'll create something stronger than stone, I call it concrete."
Anzu frowned: "Concrete? What's that?"
Shak'Ar: "It's a mixture," Shak'Ar explained. "The ash and water react with the lime of the fired limestone, forming a material that hardens over time. It's durable and can hold water."
Anzu gave him a doubtful look but sighed, this wasn't the first time he had come up with something strange, just his harpoons had started to become popular, and growing edible plants seemed like a really good idea.
Anzu stood up: "Alright, let's go, I will help you" She really wanted to see what he would make this time.
Shak'Ar: "Great, I will go get the rocks, collect wood for me in the meantime, and also black sand and clay by the river"
Anzu nodded and went to prepare.
Shak'Ar led a small group to the mountains to gather materials, including his father, Othar, and uncle, Vit'a.
The journey took a while, but Othar and Vit'a knew the area well, so they found the rocks he needed after some hours of searching.
Othar watched as Shak'Ar examined a large, gray rock. "This limestone will be perfect," Shak'Ar declared.
Othar: "Why do we need this rock?" Othar grunted. "The river's always been enough for bathing."
Shak'Ar: "Father," Shak'Ar said patiently, "This is different. Mixing this limestone with ash and water will create a paste that hardens like stone. It'll form walls that can hold water... and of course, it will be fireproof so we can even heat the water!"
Othar shook his head: "And where will this water come from? Are you going to drag the river to the cave?"
Shak'Ar smirked: "The tribe can help us for now. Later, I'll build a concrete pond outside to collect it from the rain."
Back at the cave, Shak'Ar began the process. He crushed the limestone into powder, explaining as he worked. "When we heat limestone, it releases a gas—carbon dioxide—and turns into quicklime. We then mix it with water, turning it into a paste called slaked lime. Combined with volcanic sand from the riverside and wood ash, it will harden into concrete! "
The tribesmen watched, skeptical but curious. Shak'Ar built a fire pit, placing chunks of limestone over it. As the stones glowed red-hot, they began to crack and crumble, turning into quicklime. Carefully, he picked them up using two sticks and poured them inside a clay pot with water, and it instantly dissolved bubbling violently.
Anzu: "It's fizzing!" Anzu exclaimed, watching the bubbling reaction. Everyone else was also surprised as they took a step back.
Shak'Ar nodded. "That's the heat from the reaction. It's turning into slaked lime. Now, we add the sand and some wood ash."
He combined the slaked lime with volcanic sand, ashes, and water, creating a thick, gray paste. "This will harden over time, becoming even stronger than it looks now." he then made sample bricks with different mixtures for testing.
It took him some time, but he finally got a concrete mix that had the consistency and strength he wanted.
Using that concrete mix, Shak'Ar constructed the bath. First, he formed bricks and cylinders from the mixture, leaving them in the sun to dry. Once hardened, he lined a basin with the bricks and coated the walls with fresh concrete. Leaving a space underneath for the hot air to circulate from the furnace chimney to the left.
Anzu watched him work, marveling at his precision. "This is going to be amazing," she said. She really liked Shak'Ar's face of concentration when he worked on projects.
"The best part is yet to come," Shak'Ar replied, smearing the final layer of concrete onto the walls to smooth it out.
The heating system was the most challenging innovation. Shak'Ar crafted a curved chimney from fired clay cylinders, channeling smoke from a furnace beside the bath but not touching it, to avoid the heat cracking the concrete. Taking inspiration from Roman therms ruins he had seen in Spain.
"This will keep the bath warm without filling the cave with smoke," he explained to Othar, who had reluctantly helped shape the clay.
Othar grunted: "You've got a clever mind, boy. Let's hope it works."
It took a lot of effort and they had to wait a couple of days for it to harden, as they kept the concrete moist and applied new smooth layers to make sure it would hold water, and wouldn't crack with the heat, he even lined the bottom with small smooth stones from the river.
When the bath was complete, the tribe gathered to admire Shak'Ar's creation. The smooth gray surface of the concrete contrasted sharply with the rugged cave walls.
Jhana: "It's beautiful," said Jhana, Shak'Ar's mother, her voice filled with pride as she caressed the smooth concrete, polished layer after layer.
Anzu: "Let's try it!" Anzu exclaimed, eager to test the warm bath.
Shak'Ar filled the bath with water and lit the fire. Soon enough, steam rose, and the water grew comfortably warm. He, Anzu, and a few family members stepped in, their bodies relaxing as the warmth seeped into their muscles. They had to take turns as the bath wasn't that big.
Anzu: "This is incredible," Anzu said, leaning back against the smooth wall.
Shak'Ar: 'That was worth every moment,' Shak'Ar thought, watching the smiles on their faces, as other tribespeople also started to take turns getting into the bath, they had to even change the water two times from the grime that accumulated.
Rahiki, the tribe's shaman, emerged from the bath with a broad grin: "I feel rejuvenated. This will be a gift to the tribe, Shak'Ar."
As the days passed, Shak'Ar's mind turned to other ideas to improve the lives, and health of his tribe. He remembered something else from his past life: soap.
'Fats and lye,' he thought, recalling the basic recipe. 'But where do I get lye here?'
He experimented with wood ash, mixing it with water to create an alkaline solution rich in potassium hydroxide. He produced a crude paste by combining this with heated and rendered animal fat. The first results were inconsistent, but Rahiki suggested adding herbs and minerals to enhance the mixture, and trying different ashes mixures, and finally saponification happened with a consistency he was happy with. He made soap bars full of dried medicinal herbs by adding them to the mixture and letting it cool down on clay molds he had fired previously.
With time, Shak'Ar developed a rudimentary soap, bringing yet another innovation to his tribe.
Shak'Ar: 'One step at a time,' he thought, watching his people adapt to the changes. 'We'll make this world ours.'