Improved salt production technique

In order to fully explore all possible uses of lime, Li Zhi spent the next period conducting numerous experiments with Liu An. Under Li Zhi’s deliberate guidance, they not only discovered lime’s drying properties, but also its medicinal and adhesive qualities. Most importantly, Li Zhi seized the opportunity to produce cement.

At this very moment, a small patch of ground in Li Zhi’s courtyard, freshly paved with cement, was hardening. Li Zhi’s excitement was palpable as he awaited the ground’s final setting—once it was ready, another lucrative business opportunity would be his.

Of course, their experiments included plenty of failures, to lend authenticity to the process. Otherwise, his abilities would appear too supernatural. Lately, Li Zhi had indeed been a bit too conspicuous. Many officials at court had begun to discuss his recent actions. Some who had previously aligned themselves with him were now secretly suggesting that Li Zhi posed a threat to the Crown Prince, hoping to alert Emperor Taizong that his favoritism toward Li Zhi was becoming excessive.

Although Li Zhi was unafraid, he had no wish to become enemies with Li Chengqian too soon. That had also been his reason for helping Li Tai previously. The plump prince’s thirst for power was far more evident than his own. If possible, it was best to preserve Li Tai’s standing, letting him take the brunt of any conflicts.

After so much preparation, Li Zhi decided it was finally time to produce refined salt. Taking advantage of another ten-day rest, he led Liu An in a flurry of activity. First, he dissolved some coarse salt into brine, then poured the solution through a filtration apparatus of his own design. At the top was a layer of slaked lime, beneath it a piece of sand cloth; the second layer was wood ash, followed by two more layers of sand cloth.

The brine trickled down through the apparatus and collected in a copper basin below. Then, he and Liu An waited patiently for the cloudy brine to settle.

As they waited, Liu An couldn’t help but ask, “Your Highness, do you really think this will purify the salt?”

Li Zhi didn’t give a definitive answer. He merely shrugged and replied, “We’ll never know unless we try. At the very least, it shouldn’t make things worse.”

By now, Liu An was used to Li Zhi’s peculiar methods. Only a few days before, Li Zhi had stopped a wounded kitten’s bleeding with quicklime. The two chatted idly as they watched the brine.

After more than ten minutes, the water had fully settled. Li Zhi had Liu An carefully pour the brine into another copper basin, then set it over a fire to boil. More than half an hour passed before the brine had evaporated, leaving white crystals at the basin’s bottom. Seeing this, Li Zhi quickly had Liu An remove the basin from the fire. Together, they watched the crystals accumulate as the basin cooled.

Once it was cool, Li Zhi reached out, wanting to taste the salt. Unexpectedly, Liu An stopped him, saying, “Please wait, Your Highness, allow your servant to try it first.” Li Zhi knew the refined salt was harmless, but he was deeply moved by Liu An’s devotion. At this moment, Liu An could not have known whether it was safe, and yet he did not hesitate to put himself forward.

As Li Zhi’s heart swelled with gratitude, Liu An placed a bit of salt on his tongue, his face tense with worry. But the anxiety faded quickly as the pure, briny flavor filled his mouth. He savored it carefully, then turned to Li Zhi, excitement in his voice: “Your Highness, I find this salt even purer than the royal supply!”

Li Zhi’s face relaxed in relief at these words. Feigning nonchalance, he said, “Good thing it worked; otherwise, we’d have to find another way.” He reached for some salt to taste himself, but Liu An stopped him again.

“Your Highness, I think it best to test it further.”

“How?” Li Zhi asked.

Liu An thought for a moment before suggesting, “Shall we use it to make food for the wounded cat?”

Li Zhi chuckled, “Are you turning that cat into our guinea pig?”

Liu An replied sheepishly, “Since Your Highness saved it last time, surely having it taste the salt this time won’t hurt.”

Li Zhi agreed, “Very well, have someone prepare food for the cat.” Then he turned to Liu An and added, “Since lime has so many uses, we can’t let it go to waste, can we?”

Liu An asked, “Do you have a new idea, Your Highness?”

Li Zhi replied, “I want to promote the use of lime, so that more people can benefit from its advantages.”

Liu An frowned thoughtfully, “Your Highness, though lime is versatile, words alone won’t easily convince people. Do you have a plan for its promotion?”

Li Zhi smiled, “That’s simple. We only need to make things for people to see.”

Liu An, still puzzled, asked, “How?”

Li Zhi answered, “We can use it to build a house.”

Liu An’s mind raced through all of lime’s properties, realizing this method would indeed best showcase its uses. He couldn’t help but look at Li Zhi with admiration, “Your Highness, your mind is truly agile. You thought of such a way so easily!”

Li Zhi replied with pride, “My intelligence is not something ordinary people can compare to.”

Liu An nodded in complete agreement, finding nothing exaggerated in Li Zhi’s words. As Li Zhi’s personal attendant, he knew well the prince’s breadth of talent—in reading, medicine, and the study of things, Li Zhi surpassed all expectations. His business acumen was equally impressive. The concept of branding he had introduced was gaining acceptance among merchants, and he had even foreseen the need for laws to protect their rights.

Liu An had learned much from Li Zhi recently, most importantly the practice of recording and summarizing each attempt. This made it easier to remember lessons from failure and quickly find solutions.

As expected, the cat suffered no ill effects from eating the prepared food, confirming the success of their improved salt-making method.

With results in hand, Li Zhi turned to Liu An once more and said, “Let’s move on to the study of sugar…”