Li Ying frowned.
She carefully examined the large barrels of tung oil stacked in the corner and said in a low voice, "Have you ever thought, Lord Lu, that although tung oil can prevent water, when the ship is sailing, the bottom of the ship is soaked in the sea all day long without seeing sunlight. At that time, many barnacles and mussels will surely attach to it."
These marine creatures cling tightly to the hull. Over the years, firstly, they increase the ship's own weight and reduce its buoyancy. Secondly, they will corrode the hull, greatly increasing the risk of navigation.
Even the ten - thousand - ton steel ships in later generations can't escape the erosion of these inconspicuous small creatures, let alone Lord Lu Xunguang's dragon boat, which is only made of camphor wood.
Lu Xunguang frowned tightly. How could he not know this truth?
When disassembling the bottom of the old dragon boat, they found many white, worm - like things in the rotten and damp wooden boards.
The shipbuilders were at a loss. They called these things shipworms. They like to bore holes in wooden ships and can often bite through the ship's planks. They also reproduce very quickly. They can lay a nest of tiny eggs that are hardly noticeable in just over a month. By the time the shipbuilders notice, the hull is often damaged beyond repair.
Lu Xunguang also asked the experienced shipbuilders. If they wanted to prevent the shipworms, the only way was to regularly dock the ship in freshwater rivers and lakes. Once the shipworms left the sea, they would naturally not live long.
When the emperor made his southern tour, all the routes were on the sea. How could there be a chance to dock in a port?
Helpless, he could only arrange several strong and good - swimmers to dive into the sea every day to check the bottom of the ship. If they found shipworms, they would remove them in time and make repairs.
Li Ying shook her head repeatedly seeing his helpless look.
"Lord Lu, I have a way to solve the problem of shipworms."
Just then, the Minister of the Ministry of Revenue returned. Hearing Li Ying's words, his eyes also lit up.
"Miss Li, are you serious?"
Li Ying slowly walked two steps towards the direction where the tung oil was stacked and said softly, "Lord Lu, have you ever heard of 'Xiuyou oil'?"
Seeing that both of them looked puzzled, Li Ying didn't keep them in suspense and directly explained, "This Xiuyou oil is somewhat related to tung oil, but it is slightly poisonous. If it is used to paint the bottom of the ship, most of the shipworms and mussels attached to the planks will die of poisoning and won't be able to damage the hull."
The Minister of the Ministry of Revenue was overjoyed and hurriedly asked, "Is there really such a miraculous thing in the world? Miss Li, quickly tell us how to obtain this 'Xiuyou oil'?"
Just as Li Ying was about to speak, Lu Xunguang quietly pulled her behind him and blocked her tightly.
"Your Excellency, we are ordered to repair the dragon boat. Thanks to A Ying's extensive reading, she mentioned this 'Xiuyou oil' which can solve our urgent problem. We should go and search for it ourselves. If we rely on A Ying for everything, it will be a laughingstock if it gets out that a dignified minister always asks a girl who is not related to him for solutions."
The Minister of the Ministry of Revenue blushed. Then he quickly came to his senses. Lu Xunguang was obviously deliberately making things difficult for him. It was clearly because he had just joked that Li Ying was just an unimportant "beauty companion", and Lu Xunguang was unhappy and wanted to vent his anger for Li Ying.
But this matter was crucial, so he didn't dare to be negligent anymore. He said with a smiling face, "Miss Li, I was really blind and short - sighted. Please teach me without reservation."
Li Ying found Lu Xunguang's serious look funny.
What a petty - minded Lord Lu.
But she liked it.
Li Ying decided to stop while she was ahead. She smiled and gracefully curtsied to the Minister of the Ministry of Revenue.
"Your Excellency, what are you saying! I've just read a few miscellaneous books in my spare time. If I can help you two share your worries, I will surely tell you everything I know."
"To make this Xiuyou oil, besides 60% tung oil, we also need 40% secondary tung oil and soot. Your Excellency, don't be impatient. Listen to me carefully."
The so - called "secondary tung oil" is the oil residue obtained by heating and filtering the extracted tung oil. Soot is made by stir - frying tung cake powder.
Grind the tung seeds into fine powder. Heat an iron pan with coal fire and keep stir - frying the tung cake powder. Then add the tung oil residue. The high temperature makes the black tar in the tung oil firmly attach to the dry cake powder. After it cools down, it becomes soot.
This soot is as black as ink, faintly shining with an oily sheen, but it is not sticky.
Only the Xiuyou oil with soot added will not easily gel locally and produce glue beads during high - temperature boiling, thus maintaining the thickness of the paint.
Moreover, this soot can also dye the tung oil a reddish - brown color and extend the preservation period of the Xiuyou oil. After the color of the soot is completely dissolved, the remaining soot residue can be fished out from the Xiuyou oil. The secondary tung oil obtained by re - squeezing can be recycled and become the raw material for Xiuyou oil again.
The Xiuyou oil made in this way only adds a few more processes, but it has a clear color like amber, is thick and viscous, has extremely strong adhesion, forms an extremely tough oil film, and dries very quickly.
After the hull is painted with tung oil to prevent water seepage, and then painted with Xiuyou oil, it will be moisture - proof, anti - corrosive, anti - rust, acid - and alkali - resistant, and can also prevent snails, mussels from adsorbing on the bottom of the ship and moss from growing, reducing the resistance during navigation.
Li Ying explained everything in detail. Lu Xunguang, who had long known she had many good ideas, was not surprised. But the Minister of the Ministry of Revenue stared at her with a skeptical look.
"Miss Li, is this 'Xiuyou oil' you mentioned really that miraculous?"
Although he was skeptical, it only meant that his subordinates had to do two more processes, which was not a big deal.
The Minister of the Ministry of Revenue excitedly took the prescription written by Li Ying and went to find the craftsmen to refine the Xiuyou oil.
Li Ying watched him leave, but her eyes fell on the mountain of debris from the bottom of the ship piled in the corner.
Several craftsmen were about to carry all these wastes away to discard them. Li Ying quickly shouted, "Lord Lu, wait!"
Although Lu Xunguang was puzzled, he still followed her words and told the craftsmen to put down the bamboo baskets.
Li Ying excitedly ran forward, bent down, and began to pick and choose.
"These oysters are quite fat. They are just right for roasting with golden garlic. The whelks can be stir - fried spicy. They can be a snack to pass the time. And these barnacles..."
She was overjoyed and counted them one by one as if they were treasures. But Lu Xunguang couldn't help frowning secretly.
"A Ying, if you want to eat, just ask the servants to buy them. Why bother rummaging through these wastes?"
Li Ying waved her hand indifferently.
These mussels and oysters had been growing safely under the dragon boat for many years. Each one had extremely fat and tender meat. Moreover, the barnacles were as big as a child's fist, which was really rare. As a gourmet, how could she let go of this delicious food that came to her?
"Lord Lu, these barnacles are rare things. Their taste far surpasses that of any fish, shrimp, or shellfish!"
Lu Xunguang looked at the strange stone - like things in her hand and couldn't help frowning.
When the craftsmen removed these things, he saw with his own eyes that they had to use a lot of effort to chisel them off. How could one eat such rock - hard things!