59: Chapter 59 Principles of Alkali Cooking for Papermaking

The raw material used for Xishan Jade Paper is Tender Moso Bamboo.

It fully inherits the papermaking techniques of Cai Lun and is a traditional handicraft with a long history.

It is sourced from high-quality raw materials from Longqi Mountain—Tender Moso Bamboo—which is why Xishan Paper is also known as "Bamboo Paper."

Its texture is fine, delicate yet resilient, and white as snow; writing on it is clear, it has strong water absorption, stable color, and does not rot even when stored for a long time.

It enjoys the reputation of "Paper that lasts a hundred years, pure as jade and clear as ice."

It can be used for restoring and printing old books, as well as for calligraphy and mounting, possessing a very classic and elegant charm.

Zhao Fusu looked at the detailed steps for making Xishan Jade Paper.

The papermaking process begins with harvesting the bamboo at four o'clock in the morning.

At this time, the water content of the Tender Moso Bamboo is at its highest.

Next, a machete is used for peeling and splitting it into pieces.

Then, it is bundled and taken to the material hall.

This material hall is a pond. After the peeled and split bamboo is placed in the pond, lime powder is poured into the water using a wicker basket.

The process of soaking in water lasts for as long as forty-five days.

Only after the bamboo pieces are thoroughly soaked and turn yellow is the material gathered up.

Afterward comes the treading of the material, which is the most arduous step; it requires physical labor, as the material must be crushed under the soles of the feet.

It is crushed until it forms a pulp.

Only after the pulp is formed can the paper be screened.

Screening is the most technically demanding part of the entire papermaking process. Placing the paper fibers into a water tank and relying on experience to evenly scoop up a thin layer of pulp is called screening.

Then, the pulp is flipped and pressed onto a mold, and lifting the screen yields a sheet of wet paper.

A fire is lit, and the stove is used to dry the wet paper sheets one by one.

This is just a general overview of the ancient papermaking process.

The papermaking time takes nearly four months, and the complex techniques involve up to one hundred and eight steps. It has been refined by craftsmen over more than two thousand years and is extremely meticulous.

In the same ancient papermaking process, a difference of just a few steps in the procedure can lead to a huge disparity in the finished product.

For example, when Xishan Jade Paper was first interviewed by the public, it was said there were only twenty-eight steps, but in reality, there are as many as one hundred and eight.

These hidden steps cause a significant difference in the final product.

In today's highly developed industrial age, the reason handmade paper hasn't been phased out by machines—besides national protection—is largely because handmade paper is irreplaceable.

Handmade papermaking focuses on quality; every sheet is hand-selected, and the raw materials used are very pure, making the quality of the paper more high-end.

Handmade paper allows for better control over thickness, color, luster, and other aspects, making the paper more uniform.

Because handmade paper is dried at low temperatures, its smoothness is relatively low, it feels soft to the touch, and its density is lower. In contrast, machine-made paper is smoother, but its texture is hard and brittle.

This difference can be clearly felt when touched.

There is also a huge difference in the texture of the paper.

Due to its unique production process, handmade Xuan paper has a softer texture with a certain degree of toughness and elasticity. Machine-made paper, however, appears harder and more brittle, lacking this elasticity.

Zhao Fusu calculated that he must keep this papermaking method strictly confidential and not let it leak out.

The nobility would surely love this kind of paper.

Calligraphy and painting enthusiasts would certainly love it even more.

If he produced Xishan Jade Paper, he would definitely make money!

A smile appeared on Zhao Fusu's face.

After finishing the ancient papermaking method, Zhao Fusu got a headache again; for industrial papermaking, that acid solution would be difficult for him to obtain.

Wait!

A flash of inspiration suddenly crossed Zhao Fusu's mind.

If Xishan Jade Paper could be soaked and processed with lime powder, could lime powder also be used to make a solution?

Sure enough, as Zhao Fusu flipped through the book on industrial papermaking, he discovered that besides acidic solutions—which can accelerate the dissolution of wood to separate lignin and obtain pulp containing cellulose—alkaline solutions could do the same.

It was hard for him to get formic or acetic acid, but sodium hydroxide or calcium hydroxide—slaked lime—this stuff was cheap and easy to obtain.

Many nobles also used this stuff to whitewash walls, which could make them pure white.

He had solved the most difficult technical hurdle.

A smile appeared on Zhao Fusu's face.

He looked at the detailed introduction in the industrial papermaking section regarding the principle of lye cooking.

"Add an appropriate amount of sodium hydroxide or calcium hydroxide to the soaked raw materials and begin heating. At this point, the lye begins to take effect, dissolving the lignin and further softening and separating the fibers."

"Afterward, the raw materials are cooked in the lye for a period of time, usually several hours. During this process, as the temperature rises and time extends, the fibers are gradually released and suspended in the solution."

"Next is refining, where the fibers in the solution are further broken down and separated so that they can be more fully released."

"Finally, there is washing, where the solution obtained from lye cooking is washed multiple times to remove excess chemicals and other impurities."

Zhao Fusu looked at the key points of lye cooking.

Lye cooking is a very important step in the papermaking process, and it has a direct impact on the quality of the paper.

Among these, the concentration of the lye, the temperature, and the time have the greatest impact on the paper's performance.

For example, an excessively high lye concentration will cause the fiber layers to become disordered, reducing the paper's breathability and water resistance; an excessively low lye concentration will affect the paper's strength.

There were also corresponding regulations for the duration and temperature of the lye cooking.

Generally speaking, cooking for too long will cause the fibers to break down excessively, reducing the paper's strength.

If the cooking time is too short, too much non-cellulosic material will remain.

If the temperature is too high, the chemical substances in the fibers will be destroyed, reducing the paper's strength.

If the temperature is too low, it will affect the separation effect and the quality of the fibers.

Proper lye cooking operations can improve pulping efficiency and paper quality, which is crucial for the papermaking process.

To Zhao Fusu, these were all theoretical matters.

When he actually started practical operations, he would surely encounter many difficulties.

Zhao Fusu looked at the subsequent steps of industrial papermaking.

To make the paper whiter, factories would add fluorescent whitening agents.

However, while adding fluorescent whitening agents indeed makes the paper whiter and improves its appearance...

Fluorescent whitening agents have side effects; some people may have allergic reactions after contact, leading to skin ulceration or a 'fluorescent face'.

Zhao Fusu pondered slightly.

He should probably skip this step.

For one thing, he couldn't get his hands on fluorescent whitening agents.

For another, he could add clay or calcium carbonate for whitening.

Zhao Fusu continued reading.

"After the pulp is successfully made, moisture is removed through a series of roller presses. After drying, stretching, and smoothing, a continuous strip of paper is formed."

Knowing the process, Zhao Fusu immediately had someone call Zhang Han; he was going to designate an area specifically for papermaking.

"Head of State."

Zhang Han bowed with his hands cupped.