Chapter 322 is really amazing!

Apply several coats of black paint to the wooden board and let it dry naturally.

A simple blackboard is done.

In order to facilitate future teaching in the academy, Yun Fu made ten pieces at once.

"Xiao Fu'er, what is the purpose of making these black boards?" Qi Hanzhou was by her side the whole time, accompanying her in making these boards, suppressing his curiosity. Only after she finished everything did he ask her what these boards were used for.

Yun Fu explained to him, "This is called a blackboard. It's used for writing."

"Used for writing? If you want to write on a black board, you definitely can't use ink. I guess you need to make some special pens, right?" Qi Hanzhou drew inferences from one example.

Yun Fu nodded: "That's right, this blackboard is best written on with chalk."

The main material for making chalk is gypsum, the main component of which is calcium sulfate, a very common mineral.

Yunfu has made a surprising discovery recently. The special thing about the Ghost Prison is that it is extremely rich in mineral resources. There are black gold mines, iron mines and jade veins just a short distance away from the eighth-level area and the seventh-level area.

It shouldn't be difficult to find gypsum mines.

Gypsum is an ancient mineral Chinese medicinal material with the effects of clearing away heat and purging fire, relieving restlessness and thirst, and healing sores and promoting tissue regeneration.

Unfortunately, in the eighth-level area, there are not many people who understand medicinal herbs.

Yunfu specially drew a blueprint, describing in detail some important features of the gypsum raw stone, and asked people to make some inquiries in the eighth-level area. Within two days, they got the news.

The people here used to run almost all over the surrounding mountains to solve the problem of stuttering.

There are actually people who have seen this gypsum stone in the mountains.

"I've seen the white stone the princess mentioned. It's on the back of that mountain over there."

"Okay, if it's really plaster stone, I must credit you with this achievement."

Yun Fu asked him to lead the way and go take a look as soon as possible.

If it is really gypsum stone, it will have many uses in the future.

Chalk is just a trivial use of plaster.

They are lucky.

The white crystalline stone on the back mountain is actually gypsum stone.

Yun Fu deduced that this area, based on the characteristics of sedimentary gypsum deposits, would definitely not contain just one piece of gypsum. She would later arrange for people to search for and excavate more gypsum.

With the raw gypsum stone, chalk can be made.

Yun Fu personally smashed the gypsum raw stone she brought back into small pieces with a hammer, and then selected those with hard texture, no impurities, and low water content, and placed them in a dry and ventilated place to dry for a while.

Then pour the dried gypsum blocks into the mortar for grinding medicinal materials and crush them with a pestle.

Then change to a stone mill, place the grinding wheel on the table, add appropriate amount of water, and grind repeatedly until the gypsum stone is completely ground into fine powder.

After obtaining the gypsum powder, put the gypsum powder into the pot, add appropriate amount of water, heat and stir evenly, and stop heating when it is almost half dry and half wet.

Pour the semi-dry plaster into the mold, bake the surface of the mold, and when the chalk inside is sufficiently formed, remove it from the mold and let it dry.

Chalk made from pure gypsum powder without adding other substances is natural and pollution-free. It is also known as non-toxic chalk. Even if the dust dropped when writing is inhaled, it can be excreted from the body and will not remain in the human body.

Yunfu made dozens of boxes in one go, with a total of about 200 pieces of chalk.

It should be enough for the teachers in the academy to use for a while.

During the time the chalk was being made, several layers of black paint were applied, and the blackboard was left to dry completely.

Yunfu had the blackboard and chalk loaded onto a truck and shipped to the school.

It just so happened that Mu Yong and several teachers were there.

Seeing Yun Fu and the others transporting a cart of black boards on an ox cart, everyone looked at each other in confusion.

"What is the black plate on the princess's car used for? Does Dean Mu know?"

Mu Yong stroked his beard, his face full of pride. "I've never seen anything like this before, but I know that what Yun girl brought here must be something good. Just wait and see!"

Based on Mu Yong's understanding of Yunfu, this thing will definitely be of great use.

Yun Fu arranged for people to unload the large blackboards from the truck.

She also prepared the nails and hammer.

Have someone hang the blackboard on the wall.

Then he took out a piece of chalk from a small wooden box beside him.

Under the gaze of everyone, he raised his wrist and wrote his name on the blackboard with chalk.

Qi Hanzhou thought this blackboard and chalk were very novel, so he also took a piece of chalk and wrote his own name next to Yun Fu's name.

Staring at the two names close together, the corners of his mouth curled up in pleasure.

The two of them demonstrated it once, and Mu Yong and the other teachers understood what was going on.

"So these blackboards sent by the princess are to make it easier for us to teach those children."

"The black background and white words are so clear. Even the children sitting in the back can see them clearly." Unlike before, when I used water to write on the wooden board, I couldn't see clearly if I was a little far away.

Before he could say a few words, the word "water" disappeared.

"This blackboard and this white stick are so strange. Let me try them out."

Someone tried to pick up the chalk and left a line of poetry on the blackboard.

"This white stick is so easy to use. You don't have to keep dipping it in water."

Yun Fu cleared her throat. "You can call it chalk. It's made of plaster powder, and when you write, some powder will fall off. The point is, any piece of cloth can wipe off the chalk on the blackboard, so this blackboard is reusable."

After saying that, Yun Fu picked up a piece of cloth and wiped off her name.

This caused Mu Yong and the other teachers to exclaim in amazement.

"It's amazing how clean it is with just a piece of cloth. This blackboard and chalk are truly amazing!"

"Let me try, let me try!"

"I'll also use this chalk to write a few words on the blackboard."

Mu Yong felt sorry for the chalks: "Each of you should write a little less, just give it a try, don't waste these pens."

Yun Fu smiled and pointed at the dozens of boxes of chalk. "It's okay. There's still plenty here. It should be enough for you. I'll also write down the method for making chalk and leave it to you. If you don't have enough later, you can make your own."

Mu Yong touched the blackboard and said sincerely, "On behalf of those children, I would like to thank the princess for sending the blackboard and chalk."

"It's okay. I just happened to remember these things, so I made them." Yun Fu smiled and waved her hand, then continued, "Now that the teachers have the supplies, the next step is to find a way to get the children some paper and pens."