In laboratory 201.

"These pieces were fired before the improvement. Master has seen them all." Xing Yunlu skipped the first three pieces and pointed to the fourth piece, saying, "This was fired according to Master's instructions after finding high-quality white quartz sand."

"Well, it's indeed much more transparent." Zhao Hao nodded with satisfaction. The light transmittance of this piece was visibly improved compared to the previous three pieces.

"The fifth and sixth pieces are the same, but the quartz sand comes from different places." Xing Yunlu said: "At present, the quartz sand collected from Heshang Mountain in Huzhou Prefecture has the best effect."

"Yeah." Zhao Hao nodded. He really didn't know where the best quartz sand was. He could only rely on the research institute to keep searching and trying.

Xing Yunlu pointed to the seventh piece and said, "This is fired after the iron is removed."

Then he pointed to the eighth piece and said, "This is the one fired after removing iron and cleaning the quartz sand twice... By comparing, we can see that these two processes can indeed greatly improve the quality of glass. And we can also know that what the master said is correct. The purity of quartz sand does affect the quality of glass."

"Yeah." Zhao Hao didn't feel offended at all. Scientists should doubt everything and speak with experiments. This is the spirit he has repeatedly passed on to his disciples.

Young Master Zhao carefully pulled out the eighth piece of glass from the shelf and held it up to his eyes.

Then I saw that only a faint green color was left in the glass. I could also clearly see the freckles on Qu Rukui's face through the glass.

"Not bad, not bad, huge progress." Zhao Hao nodded with satisfaction, although it was still far from optical glass. Compared with the ninth piece on the shelf... the Western glass bought from the Portuguese in Macau, there was still a certain gap.

But it's only been a few months? The gap has already been narrowed to miles. There is no reason for him not to be confident.

"Master, it's too dusty here. Let's move on to the next step." Xing Yunlu was flattered by his master's praise and said while suppressing his excitement.

"Be sure to pay attention to protection, wear a mask, ensure ventilation, and eat black fungus every day." Zhao Hao nodded and gave a few more instructions. I believe that Xing Yunlu will strictly enforce all regulations as he is serious about it.

~~

Xing Yunlu lifted the door curtain again and invited the master to enter the purification room next door.

The purification room is divided into three rooms. The first one is used to extract potassium carbonate from wood ash.

The biggest difficulty in making glass with sand is that it is difficult to raise the furnace temperature to a temperature that can directly melt the sand. Later, the Venetians accidentally discovered that by adding natural soda from the salt lake, the melting point of the sand could be greatly reduced.

This was kept as a top secret by the Italians for more than 500 years. For this reason, they only produced glass on the isolated island of Murano. And the people on the island were not allowed to leave for generations.

This is also the reason why Taixi glass is expensive.

However, our ancestors knew as early as the Spring and Autumn Period that wood ash could also be used as a flux.

Originally, workers at the Glass Bureau poured wood ash directly into the sand, but this introduced too many impurities, greatly affecting the quality of the glass.

The chemical knowledge stored in Mr. Zhao's mind told him that the active ingredient in wood ash was potassium carbonate. Like sodium carbonate, potassium carbonate could be used as a flux when firing glass.

Moreover, potassium carbonate is a soluble salt substance, so Zhao Hao asked Xing Yunlu to dissolve the wood ash first, filter out the residue with a fine mesh, and then concentrate and crystallize it to obtain potassium carbonate crystals.

But everything is easier said than done. It took the laboratory nearly a month to come up with a full set of tools including filters and evaporators. We have just started the purification test and have not yet used it for firing.

So Zhao Hao didn't know whether this method would be helpful for burning glass. But purifying wood ash would not be a loss after all.

"This is a good stuff." Zhao Hao picked up a handful of white crystalline powder and showed a perverted smile.

With potassium carbonate, soap can be produced.

With soap, you can hehehe... it's not as dirty as you think, you can produce real explosives - yellow gunpowder!

But unfortunately, Master Zhao didn't even plan to take out the smokeless gunpowder too early, let alone the nitroglycerin gunpowder...

Thinking of this, he put away his smile and said to Zhang Jian behind him: "When Institute 04 is built, the purification work can be carried out in cooperation. Putting the research institutes together is for mutual cooperation and sharing of what we have."

"Yes, Master." Zhang Jian quickly wrote it down in his notebook.

The director of the research center is a person who doesn't care about anything, and the executive deputy director Gao Laohan is in charge of things other than research work. The business of the institute depends entirely on him, the deputy director, and no matter how good his memory is, he will inevitably miss something.

The second purification room purified the Glauber's salt brought back from Fengyang. Glauber's salt is used as a clarifier, which can greatly improve the transparency of glass.

The third purification chamber purifies quicklime, which not only has the function of fluxing, but also can adjust the material properties of the molten glass.

After leaving the purification room, we came to the material preparation workshop next to the kiln.

Then I saw the craftsmen pouring quartz sand into a wooden basin that looked like a bathtub. After washing it twice, they added auxiliary materials and then sent it into the kiln.

Although it was the coldest time of the year, the craftsmen beside the kiln were all shirtless and sweating profusely.

Zhao Hao also took off his cloak and looked inside through the furnace.

Then I saw that the quartz sand that had been put into the furnace built with Xishan Island's specialty refractory bricks had been melted into a bright yellow syrup-like state.

A craftsman inserts a five-foot iron pipe like a gun barrel into the furnace and spreads a thick ball of molten glass like dipping sauce. This step is called "picking materials."

The selected molten glass must be shaped within three minutes, otherwise it will solidify.

I saw the glass craftsman standing on a high platform, holding the iron pipe with both hands, putting his mouth to the end, taking a deep breath and blowing hard.

Blow a ball, blow a big leather ball...oh no, blow a big glass bubble.

The craftsman blows and rotates the iron pipe quickly, and the glass bubble slowly falls on the smooth iron plate, expanding outward under the action of centrifugal force to form a large disc with a smooth surface. Then the craftsman taps the lower end of the blow rod, and the glass is disconnected from the blow rod.

This step requires not only strong arm strength, but also very large lung capacity.

Don’t underestimate these few strokes. They are the result of years of hard work. In the entire Ming Dynasty, only the Liuli Bureau has craftsmen with such superb skills.

Zhao Hao spent 10,000 taels of silver to recruit these ten masters, and only half of them could blow glass.

At this time, the glass plate has begun to cool down and needs to be returned to the furnace to be softened. Then, a double-handled iron roller with a shiny surface is used to roll the glass plate evenly and flat like rolling dough. Finally, it is sent to the cooling furnace next door to cool down. After three days, it will become finished glass.

Zhao Hao couldn't wait that long. He felt like he was about to be roasted, so he left quickly.

ps. First update.