Xia Yu didn't reply, he had already learned the assessment criteria from Mrs. Huang.

The energy efficiency of 80% is actually the source energy conversion efficiency, which is an indicator of the degree to which the source box can convert the source energy in the source crystal.

80% is relative to the standard, which is set by the Association of Federal Teachers, which is quite difficult.

The source box purchased on the market can generally reach 90% of the standard, and it will be a little difficult to improve it later.

More than 95% is considered a high-quality product, and reaching 100% of the standard can be called perfect.

There are even those that exceed the standard, but those are all realms that can only be reached by true masters, and ordinary people can't reach them.

Xia Yu first had to take the low-level organ apprenticeship, so he only needed to make a source box that reached 85% to pass the level, and the difficulty was not too great. In the middle tier, you need to have at least 3 different types of crates on a 1-star crate to reach 90%, and you can make an 85% 2-star crate at the same time.

As for the high tiers, it is necessary to craft 3 1-star source crates that reach 95% of the standard efficiency, and one 2-star source crate that is 90% effective.

Xia Yu is not sure now.

When he was chased and killed by Cui Dalong, his perception broke through again, and his tentacles had reached 17, and his strength had reached nearly 4 meters.

And during the physical recuperation of the past month, he spent most of his time studying various source arrays and source boxes, and the research target was also reduced from the previous 1 star to 2 stars.

The structure of a 2-star source array is much more complex than that of a 1-star.

Just like a flat figure and a three-dimensional figure, it takes an extra layer of dimension, and it is much more difficult to build a stable specific functional structure.

Fortunately, Xia Yu knew his advantage, and under the 17 perceptual tentacles, his understanding of the source array was very fast.

After reaching the level of perception, he could almost quickly comprehend the various source boxes in Lao Chen's repair shop, and even tried to adjust those structures by himself very early.

However, his current favorite 2-star trap, "Yao Sun", has never been understood.

Once when the interest came, he studied the "Yaosun" source box for a whole afternoon, and only felt that the structure of the source array was very complex, brilliant, and mysterious, and the part of his understanding was less than 10%, and only some breakpoint-like lines appeared in his mind each time, and they quickly disintegrated and dissipated.

Even, just the texture of the appearance of the "Dawn Sun" source box made him feel very magical.

This made him feel that his level was still very low.

Of course, the real test of the apprenticeship assessment is not to understand the structure of the source array, but to use specific materials to make the source box, skills, proficiency, etc.

Mrs. Huang couldn't teach these things, and she didn't have the time, so he took one or two very brief books to ponder by himself, and later only bought some jade yin sand and practiced for a while.

So he didn't dare to think about taking the high-level apprenticeship exam at once.

Gently pouring some jade yin sand into the pottery dish from a transparent jar, Xia Yu began to grind the jade yin sand.

Jade Yin Sand, also known as Yellow Yin Sand, is a special ore particle, which is yellow in sunlight and is one of the most valuable associated ores of source crystals, and is currently widely used as a material for the production of source boxes for medium and low star organs.

This sand is not a metal, but it is much more special than common jade, and is basically only produced with the source crystal.

Each grain is an individual crystal, the size of a grain of rice, which looks crystal clear, and when ground and crushed, it will turn into a finer independent crystal.

These subtle crystals are very sensitive to perception and energy, and when combined, they can "carry" the source array structure - after all, the source array is built in the human mind, and only this incomparably subtle material that maintains an independent crystal structure can "carry" the source array and can be triggered by human perception.

In addition to jade yin sand, common source box production materials such as gray crystal sand and linlong sand have this special structure.

"It's another freshman, and I still want to take the intermediate level at this level, it's really a big dog!"

Here, looking at Xia Yu's obviously somewhat rusty grinding action, the white-clothed steward was a little disdainful in his heart, and soon stopped paying attention to him, took out a book and looked at it himself.

The market price of an ordinary second-order source box is hundreds of nearly thousand euros, but the raw materials are generally about three or four hundred, and the assessment of the organ association provides three materials for each source box, and the intermediate assessment charges 2,200 euros, which is also a profiteering business.

Some people from poor families are not absolutely sure that they will never waste the money in this assessment.

Xia Yu didn't care about him, and patiently polished the jade yin sand with a grinding pestle, and after ten minutes, the jade yin sand in the pottery dish was close to powder.

Seeing that the grinding was almost done, he carefully placed all the jade Yin sand powder in a special heat-resistant plate and put it into the source energy heat meter on the side.

Then, he urged the perception, slowly raised the temperature to about 1700 degrees, and then through the magnified observation window of the thermometer, he carefully observed the changes in the jade yin sand powder in the heat-resistant plate, and adjusted the perception control temperature to ensure the formation of the jade yin gum.

Glue making is the second step in the production of source boxes, and it is also a step that tests the precise control and production experience.

Because of its special structure, even if it is ground into powder, each powder of Yuyin sand is an independent crystal.

When the particles are small enough, they can exhibit different viscosity at different temperatures, which is called jade yin gum, which is suitable for source array structures with different characteristics.

Xia Yu's first attempt was a common temperature-controlled source array, which required relatively delicate jade Yin glue.

After the summary of many senior masters, the jade yin sand powder with a diameter of about 1 mm and a temperature of about 1700 degrees is more suitable for this source array.

However, the specific operation also depends on the size of the jade Yin crystal particles at the time of production to determine the most suitable temperature.

If grinding is the simplest preparation step in the production of the source box, then glue making is a meticulous work, which requires fine perception to control the subtle changes of each degree of the thermometer, and also requires a certain amount of experience to make judgments.

As long as these are mastered, we can make the best quality jade yin glue that is most suitable for perception and energy sensitivity in continuous attempts.

"Not to mention, this exam costs a lot of money, at least the accuracy of the thermometer provided by the People's Organ Association is really high, at least 2 levels higher than the one that Lao Chen is doing in the repair shop!"

With 17 sensory tentacles, Xia Yu is still very strong in temperature control.

However, to evaluate whether the jade Yin glue is perfect, it completely depends on the experience of the mechanic, after all, he has too little experience, and roughly estimates that it is okay, so he stopped the glue making work, calmed down his perception a little, and then began to carry out the key step: condensation.

This step is also done in the thermometer.

When condensing, it is necessary to fix the temperature in the most suitable state, and then directly use the sensing cyclone to construct the source array structure in the mind, and then connect it to the jade yin gum through perception. At this time, the unique perceptual sensitivity of jade injiao will come into play, and the fine crystals inside it will be reorganized according to the source array structure.

After the reorganization is over, it is stabilized, and this source box is mostly completed.

The last step is to make the jade yin glue that already has a new structure inside into a suitable shape, and then draw some lines on it to communicate energy.

These source patterns are all derived from the source array structure, which can be regarded as some supplements.

Grinding, glue-making, coagulation, and pattern painting - these are the four major production steps of a source box.