"I memorized it."
Old Hope gave a cold laugh and put down his coffee cup.
What are the proportions of alum, salt, and water in the tanning solution for summer-harvested black-tailed deer pelts made from juvenile black-tailed deer?
This is an extremely tricky question.
The notes contain hundreds of recipes, with slight variations in proportions for different species, ages, and seasons.
Su Wei did not hesitate at all.
"700 grams of alum, 350 grams of salt, and 4 liters of water. Additionally, 20 milliliters of formic acid need to be added as a softener, because the hides of young deer are thin and lack toughness."
Old Hope paused for a moment.
He squinted and continued asking questions.
What is the purpose of the first step, degreasing and soaking, when processing otter pelts? What are the consequences of omitting this step?
"Otters have a thick layer of subcutaneous fat, rich in protective oils. Without degreasing, the tanning solution cannot penetrate evenly, leading to internal rotting and external stiffness of the pelt—a condition known in the trade as 'false tanning.' Within six months at most, the hair follicles will loosen, and large-scale hair loss will begin."
Su Wei answered fluently, as if that knowledge had been engraved into his very bones.
Old Hope fell silent.
He stared at Su Wei, his face devoid of any emotion.
For a moment, only the hum of the exhaust fans remained in the factory.
After a full half minute, Old Hope finally stood up from the bar stool and walked silently to the workbench in the corner, which was piled with bottles and jars.
"Come over."
He gave the order without turning his head.
Su Wei followed.
On the workbench were a dozen or so glass beakers and graduated cylinders of different sizes, along with an electronic scale, a stirring rod, and brown bottles labeled with various chemicals.
"The preparation of the tanning solution is the core of specimen preparation. Even a one-thousandth error in the proportion can ruin a perfect piece of skin."
Old Hope's voice was hoarse.
I'll only do it once.
"I saw it clearly."
Before he finished speaking, his hand moved.
Those were hands covered in calluses and scars, yet their movements were astonishingly fast.
He didn't even use an electronic scale; he grabbed a handful of white alum crystals, weighed them in his hand, and poured them directly into a large glass container filled with water.
He picked up the salt shaker and sprinkled some salt on the ground.
The entire process was efficient and without any unnecessary delays.
He picked up a long glass rod and began to stir.
The liquid changes from clear to cloudy, and then slowly becomes transparent again.
"The speed and duration of stirring determine the uniformity of dissolution. Too fast, and bubbles will form, affecting penetration. Too slow, and crystals will settle to the bottom, resulting in uneven concentration."
He kept talking, but his hands never stopped moving.
He then opened a pungent brown bottle, used a dropper to draw a small amount of liquid, and added it to the solution.
"Formic acid, used for softening. Too much will burn the skin. Too little is useless."
The entire demonstration lasted no more than five minutes.
Old Hope threw down the stirring rod, which made a crisp sound as it struck the side of the container.
He pointed to something soaking in a sink next to him.
It was a complete piece of leather, still dripping with water.
Judging from its size and fur color, it is the otter that Su Wei skinned yesterday.
"Now, you come."
Old Hope stood with his arms crossed, leaning against a shelf, looking like he was waiting to see a good show.
This is not teaching at all.
This is pure harassment.
There are no precise measurements, it's all based on intuition, and the demonstration is quick.
But Su Wei remained calm.
He put on thick rubber gloves and stepped forward.
Every move and every detail of Old Hope's actions was clearly imprinted in his mind.
More importantly, he had the precise formula in his mind.
Instead of grabbing it with his hands like Old Hope did, Su Wei took a clean beaker, placed it on the electronic scale, and zeroed it.
Then, he poured the alum granules into a beaker until the number on the electronic scale accurately jumped to the amount of grams required by the recipe.
The same applies to table salt.
Old Hope let out a disdainful snort.
Su Wei knew that, in Old Hope's view, relying on tools was the mark of an apprentice; a true master's hand was the scale.
Su Wei ignored him.
He poured the weighed ingredients into the water one by one, picked up a glass rod, and began to stir.
The passive skill of the Life Module - Nimble Hands - comes into play at this time.
His wrist was exceptionally steady, and he stirred the water at a moderate speed, creating a uniform vortex.
He could even feel how the tiny crystals in the solution dissolved and diffused little by little, driven by the water flow.
His keen awareness of subtle changes in matter captivated him.
Finally, formic acid is added drop by drop.
He used a dropper to precisely draw the dosage required by the formula, adding it slowly, drop by drop, into the solution.
When the last drop of liquid was incorporated, the entire basin of tanning liquid took on a translucent milky white color.
It's done.
Su Wei took the otter pelt he had peeled off yesterday out of the trough, wrung out the excess water, and then slowly immersed it in the tanning solution he had prepared himself.
When the skin was submerged in water, it stretched out without the slightest sign of shrinking or stiffness.
A message that only he could see appeared before his eyes.
[You have successfully prepared and used one batch of basic alum tanning solution.]
[ Preservation Treatment LV2 Experience +10.]
[You have gained a new understanding of chemical tanning.]
Su Wei straightened up and looked at Old Hope, who was leaning against the shelf.
Old Hope came over.
He didn't say anything, but simply extended two fingers, dipped them into the basin of tanning liquid, and smelled them.
Su Wei noticed that his brow twitched almost imperceptibly.
The saltiness and acidity are just right.
This kid isn't just imitating; he genuinely understands.
Old Hope used a greasy rag to wipe the remaining liquid off his gloves.
He walked around the basin of tanning liquid, seemingly trying to find something wrong, but ultimately said nothing.
The factory fell into that suffocating silence once again.
Su Wei could hear his own heartbeat.
After a long while, Old Hope finally spoke, his voice hoarse and devoid of emotion.
"You can start assisting me now."
Chapter 139 Fishing Invitation
Old Hope's words went unheard in the factory filled with the smell of medicine, but they stirred a ripple in Su Wei's heart.
This is approval.
There was no praise, not even a change in emotion.
Old Hope was simply stating a fact: this was Su Wei achieved through their own abilities.
Su Wei didn't show any extra emotion; he simply took off his coat and put on a heavy leather apron stained with oil.
Old Hope, his back hunched, walked deep into the factory, where there stood a huge stainless steel operating table, twice the size of a regular operating table.
He pressed a switch on the wall, and a row of shadowless lights above the control panel instantly lit up, illuminating the stainless steel surface with a bright white light that made every scratch clearly visible.