RHYTHMICALLY, men in white pharmacists’ coats stir a dark, thick substance that is brewing in wide copper pots. The liquid releases a vapor that is sucked up by a ventilation system on the high ceiling, and yet the room is filled with the mixture’s slightly bitter, herbal scent.

Chen Weiming walks around the pots to inspect the cooking and stirring progress, dipping a stick into the pots to test the liquid’s thickness.

He is on alert. Preparing gaofang, the popular Traditional Chinese Medicine paste, takes time, patience, and a lot of attention to detail, the 61-year-old expert says.

If everything goes well, he says, the decoction in the copper pots that’s already been soaked and boiled for two days will be done in just a few more hours. It will then be cooled and later sold as an expensive, jelly-like paste that promises to re-energize the body during the winter months.

Many Shanghainese who believe in TCM have already started their winter reinforcement therapy by mixing some of the paste with hot water and drinking it before breakfast each day.

Mass production has made the traditionally handmade paste more affordable and accessible to a larger number of people. It’s now one of the most popular reinforcement therapies, although it used to be reserved for the wealthiest members of society.

“Taking gaofang in winter was part of an elegant lifestyle in traditional Chinese culture,” Chen says.

But even today, price differences are significant. According to the ingredients, gaofang can be bought for as little as 2,000 yuan (US$308) for a jar that will last a month — the most common time-span for the therapy, while top quality, hand-stirred pastes with rare ingredients can set you back 10 times as much.

Chen has been producing gaofang for more than 30 years. Back then, he says, Shainghainese had a different awareness of their own health, and gaofang wasn’t as popular as it is today. For a handful of customers, Chen and his colleagues would produce no more than 1,000 jars.

He still works at Yueyang Hospital, where he learned the craft in the 1980s, but much has changed. “Back then, we had a dozen pots,” he says, his watchful eyes fixated on the apprentices. Today, the warehouse-like room with its high ceiling counts 80 copper pots in which at least 20,000 jars are produced throughout the year — an impressive figure, considering that Chen’s workshop is one of the last that stick to the centuries-old recipe and production process.

Even if mass production has helped make the remedy more popular, masters like Chen frown at it.

The perfect timing, which can only come with years of experience, is essential, as are the old copper pots and the hand stirring of the liquid.

“From my experience, there are some delicate details in gaofang production that cannot be replaced by machines.”

It’s an arduous process. Manually produced, it takes at least two and a half days until a gaofang is ready for the customer. It’s not that it’s difficult, Chen says — in fact, he describes the process as quite simple — but it requires great patience and exact compliance.

The herbs need to soak for at least six hours for their active ingredients to be released. The herbs are then transferred into a copper pot and cooked twice.

For years, Chen says that he never questioned why copper pots were used. “It was simply what my master taught me, and what was written in the TCM classics,” he says. But as mass production started, he looked into the copper pots and came across research that suggests that, as opposed to other material, copper is less likely to cause a chemical reaction during the long, high-temperature cooking process, which would contaminate the result.

Once the decoction is filtered, it is poured back into the copper pots and mixed with xi liao, which literally translates to “fine ingredients.” Depending on each customer’s prescription, xi liao is made of ginseng, seahorse, dear horn, aweto or other rare and expensive ingredients.

Once the xi liao are mixed with the herbal tonic, foam that forms on top has to be skimmed. It’s an important step that is often skipped in mass production, Chen says.

“Most of the mass-production lines omit this procedure for efficiency’s sake. But this makes the substance impure, and no good for the customer’s health,” he says.

Herbal thickeners like e jiao made of donkey skin, gui ban jiao made of tortoise plastron, yellow wine and brown sugar are then added. To ensure that all ingredients melt evenly, the workers have to keep stirring throughout the roughly 45-minute procedure until the mixture’s consistency is gooey.

His work has taught Chen patience, a virtue that makes him a pleasant and understanding master. But he still remembers being treated with relentless strictness during his own apprenticeship. One time, he failed to stir the decoction well, and his master found the substance uneven and too sticky toward the bottom. He was hit on the head three times.

“There’s no room for loaf on the job,” Chen says, a lesson he has learned over time.

Chen used to treat the production of gaofang like any other job, happy to clock-out at the end of the day. Today, he thinks of it as part of China’s heritage, a tradition that must not be lost. His whole heart, he says, is dedicated to it.

“It seems to be a practice of the procedure, but in fact, it is the pharmaceutical worker’s soul that is tested,” he says.

When he started, customers would invite gaofang masters to produce the past in their own homes, a way of making sure that they would get the expensive ingredients they were promised.

Today, Chen invites inquisitive customers to visit the workshop.

“I don’t know how I can dispel their doubts but to show them,” he says.

Still, hardly any customer will spend two and a half days to supervise the process, making it even more important that Chen teaches his apprentices respect for their profession.

Although he officially retired last year, he is still working at Yueyang Hospital. It’s not about the money, he says.

“Just imagining every sealed gaofang jar that is opened by a customer, the subtle herbal fragrance that is released into the air, that gives me great satisfaction,” he says. “That will make all my efforts worthwhile.”