I Thought the Top Baozi Would Cook First. Then My Master Handed Me a Chopstick.

Ten Baskets of Baozi, Ripe from the Bottom Up

At half past five in the morning, Old Zhou's baozi shop had ten bamboo baskets stacked over the stove.

They rose in a column, one basket pressed on another, from the burner almost to the range hood. White steam pushed through every gap between the bamboo rims. The bottom baskets threw out thick streams. Higher up, the steam thinned into a pale mist. The bamboo looked dark and wet.

Xiao Chen set the last basket on top. "Master, which one gets ripe first?"

Old Zhou wrapped a towel around his hand. He pulled out the bottom basket and quickly pushed the one above it down. Steam hit his face.

"The bottom one."

Xiao Chen pointed at the lid. "Steam goes up. The top basket meets the steam first. Shouldn't the top one get ripe first?"

Old Zhou did not answer. He lifted the lid of the bottom basket. He stuck a chopstick into a baozi and pulled it out. The tip was clean. Then he lifted the top basket. He stuck the chopstick into a baozi and pulled it out. A small lump of wet dough clung to the tip.

"Taste it," Old Zhou said.

Xiao Chen broke open a baozi from the bottom basket. The skin was soft. The filling burned his tongue. He broke open one from the top. The skin stuck to his teeth.

"Why?"

Old Zhou put the lids back. He pointed at the water in the pot.

"Water boils. It turns into steam. Steam enters the first basket. The baozi there are cold. Steam touches them and condenses. Condensation gives off heat. That heat cooks the baozi. Every basket takes some steam and some heat. By the tenth basket, the steam has less strength."

Xiao Chen watched the gaps. The bottom baskets threw out thick white streams. The top had a thin mist. Water beads hung on the lid and dropped one by one.

"So the top gets tail steam," Xiao Chen said.

"Tail steam," Old Zhou said. "And the lid loses heat to the air. Up there, less steam. The heat does not stay."

Xiao Chen took out his phone. He searched for a moment.

"Someone says a steamer is a sieve plate distillation column. Reboiler at the bottom. No condenser at the top. Closer to the reboiler means higher temperature. So lower baskets get ripe first."

Old Zhou moved an empty basket down. He wiped the bamboo slats with a rag.

"A distillation column has reflux," he said. "It has a condenser at the top. The condensate returns down. A steamer has no reflux. The baozi do not separate into light and heavy components. Steam goes up. It condenses layer by layer. It gives off heat layer by layer. You can call it a column. It works like a series of heat exchangers."

Xiao Chen typed "series of heat exchangers" into his phone. Then he read from the screen.

"Water turning to steam at 100 degrees Celsius carries about 2,260 kilojoules per kilogram. Water cooling by one degree gives up about 4.2 kilojoules. Condensation is hundreds of times stronger."

Old Zhou nodded. "That is why steam cooks fast. Steam carries heat when it changes back to water. Hot air does not carry that much heat."

Xiao Chen looked at the stack again. "Does pressure matter?"

"A little," Old Zhou said. "The steam loses some pressure as it climbs. Saturated steam at lower pressure has a slightly lower temperature. In the kitchen, you do not measure it. You watch the steam. You listen to the basket. You tap the lid."

He tapped the bottom basket with his knuckles. It gave a hollow sound. He tapped the top basket. It gave a dull sound.

"The TV station did an experiment," Old Zhou said. "Same size baozi. Numbered. Steamed in one pot. The bottom ones got ripe first. The fire is under the pot. The steam starts at the water. The bottom basket sits closest to that steam. That is why it gets ripe first."

Xiao Chen asked, "So the top ones get ripe last. Can they be undercooked?"

"They can," Old Zhou said. "So you cannot stack ten baskets and walk away. You rotate them."

He pulled the top basket down. He put it at the bottom. He put the old bottom basket on top. Steam moved through the stack again. The new bottom basket began to take heat. The old top basket got a rest.

"The bottom gets ripe first, and it can overcook," Old Zhou said. He patted the bottom basket. "Too much steam. Condensate drips. The bottom of the baozi gets sticky. The top gets ripe last. The skin can dry out. The middle baskets sell best."

Xiao Chen watched the ten baskets settle into their new order. Steam came through the gaps. The bottom few turned hard and fast. The top one waited.

"Did the CCTV experiment say how big the difference is?" Xiao Chen asked.

"How big depends on the fire, the baskets, the size of the baozi," Old Zhou said. "Two or three baskets, sealed well, high fire, they might get ripe almost together. Ten baskets this high, the bottom will get ripe first."

Xiao Chen put his phone away. He tapped the lid with a chopstick. The top basket sounded dull. The bottom basket sounded hollow.

"Tomorrow I will come early and pull the bottom first," he said.

Old Zhou turned the fire down a little.

"See you tomorrow."

The shop smelled of pork, scallion, ginger, and wet bamboo. A customer came in at six. He asked for two baozi from the middle basket. Old Zhou opened the third basket from the top. The customer took the bag and walked into the gray morning.

Xiao Chen wrote on his notepad: bottom first, top last, middle best. He drew ten circles in a column. He marked the bottom with a B. He marked the top with a T. In the middle he wrote M.

Old Zhou saw the notepad. He laughed once, without sound.

"You draw it. Your hands still have to learn it."

The water in the pot kept boiling. The steam kept climbing. Each basket took its share. The bottom took the most. The top took what was left. The lid let heat into the air. The bamboo held heat in its grain. The baozi sat in rows, white and round, waiting to be taken out at different times.

At seven, the breakfast rush came. Xiao Chen pulled the bottom basket, then the second, then the third. He moved the top baskets down. He watched the steam. When the bottom streams turned thin and fast, the baozi there were close. When the top mist barely showed, the baozi there were not.

He did not say "distillation" again. He had the pot, the steam, the baskets, the chopstick, and the old man's hand on the fire. That was enough for the morning.