Smooth as silk

Part four in a series from China

“Smooth as silk,” it seems, isn’t as smooth as I’ve always been lead to believe.

“Is little rougher than polyester,” our guide tells us. “Has texture.”

She’s standing in front of us in a small, neat seminar room at the No. 1 Silk Factory. She has passed around two cloth samples: one made of silk and one made of polyester, and she’s challenged us to tell the difference.

Sure enough, one of them is smooth as silk and the other is slightly less so.

“Polyester also shinier,” she says. “Also, it flammable. Anyone have lighter?” she asks. Remarkably, in a room full of graduate students, no one does. Our guide pats the pockets of her brown business suit, but she comes up empty, too. “Silk not burn. Fireproof,” she says.

Her demonstration has worked in the past, though. One of the samples, the smoother, shinier one, has several holes burned into it. When she asks again if we can tell which sample is the polyester, one of the students, Jerry, holds it up. “The one with the burn holes in it,” he says. His classmates laugh.

With Jerry’s guess, the silkworm’s now out of the bag, so it’s time to start our tour of the factory floor to learn how silk is made.

For centuries, silk has been one of China’s most famous exports. Traders coveted it so much they trekked across the sands of Persia and braved the Himalayas to open a trade route—the Silk Road—that stretched from the Mediterranean to the ancient Chinese capital of Xi’an and, from there, into China’s interior.

Our guide has ten thin glass specimen jars lined up in front of her. Each contains a silk worm at a various stage in its development. There are male and female moths—the females are bigger—eggs the size of pin heads, larvae of several sizes, from newly hatched “ant larvae” to a bulging fat 25-day-old, and a silk-shrouded pupa.

From the seminar room, she leads us past a small garden of mulberry plants. Similar patches of mulberry grow all over the countryside around Suzhou, around farmhouses and along the “crisscrossed footpaths between fields,” she says.

Mulberry is for silkworms what bamboo is to pandas or eucalyptus is to koalas. Perhaps a better example, I think, is what milkweed is to monarch butterflies. After all, silkworms have more in common with monarchs than with either species of cute, cuddly-looking fake bear.

People harvest the mulberry then raise the silkworm caterpillars in their homes. Silkworms, it turns out, are fussy houseguests. They have to have a special room that’s kept dry—and if the mulberry leaves get wet, in the rain for instance, they have to be wiped dry so the silkworms don’t accidentally drown on their food. They’re also highly susceptible to perfumes and cosmetics and even the grease off people’s skin.

That doesn’t stop my students from picking up silkworms when we find a wide, pan-like basket of them in the next room on the tour. The baskets are filled with mulberry leaves that are literally crawling with hundreds of silkworms. The students gather around in a mixture of interest and grossed-outness, and our guide encourages people to handle the larvae. Put like that—“Handle the larvae”—it doesn’t sound quite so fun.

If the larvae survive the gamut of handling, perfume, and rainwater, and they reach 25 days old or so, they’ll spin their cocoons. Each silkworm can spit out enough silk to create a filament about a mile long. It’ll take two or three days to complete the job, but when they do, they’ll have each wrapped themselves in a pocket of silk.

The silk farmers will collect straw that they’ll weave into frames that the silkworms can use to anchor their cocoons to. The straw frames also make harvesting easier.

The process of raising silkworms for their silk is called sericulture, and it’s been practiced in China for 5,000 years. The No. 1 Silk Factory isn’t that old of course; it was built in 1926, so in relative terms, it’s still just a larva. But it gets its claim to fame for being the first commercial enterprise to open itself for tourists. It’s now a state-run factory that employs more than 300 people who work 8-5, five days a week.

Aside from our guide, it’s been all worms and no workers, but we see our first one in the next room. A conveyor belt rolls cocoons past a woman who grades them by color. The white ones get passed along for eventual use as thread for weaving. Slightly yellowed cocoons get sorted out and used for silk quilts. Anything that’s really discolored or spotty or thin gets tossed.

From there, the cocoons get cooked in something that sounds like it comes right out of Dr. Seuss: “a circulating stainless steel cocoon-cooking machine.” The half-hour soaking boils away much of the silk’s gumminess, which makes the cocoons easier to unspool. Then an automated brusher goes over the surface of each cocoon to find the end of the filament. Each filament is only one-seventh the thickness of a human hair, so eight of them are bound together to make a single thread.

We walk past two banks of machines where middle-aged women, their hair plastered to their scalps by all the steam, go about their business as though they don’t have a group of people gaping over their shoulders.

In front of them, the cooked cocoons float in a long trough of water, grouped together in bundles of eight. The women thread the ends of the eight filaments through a machine that reels the strands together into a single thread. As the machine runs, each cocoon unspools like a top, bobbing manically in the water as the women supervise.

When a cocoon exhausts its silk, one of the women moves in to add a replacement so that the thread always has eight filaments to it. The corpse of the pupa, meanwhile, still shrouded by a nearly transparent sheet of silk, gets plunked into a nearby stainless steel bowl.

The women work there mostly for show, I think. Further down, a machine does the work of half a dozen of the women. It’s all hot water and spinning brushes and clattering gears and humming belts, like something from a steampunk novel. The guide later tells me that much of the operation in automated because they operate on such a large scale, but the factory tour still shows the old way because “is more interesting for visitors.” Most of the real production takes place at a different facility, which No. 1 Silk Factory keeps closed to the public. “Don’t want to give away secrets,” the guide tells me.

The reels of silk are then re-reeled to get the moisture out. The process also strengthens the threads while making them more elastic. Once re-reeled, the silk looks like long locks of Rapunzel’s white hair. It can then be boxed up for later processing.

Mulberry bushes only grow from April through October, so the factory uses “fresh” silk while its in season and then, in the off season, it’ll start cracking open boxes of the re-reeled silk from the previous year. They have automated looms that do the actual weaving, using plates similar to the old-style computer punch cards to guide the pattern for each pass of the shuttle through the loom. It can take up to 10,000 plates to complete one pattern.

“So intricate, it can only weave about five meter a day,” our guide says. The new, computerized looms can go much quicker, producing 100 meters a day.

In the last room, a woman is soaking B-grade cocoons and cracking them open, peeling the pupae out and stretching the cocoons over a small arch-shaped frame. When she has ten cocoons stretched out, she takes the entire bunch and stretched them over an even larger arch. There’s strength in numbers, apparently.

Our guide removes the silk stretched over the big frame and invites several of the students to grab it by the edges. “Stretch it out, carefully,” she instructs. The students slowly pull the silk until it’s wide and thin and spider-webby. She has them lay it on a pile of similarly stretched silk. “This will be used for quilt,” she says, and it suddenly becomes obvious that the students have just stretched their silk into a mattress-sized rectangle. It’ll get sewn into a cotton cover and sold in the factory gift shop.

And, indeed, there is a gift shop. It features Choyers brand silk products: everything from quilts to dresses to ties to silk screens with calligraphy and artwork painted on them. Several of the guys find themselves in the audience for a fashion show that shows off many of the clothes, although I’m not sure that’s what the guys are interested in.

My last encounter with the silkworms, though, comes a couple days later, at a huge buffet in Beijing. Among the hundreds of menu items, under a heat lamp next to a basket of locusts sits a basket of crisped silkworms. I pick up a few with my chopsticks, just so I can say I tried them.

They don’t taste like much, really. But with a little beer as a chaser, they go down smooth as silk.

4 replies »

  1. Your tour guide was having you on, you know.

    Silk burns easily, usually not with a full flame, smells just like burning hair and has a crumbly ash. Polyester burns and melts at the same time, can smell sickly-sweet and the residue is sticky, then hardens.

    Unless they treat their silk with asbestos (and they don’t), I wouldn’t try a burn test on any pajamas you may have bought.

  2. Hey, I just report the story as I see it. I did follow up on the burning silk thing, although I didn’t put it in the story because she never got to demonstrate it. She did demonstrate it last year and, indeed, the silk didn’t burn. Near as I can tell, silk IS flammable, but compared to other fabrics, it’s the least flammable. It needs to be held over a constant flame to catch, and even then, it won’t go “poof” up in flames. I think her secret last year was that she didn’t hold the lighter on one spot; she sort of passed it over the surface so it wouldn’t concentrate in one spot for any length of time.

    As for the silk pajamas…alas, I passed!

  3. It’s true, proteins are the least flammable among the natural fibers, but several synthetics are much, much less flammable… and slower to ignite. And as soon as you treat and dye a protein fiber, the ignition and flammability rates shoot right up there with cellulosics.

    But yes, she did her trick by moving the flame quickly over a tight-weave, minimally-processed fabric; the less airspace among the fibers, the slower any fabric will burn, and the more natural worm spit remaining on silk, the more flame-resistant it is. Hold a lighter to any of those pretty, colorful souvenirs, though, and watch out.

  4. I will second that she is putting you on. I have done burn tests on wool that I was going to spin to see what was contained in the roving, and silk does indeed burn, and stink.

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