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Watertight Bulkhead Technology: The Junk Secret Franklin Admired

Intangible Cultural Heritage
Oct 9, 2026
Excavated Song dynasty Quanzhou ship hull with wooden bulkheads dividing it into compartments, displayed on steel supports in a museum hall

Watertight bulkhead technology is one of those ideas so obvious today that nobody asks where it came from. Split a hull into sealed rooms, and one hole no longer sinks the ship. Fujian’s junk builders worked this way for centuries. In 1785, Benjamin Franklin wrote about the Chinese practice and then admitted, a little sheepishly, “We have not imitated this practice” (Franklin, 1786). The West caught up. The craft that invented the idea, on the other hand, ended up on UNESCO’s urgent list in 2010. This guide explains how it works, how outsiders noticed it, and where you can still see it.

What Is Watertight Bulkhead Technology?

A bulkhead is a wall across the inside of a hull. Make that wall watertight, and you get separate compartments. If a reef or a collision opens one of them, the sea fills that room and stops there. The ship stays afloat (UNESCO, 2010a).

In Chinese, the heritage item is called 水密隔舱福船制造技艺, roughly “the craft of building watertight-compartment Fujian ships.” The nomination file also gives a plainer alternative name: craftsmanship for the construction of Fujianese junks (UNESCO, 2010b). So the UNESCO listing is not about a single invention in the abstract. It protects a whole way of building wooden ships by hand.

The materials behind the watertight bulkhead

According to the nomination file, the craft rests on a short, very local list of ingredients (UNESCO, 2010b):

  • Timber. Mainly camphor, pine and fir, ideally from trees at least 30 years old.
  • Joints. Planks are rabbet-jointed, then fixed to the bottom and frames or held with iron crampons.
  • Caulking. Ramie fibre, lime and tung oil, mixed and driven into every seam.
  • Tools. Axes, ink markers, hand drills, pit saws, chisels and planes — a carpenter’s kit, basically.

That caulk is the quiet hero. The file notes it is natural, strong and still used on some coastal fishing boats. Even so, the real knowledge sits in the head of one person: the Master Craftsman, who designs the ship and directs everyone else. There were no blueprints. Masters taught apprentices by voice and by example.

How Old Is Watertight Bulkhead Technology?

Honestly, nobody can pin down a birth date. China’s nomination file traces the technique back to the Jin dynasty (265–420 AD). China’s own heritage register says texts already describe divided sea-going hulls in the Tang, and finds show a mature system by the Song (China Intangible Cultural Heritage Network, n.d.). Early claims like these are hard to test. The hard evidence starts later.

The Quanzhou ship: thirteen rooms, one hull

In 1973, a wreck turned up in the mud of Quanzhou Bay. Archaeologists dug it out in the summer of 1974. Coins on board, the latest from 1272, suggest it sank a few years after that date. Twelve bulkheads split its hull into thirteen compartments (Wikipedia, 2026). The surviving hull is about 24 metres long; reconstructions put the full ship at roughly 34 metres.

Its cargo tells you where it had been. The holds held about 2.4 tonnes of incense wood, plus pepper, frankincense and ambergris. In other words, this was a working ship of the Maritime Silk Road, heading home to Quanzhou, the great Song and Yuan port. A Fujian provincial page calls it the largest and oldest seafaring ship ever found in China (Foreign Affairs Office of Fujian Provincial People’s Government, 2019).

How Outsiders Noticed Watertight Bulkheads

Here is the part that makes this heritage item unusual. Foreign visitors described it in writing, centuries apart.

Marco Polo and the hungry whale

One version of Marco Polo’s account, written around 1300, describes the big merchant ships of the eastern seas. The larger ones, it says, have “some thirteen compartments” made of strongly framed planking. If a ship springs a leak, sailors shift the cargo from the flooded room to its neighbours, fix the hole, and load up again. The cause of the leak? A rock, or — the text insists — a hungry whale ramming the hull at night (Polo, 1903). The whale part is, let’s say, doubtful. The thirteen rooms match the Quanzhou wreck rather neatly, though.

Benjamin Franklin’s nudge

Fast forward to August 1785. Franklin, sailing home from France, wrote a long letter full of ship ideas. He recalled “the well known practice of the Chinese” of dividing a great ship’s hold into separate chambers, each tightly caulked. Then he added the line quoted above. He even guessed why Europe resisted: a little lost stowage space. His counter-argument was commercial. Safer ships could win cheaper insurance and passengers willing to pay more (Franklin, 1786).

According to the nomination file, Western shipbuilders adopted the idea in the late 18th century, and it later became standard in modern ship design (UNESCO, 2010b). Exactly how much credit goes to Chinese examples, rather than parallel invention, is still argued. Still, the paper trail is clear. Europeans saw it in Chinese ships first and wrote it down.

A Western comparison: the idea won, the craft did not

Think of a modern ferry or cruise ship. Its steel bulkheads are welded, computer-modelled and checked by inspectors. The principle is the same one Fujian builders used. Yet almost nothing else carried over. No camphor wood, no lime-and-tung-oil caulk, no master shouting measurements from memory. That gap is the whole story of this UNESCO listing. The principle went global. Meanwhile, the hands-on craft stayed local and started to fade. For more Chinese ideas that travelled this way, see our tour of ancient Chinese science and technology.

Why UNESCO Put Watertight Bulkhead Technology on the Urgent List

The committee’s 2010 decision states the problem bluntly. Steel hulls replaced wooden ones, so demand for junks collapsed. And only three masters had full command of the craft (UNESCO, 2010c). The nomination file adds more detail (UNESCO, 2010b):

  • those three masters were all over 50, with about 60 other people involved in some part of the work;
  • most yards building wooden junks had closed;
  • good timber had become scarce and costly, and labour costs kept rising;
  • young people saw hard work and low pay, so few signed up.

The file names the core communities: Jinjiang City, especially Shenhu Town, and Zhangwan Town in the Jiaocheng District of Ningde. The three named transmitters were Chen Fangcai of Jinjiang, plus Liu Xixiu and Liu Zhaowei of Jiaocheng. China had already put the craft on its national list in 2008, as item VIII-138 (China Intangible Cultural Heritage Network, n.d.).

The Taiping Princess, and the plans after 2010

One project gave the craft a real boost. In 2007, Chen Fangcai was commissioned to design and build a 13-compartment, sail-only wooden junk named the Taiping Princess. According to the file, it sailed across the Pacific. The 2011–2015 plan then listed stipends, school visits, apprentice ceremonies, a seminar and even a replica of one of Zheng He’s treasure ships, with at least 3.34 million yuan pledged. How much of that list was completed is harder to check from public sources. So read it as a plan, not a scorecard.

More recent signs are modest but real. In 2024, a national news report quoted Yang Liangdun, a local transmitter of the craft, explaining how the sealed seams kept Fujian ships afloat (Liu, 2024). The craft, in short, still has living voices. Just not many.

Where to See Watertight Bulkhead Ships in Fujian

There is no working junk yard set up for tourists. Still, a curious visitor can get surprisingly close to this heritage in and around Fujian province.

  1. The Quanzhou Bay ancient ship gallery. The 1974 wreck sits in a pavilion on the grounds of Kaiyuan Temple, run by the Quanzhou Maritime Museum (Wikipedia, 2026). Look down into the hull and count the bulkheads yourself. It takes a minute, and it makes the whole idea click.
  2. The Quanzhou Maritime Museum main site. Its galleries cover the port’s trade and its ship models. General admission has long been free with a passport or ID. As of 2026, we could not confirm current hours or booking rules from an official page, so check the museum’s own channels before you go.
  3. Shenhu, Jinjiang. The nomination file says a boat museum opened here in 2008, with a model junk built by local craftsmen for the UNESCO file. Whether it keeps regular public hours now is unclear. Treat it as a side trip for keen ship fans, ideally with a local contact.

Pair the ship gallery with the sea rituals of the same coast. Our guide to the Wangchuan ceremony shows how Fujian communities still honour the ocean that these ships crossed.

Frequently Asked Questions

Did China invent watertight bulkhead technology?

China has the earliest well-documented examples, such as the 13th-century Quanzhou ship. Western writers like Franklin openly credited the Chinese practice.

What is a Fujian ship (fuchuan)?

It is the sea-going junk type of the Fujian coast. These ships typically had a narrow bottom and a broad upper hull, which made them stable on long voyages.

Are wooden junks still being built?

A few, mostly small coastal fishing boats, models and special projects. Large ocean-going junks are now rare, which is why the traditional watertight bulkhead technology counts as endangered.

Can visitors watch a junk being built?

Not on a fixed schedule. Museums in Quanzhou are the reliable option; workshop visits depend on local contacts.

A Good Idea That Outlived Its Makers

Every modern ship with sealed compartments carries a little of the watertight bulkhead technology story, whether its crew knows it or not. The irony is hard to miss. The principle conquered the world’s shipyards. Meanwhile, the wood, the caulk and the memorised know-how of Fujian’s masters shrank to a handful of people. That is why UNESCO calls it urgent. For more listed traditions like this one, browse our guide to intangible cultural heritage in China.

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