Concretion of ceramics from the Hoi An shipwreck

WHAT IS THIS?
Over time conglomerations of material can form around objects in shipwrecks. In the photo you can see what this concretion looked like when it came into our collection.
With exposure to air internal materials made of iron began to oxidize and the entire concretion began to slowly fall apart. With this slow disintegration, unseen objects from the interior became exposed. On the adjacent labels you can see images of some of these objects and read what we are learning from them.
WHAT CAN IT TELL US?
As this concretion was exposed to oxygen, metal objects within it have begun to corrode. The shapes exposed suggest perhaps there was a metal chain inside the concretion.
One of the identifying features of Vietnamese ceramics of this period is the brown wash painted on the bottom of many pieces. Its purpose is still a mystery. One theory is that it was a method of marking the vessels that somehow kept track of the number of ceramics in a firing.

DELVE A LITTLE DEEPER…
Antlers were used in Southeast Asia for many purposes. Mature antlers could be used for knife handles, tools, and ornaments, while “antler velvet” was used for medicine.
This brick-shaped carved stone object is still a puzzle to us. Vietnamese scholars have not been able to identify it. Was it part of an altar or an incense burner?
Through the cracking surface of corroding material, a greenish color is evident, perhaps indicating a bronze or copper-alloy object inside the concretion. If the concretion falls apart even further, we may discover what this object is.
Deep within the concretion, a Chinese coin with its distinctive square hole can be seen by X-ray. Chinese coins were used throughout Southeast Asia.
t of an altar or an incense burn
CLUES FROM THE WRECKAGE
The ship was a hybrid Chinese–Southeast Asian model, perhaps made in Thailand.
The ship was large: approx. 30 meters long by 7 meters wide.
The hull was constructed with wooden dowels (a Southeast Asian technique) rather than nails (a Chinese method). The wood was teak, most likely from mainland Southeast Asia.
The hold was divided by partitions (bulkheads) into water-tight compartments, a characteristic of Chinese junks. The photo to the right shows a wreck with a hold of similar construction.

THE CARGO AND CREW
The ship contained a vast amount of Vietnamese export ceramics.
The crew was likely Southeast Asian.
The upper decks had storage jars for the crew’s use, primarily of Thai origin.
A skull of a woman, perhaps of Thai origin, was found.
One of the jars on the upper deck retained fish bones, perhaps indicating the storage of fish sauce, a staple of mainland Southeast Asian cooking.
Containers found on board stored ingredients for quids of betel, a mild stimulant used in much of Southeast Asia.