Across the 15th and 16th centuries there were primarily two different types of manufactured cannons. The wrought iron cannon and the cast-bronze cannon. Wrought iron guns were structurally composed of two layers: an inner tube of iron staves held together in a tight fit by an outer case of iron hoops. Bronze cannons on the other hand were cast in one piece similar to bells. The technique used in casting bronze cannons was so similar to the bell that the two were often looked upon as a connected enterprise.
Both iron and bronze cannons had their advantages and disadvantages. Forged iron cannons were up to ten times cheaper, but more unstable due to their piece built nature. Even without use, iron cannons were liable to rust away, while bronze cannons did not. Another reason for the dominance of bronze cannons was their aesthetic appeal. Because cannons were so important as displays of power and prestige, rulers liked to commission bronze cannons, which could be sculpted into fanciful designs containing artistic motifs or symbols. It was for all these reasons that the cast-bronze cannon became the preferred type by the late 1400s.
Some cannons cast in China during the 1370s may have been of steel rather than iron.