Composite iron/bronze cannons were far less common, but were produced in substantial numbers during the Ming and Qing dynasties. The resulting bronze-iron composite cannons were superior to iron or bronze cannons in many respects. They were lighter, stronger, longer lasting, and able to withstand more intensive explosive pressure. Chinese artisans also experimented with other variants such as cannons featuring wrought iron cores with cast iron exteriors. While inferior to their bronze-iron counterparts, these were considerably cheaper and more durable than standard iron cannons. Both types were met with success and were considered "among the best in the world" during the 17th century. The Chinese composite metal casting technique was effective enough that Portuguese imperial officials sought to employ Chinese gunsmiths for their cannon foundries in Goa, so that they could impart their methods for Portuguese weapons manufacturing. The Gujarats experimented with the same concept in 1545, the English at least by 1580, and Hollanders in 1629. However the effort required to produce these weapons prevented them from mass production. The Europeans essentially treated them as experimental products, resulting in very few surviving pieces today. Of the currently known extant composite metal cannons, there are 2 English, 2 Dutch, 12 Gujarati, and 48 from the Ming-Qing period.