A brick furnace with two and occasionally three large iron pots built into the center of the main deck of a whaling vessel, for the purpose of boiling down or "trying out" blubber. Located between the main and foremasts, the tryworks had a reservoir of water below its brick firebox to keep the heat from burning the wood of the deck. The first fire was fed by wood, but after the trying out was underway, tried-out scraps of blubber were used for fuel. Until the middle of the 18th century, colonial whalemen rendered, or extracted the oil, from blubber at the home port, or on the shore using portable try-works. This prevented whaling voyages from venturing far from shore or lasting more than a few weeks. The practice of installing the tryworks on the whaling vessel themselves transformed them into floating factories capable of cutting in, rendering and storing whale oil all in one place. This development lengthened the duration of whaling voyages substantially, allowing them to last for years and circumnavigate the globe in the pursuit of whales.