If iron ores are heated with carbon to 1420–1470 K, a molten liquid is formed, an alloy of about 96.5% iron and 3.5% carbon. This product is strong, can be cast into intricate shapes, but is too brittle to be worked, unless the product is "decarburized" to remove most of the carbon. The vast majority of Chinese iron manufacture, from the late Zhou dynasty onward, was of cast iron. However forged swords began to be made in the Warring-States-period: "Earliest iron and steel Jian also appear, made by the earliest and most basic forging and folding techniques."