Song Yingxing wrote that ancient rulers of early China cast inscriptions of writing onto bronze tripods since this was a much more durable method of preserving the written record than using the perishable materials found in books and scrolls.Song, 159-160. He noted that musical and announcing bells of higher quality were made of different copper alloys, while those of lesser quality were made of iron.Song, 160. He also provided weighted formulas of different metal compositions for certain bells, for example, the casting a large bell in an audience hall or pavilion that required 47,000 catties of copper, 4,000 catties of tin, 50 oz. of gold, and 120 oz. of silver in its composition. In the smelting process, long pits for the liquid metal flow had to be dug, having a drymold construction of lime and mortar that was dried and covered in ox fat and beeswax. Then he noted the following process of pounded earth and charcoal powder that was screened and mixed into a mud paste that would be gradually spread on the surface of the wax several inches thick.Song 162. When dried and heated so that the melted fat and wax could flow out entirely by means of apertures at the base, the bell or tripod could be cast in the vacated cavity between the core and the mold. With the individual casting process for bells and tripods, Song Yingxing also described the intricate individual casting processes for making cooking pots and pans,Song, 163. metal statues, metal barrels of cannons,Song, 165. metallic mirrors, and different metallic coins of copper or iron.Song, 165-169. He described the processes of hammer forging with the initial casting of an anvil, and noted that in the heating process of forging, coal accounted for 70% of the fuel, charcoal taking the rest at 30%. He also outlined the quench-hardening process of rapid cooling in clear water immediately after iron and steel products were forged.Song, 190. He outlined the different types of knives, axes, hoes,Song, 191. file tools, awls,Song, 192. saws, wood chisels,Song, 196. anchors, and metal needlesSong, 196-197 that could be forged and produced. For the making of the finest swords, he said, they are coated with steel after "a hundred smeltings," but the core of the sword was still made of wrought iron; this was because a sword made entirely of steel would easily break when making hard strikes.
