We don't know exactly when paper was first used in China but evidence from archaeological records indicate that it was prior to the first century AD.  In China, the most common source for paper was the bark of the paper mulberry tree (Gies & Gies 1994 p 182). Paper is made by tearing up rags, or the bark of trees or certain grasses and putting them into a large pot with water. The mixture is boiled and the pulplike mass that lies at the bottom is removed, strained and spread out to dry. Originally, paper was rough but, eventually over time, the making of paper was improved with sizing, dyes, and the use of molds made out of bamboo strips. Paper was first used by the Chinese for wrapping and it was not until the 3rd century that paper replaced bamboo, silk, and wood as a writing medium.

One of the most important developments in the Middle Ages was the experimentation and developments in iron production. As noted by Bert Hall in his essay, "Iron is one of the most useful metals ever discovered, but it is also one of the more difficult metals to understand in history, especially in medieval history. Iron comes in several forms, and the complications involved in producing each of them fosters further confusion."

One of the most elaborate clock towers was built by Su Sung and his associates in 1088 A.D.

nomenclatures