Based on different sources, paper making is thought to have originated in China in about 100 A.D. using grasses, rags and hemp as the raw material, and beating against stone mortars as the original fibre separation process. Although mechanization increased over the passing years, batch production methods and agricultural fibre sources remained in use until the 19th century. Continuous papermaking machines were patented at the turn of that century. Methods for pulping wood, a more abundant fibre source than rags and grasses, were developed between 1844 and 1884, and included mechanical abrasion as well as the soda, sulphite, and sulphate (kraft) chemical methods. These changes initiated the modern pulp and paper manufacturing era.