- Blast Furnace
Chinese smelting begins with bronze.
The oldest known blast furnaces were built during the Han Dynasty of China in the fourth century B.C.E. Early blast furnace production of cast iron evolved from furnaces used to melt bronze. lron was essential to military success by the time the State of Qin ad unified China (221 B.C.E). By the eleventh century C.E. the Song Dynasty Chinese iron industry switched from using charcoal to coal for casting iron and steel, saving thousands of acres of woodland.
In a blast furnace, fuel and ore are supplied through the top of the furnace, while air is blown into the bottom of the chamber. The chemical reaction takes place as the material moves downward, producing molten metal and slag at the bottom, with flue games exiting from the top of the furnace.
The oldest known blast furnaces in the West were built in Durstel in Switzerland, the Markische Sauer land in Germany, and Lapphyttan in Sweden, where they were active between 1150 and 1350 C.E. There have also been traces of blast furnaces dated as early as 1100 found in Noraskog, also in Sweden. These furnaces were very inefficient compared to those used today.
French Cistercian monks, who are known to have been skilled metallurgists, passed on their knowledge of technological advances regarding Blast furnaces between the thirteenth and the seventeenth centuries. Iron ore deposits were often donated to them and the monasteries sold their surplus iron as well as the phosphate-rich slag from their furnaces, which was used as an agricultural fertilizer.
In 1709 Abraham Darby, a Quaker iron founder in Shropshire, England, used coke instead of charcoal to smelt iron ore in his improved blast furnace. He also processed cast iron into wrought iron and steel.
SEE ALSO: CONTROLLED FIRE, OVEN, BELLOWS, STEEL, WROUGHT IRON, ELECTRIC ARC FURNACE
- Blow Glass
It was the Syrians who first learned to blow molten glass through a hollow metal tube and shape it into intricate forms. Although the technique for producing glass had existed tor about two and a half millennia, it was only in approximately 100 B.C.E. that the hazardous art of glassblowing-using glass melting at a few thousand degrees Fahrenheit-was mastered.
Glassblowing is the process for forming glass into a desirable Shape, and this ability to form iconic, practical, and elegant shapes out of glass has been of incalculable value and practical benefit to society. Glassblowing machines have now largely replaced the Syrian specialists, but the science behind the technique remains the same. Molten glass is first introduced to the end of a hollow tube. A bubble of air is then blown through the tube, and as the bubble passes out of the tube a covering of molten glass forms around the sphere of air. This glass covered bubble, still attached to the tube, is either placed within a mold of the required form and enlarged through further blowing, or sculpted with tools into the desired shape.
The glass is then allowed to coo slowly to complete the process. It is the fact that glass has no set melting or freezing points that makes glassblowing possible; as the temperature rises or falls, the state of the glass gradually changes The rise of the Roman Empire at around the same time as the beginnings of glassblowing greatly facilitated the proliferation of the art. By adding manganese oxide to the mix, the Romans also discovered clear glass in around 100 C.E, which was used for architectural purposes.
SEE ALSO: GLASS, GLASS MIRROR, SPECTACLES, MICROSCOPE, ELESCOPE, CONTACT LENSES