First, the extinguisher valve is removed and the threads and interior of the cylinder are checked for corrosion, pitting, and any other abnormalities. [29 CFR 1910.157(f)(3)] If the cylinder passes the visual inspection, it is placed into a steel chamber, which is then filled with water at normal pressure.
Updated April 17, 2017. The earliest dated printed book known is the Diamond Sutra, printed in China in 868 CE. However, it is suspected that book printing may have occurred long before this date. In 1041, movable clay type was first invented in China.
Books printed on presses before the year 1501 are called incunabula, which comes from a word meaning cradle or birthplace in Latin. Although printing was certainly in its infancy prior to 1501, the actual printing process of using movable type on a wooden press did not change a great deal over the next 350 years.