It is not impossible to burn red bricks in ancient times, so why not use blue bricks instead of red bricks? Is there a reason for this? First, the use of blue bricks is related to the worship of black in Qin Dynasty. The Qin dynasty always liked black, soldiers' clothes were black, flags were black, and even the emperor's robes were black ... In this case, the solemnity of the building should reflect black. So it is not surprising that Qin Gong, Epang Palace and the Great Wall are all made of blue bricks.

Second, the use of blue bricks involves yin and yang and five elements. In the theory of Yin and Yang, cyan (black) is water and red is fire. Tao Te Ching says that goodness is like water, and water conservancy is used by all things. The ancients knew more about the relationship between the five elements and water. The building is made of blue bricks and the overall feeling is "blue". The main water, that is, fire, also shows virtue.

Third, the use of blue bricks is also a demand for technology, performance and aesthetics. The firing methods of red bricks and blue bricks are similar. Blue bricks only add a process, namely watering and cooling. Water cooling not only appears black, but also improves the quality of bricks. If the baked brick is glazed and returned to the furnace for the second time, it will become glazed tiles and glazed tiles.

Blue bricks are characterized by high density, no deformation, good frost resistance and no fading. Oxidation resistance, hydration, weathering and erosion. Pavilions and pavilions made of blue bricks, as well as private houses, especially Huizhou and Fujian schools in the south, Beijing and Shanxi schools and other residential buildings in the north. Bring exquisite, simple, calm and quiet beauty. As for the city walls preserved in Xi, Nanjing and other ancient cities, the Great Wall of Wan Li in Yanshan Mountains gives people a majestic, solemn and domineering feeling.