How were the blue bricks made in history?

Ancient blue bricks were very strict with soil quality: firstly, the soil layer more than one meter thick on the surface of the soil field was removed, and the red clay below was selected.

"If you dig more than two feet to make ceramic tiles with clay, choose a sand-free clay foundation." Choose high-quality clay, cool and mix it, remove violence and increase flexibility, so it is "three days and two summers".

Soil that has been left for two or three years needs to be re-screened, mixed with neutral water and mud, refined and beaten.

The picture shows the workers turning the soil into mud to prepare for the next process.

The next step is blank making. There are two workers in one group, one is responsible for transporting mud and the other is responsible for billet. Two people can make about 350 yuan a day.

Extended data

There is an ancient brick kiln in Chuanzhen, Renqiu City, Hebei Province. The ancient brick factory built on this basis has always followed the traditional manual brick-making process. Each blue brick has to go through more than a dozen processes, such as earth borrowing, drying, blank making, kiln loading, firing and kiln discharging.

The finished product is blue and antique, and has been used in the renovation projects of ancient buildings such as the Forbidden City, the Temple of Heaven and the Summer Palace.

20 12 ancient building blue brick technology was selected into the provincial intangible cultural heritage list of Hebei province.

The technological process of making blue bricks is all manual operation, including selecting high-quality clay, drying in the sun, stirring, removing violence and softening, making it "three days and two summers", then screening, refining mud with neutral water and mud, making it into a blank, drying it in the shade, and finally firing it in a cellar at high temperature for one month.

This craft has been listed in the protection list of intangible cultural heritage in Hebei Province.