When the raw materials are the same, the color of the finished product is mainly determined by the atmosphere in the kiln.
The firing method of Jianshui purple pottery is not mysterious. Friends who have a little knowledge of Jianshui purple pottery all know that: the oxidation firing is ochre red, the strong reduction firing is black, and the weak reduction firing is between ochre red and black, and the mixed atmosphere firing shows various kiln discoloration.
No matter what kind of firing atmosphere, the surface of the finished product will form a layer of fire skin with a thickness of about 1 mm. Finally, when grinding, you can see the real body of purple pottery by grinding off the fire skin.
In a strong reducing atmosphere, the purple pottery is black, but the surface of the fire skin is close to silver gray. When grinding, generally only the external surface is polished, and the interior of the pot will not be polished. On the one hand, they don’t deliberately look at the interior; on the other hand, internal grinding is very difficult to operate.
The fire skin is both inside and outside, so the friend asked, “why is the black inside and outside of the purple pottery pot different?” it should be that he bought a purple pottery pot fired in a strong reducing atmosphere. The outer part was polished to produce a pure black real purple pottery body, and the inner part was still the original fire skin.