Air bubble is the first microstructure we can find on the porcelain ware.  Depends on the procedure of production for example how the clay was treated, how dry the paste was, how think the glaze was, and how the firing environment was, the air bubbles could show with different sizes and different densities.  Here we show the bubbles from blue and white porcelain.

According to the size (mainly diameter) of the bubble, we put those bubbles the diameter <40 μm into small bubble group.  Those bubbles with diameter between 40 μm and 80 μm are in middle bubble group. The bubbles in the big bubble group are > 80μm.

Yuan

The air bubbles showed with quite very low density comparing to those from the later period. In the area of 1mm², there were less than 100 bubbles in number.

From the picture we would have an idea that most of the bubbles are with big size (>80 μm). But looking at the bubble diameter distribution graph, we can see that the bubbles concentrated around 25 μm.

Ming

The first glance, we can see that the bubbles are same sized. It is the bubbles from the sample of Chenghua period. Most of the bubbles are between 20 μm to 50 μm. However, a few big size bubbles appeared on the sample from Jiajing period.

Most of the bubbles concentrated around 25 μm on the sample of Chenghua period. While for Jiajing period, most of bubbles become smaller, which concentrated around 20 μm.

Qing

There were more than 200 bubbles in the area of 1 mm². Although a few big and middle size of bubbles showed the main bubbles were with small size.

The bubbles from Kangxi and Guangxu appeared quite similar. On both of these two samples, the bubbles concentrated around 20 μm.

Modern porcelain ware from 1990s

The bubbles seem more densely on the surface. They distributed as layers from the depth. These are different from the ancestors