Clay is more absorbent than porcelain. This is due to the differences in their compositions and structures. Clay is a natural material composed of fine particles, which allows it to absorb liquids more readily. Porcelain, on the other hand, is a ceramic material that is fired at high temperatures, resulting in a dense and non-porous structure.

The absorbency of a material is influenced by its porosity, which refers to the presence of tiny spaces or pores within the material. Clay has a higher porosity compared to porcelain, which means it has more pores that can hold liquids. This is evident in the way clay pots and dishes are traditionally used for brewing tea or storing liquids, as they can absorb some of the liquid, which can enhance the flavor or preserve the contents.

According to a study published in the Journal of the American Ceramic Society, the porosity of clay can range from 0.1 to 0.5 millimeters, while porcelain typically has a porosity of less than 0.1 millimeters. This significant difference in porosity directly correlates to the absorbency of the materials.

In practical terms, the absorbency of clay is further enhanced by the firing process. When clay is fired, the water within the clay evaporates, leaving behind a network of interconnected pores. These pores are what allow clay to absorb liquids. In contrast, porcelain is fired at such high temperatures that the clay particles bond tightly together, filling in any pores and creating a non-porous surface.

In conclusion, clay is more absorbent than porcelain due to its higher porosity and the presence of interconnected pores resulting from the firing process. This inherent characteristic of clay makes it suitable for applications where absorption is desirable, such as in pottery and ceramics.