How can you tell if a Purple Clay Teapot has been fired, and furthermore, determine the firing temperature? Is it really possible to judge the firing temperature of a purple clay Teapot from its sound?

When the rim of the lid (the male joint) fits snugly with the rim of the pot (the female joint), and you lift the pot, during this process:

If the sound produced is sharp and high-pitched, it indicates that the teapot was over-fired and has low breathability.

If the sound is dull and muffled, it suggests that the teapot was under-fired and has excessive breathability. If the sound is clear yet not shrill, with resonant echoes, it suggests that the teapot was properly fired and has appropriate breathability.

It's important to note that different types of clay will produce completely different sounds. When properly fired: red clay produces a sharp sound, conglomerate clay a harmonious sound, and purple clay a deep, steady sound. Comparisons should not be made between the sounds produced by different clays.

Judging the quality based on sound is not a scientific method, but it can reveal certain issues.

The sound being muffled or crisp mainly relates to the degree of vitrification (firing degree): A higher degree of vitrification results in a crisper sound, lower water absorption, and a lustrous appearance; a lower degree of vitrification results in a more muted sound, higher water absorption, and a dull appearance lacking luster.