After the successful coprolite testing and firing I am now working on another research project. This time developing clay bodies and castable for kiln building for the Oxford Anagama Kiln Project . These are the second series of clay body tests, and what's interesting for me is how much can be learnt about a clay without recourse to expensive scientific approaches, such as chemical analysis and temperature expansion tests.
The bars are then wiped with a lightly damp sponge and weighed again.
The porosity of the clay can be calculated using the following formula:
soaked weight - dry weight/soaked weight - immersed weight x 100
Porcelain often has a very low porosity as it is fully vitrified, giving it translucency. However, over vitrification can be problematic for stoneware clays, and a porosity of between 2 and 4% is generally better.