|Monthly Tech-Tip |
This shows the soluble salts in the material and the characteristic cracking pattern of a DFAC test disk when made from a low plasticity clay. Notice the edges have peeled badly during cutting, this is characteristic of very low plasticity clays.
Plasticity (in ceramics) is a property exhibited by soft clay. Force exerted effects a change in shape and the clay exhibits no tendency to return to the old shape. Elasticity is the opposite.
The DFAC Drying Factor test visually displays a plastic clay's response to very uneven drying. The test is extreme enough that almost all plastic clays will crack.