But clay also has a property that has ruined many a piece: it shrinks when it dries out. And that shrinking process can sometimes lead to ugly cracks in your latest creation. But how does that actually come about?
What causes cracks in your clay?
The different parts of a piece usually do not dry at the same rate. Thin, small shapes dry faster than large, thick shapes. For example, you may have noticed that a cup handle dries faster than the cup itself.
This means that the parts of your piece also shrink at different rates. And that creates a certain tension in the clay. As long as the clay is still wet and workable, it can withstand that stress. But once the clay gets drier, cracking is the only way out.
Not all types of clay crack equally quickly. A clay with high plasticity has smaller clay particles, to which the water in the clay can bind better. When that water disappears during drying, it creates more space and thus more tension between the clay particles. This increases the risk of cracking.
Clay types with high moisture content, such as porcelain, also crack more quickly. This is because when they dry out they shrink very much in a short period of time. As a result, the clay has less time to withstand the stress.
High probability of cracking
Certain parts of your piece are more at risk of cracking than others. Handles, for example, as well as embellishments and fine details. These parts are not only thinner, and thus dry out faster anyway, they are also more exposed to the air than the rest of your piece.
If your piece has walls of uneven thickness, chances are you will get cracks. This is because the thicker parts dry slower than the thinner parts. This is also why the base of a bowl or cup is more at risk of cracking than the edge. Although this is not only due to the thickness of the clay, but also to the alignment of the clay particles.
By throwing clay, you in fact make sure that the clay particles are increasingly aligned in the same direction. But at the base of a bowl, that effect is not as strong. The clay particles remain more as they were: randomly aligned. As a result, the foot shrinks less quickly than the rest of the bowl, which does align evenly. And that can lead to cracks.
Finally, there is the moisture content in your clay. Clay straight out of the package can have a lot of unevenness in it. Certain spots are more moist than others. Once again, a recipe for cracking. Wedging well is key! And if you want tips on how to avoid those cracks, read on in this article.
