Plasticity
Plasticity is a fundamental property of clay that determines its ability to be molded and maintain the shape imparted without cracking or breaking. This characteristic is essential in ceramics, as it directly influences the ease with which various shaping techniques, both manual and mechanical, such as throwing, hand shaping, pressing and molding, can be performed. A clay with high plasticity is more flexible and adaptable, allowing complex and detailed shapes to be created with greater precision and less risk of structural defects.
The plasticity of a clay depends on several factors, including the water content, the size and shape of the clay particles, and the presence of additional minerals or additives. For example, ball clays, with fine, well-distributed particles, tend to be highly plastic, making them ideal for techniques that require detailed modeling. However, this high plasticity can increase the risk of shrinkage and cracking during drying and firing, so they are often mixed with degreasers such as grog to improve their thermal behavior and reduce shrinkage.
In addition, plasticity can be modified by kneading and malting the clay, processes that redistribute the water content and clay particles, eliminating air bubbles and improving the homogeneity of the mixture. The addition of additives, such as starches or natural gums, can also increase plasticity, allowing greater fluidity in the molding and better adherence between the different parts of a ceramic piece.Interesting Fact
In ancient Mesopotamia, empirical methods were developed to evaluate the plasticity of clay, using the sound it emitted when handled. If the clay produced a soft "crackling" sound when worked, it was considered to have the ideal consistency and plasticity for modeling. This practical knowledge made it possible to select and prepare clays suitable for different types of pieces, optimizing efficiency and quality in ceramic production.Helpful Tip
To improve the plasticity of a clay that seems too stiff, you can add water gradually or mix it with high plasticity clay, such as ball clay. Kneading the clay properly is key to evenly distributing the water and eliminating air bubbles, which improves its plasticity and workability. Also, consider using additives such as grog or guar gum, which can increase the clay's flexibility and adhesion, facilitating modeling and reducing the risk of cracking during drying and firing.
