Thixotropy
Thixotropy is a physical property of ceramic suspensions, such as slip, that describes how they become more liquid when agitated, mixed or subjected to mechanical forces, but regain their thick consistency when at rest. This property is especially important in slip casting, where the slip must flow easily to coat the inner surfaces of the molds but must remain thick enough to form a solid, uniform layer once poured. In addition, in the application of engobes and glazes, thixotropy ensures that coatings are evenly distributed without drips or unwanted buildup.
In practice, thixotropy is achieved by the addition of deflocculants or thickeners that adjust the viscosity of the material according to the working conditions. When the slip is subjected to agitation, external forces break the internal interactions between the particles, reducing the viscosity and allowing the liquid to flow freely. When agitation is stopped, these interactions are quickly restored, returning the slip to a thicker, more stable state that prevents particle settling and maintains an even distribution of the applied material.Interesting Fact
Thixotropy is also used in other industries, such as paints and cosmetics, to control the viscosity of products. For example, in thixotropic paints, viscosity decreases when force is applied with a brush, allowing for better coverage, and increases when resting, preventing the paint from spilling or dripping.Helpful Tip
Maintain the consistency of your slip at a suitable level by adjusting the thixotropy to prevent it from settling or thickening too much before use. This can be achieved by controlled addition of deflocculants or thickeners and by ensuring homogeneous mixing prior to application. Test small quantities to determine the optimum formulation to suit your specific casting and glazing needs.
