Formulation of ceramic engobes with recycled glass using mixture design

In this work glass frits were fully replaced by recycled glass in engobe compositions. Engobe is an interlayer between glaze and substrate in traditional ceramic tiles. Five ceramic raw materials were used to formulate engobes. Linear shrinkage, water absorption, whiteness, water stain and coefficient of thermal expansion were measured in designed mixtures and described by mathematical models. A statistical analysis enabled describing the engobe properties at a 95% confidence level. A major influence of the raw materials interaction on the engobe properties was determined as a result of the chemical reactions during firing. According to the response surface analysis performed, it was possible to find an area in the triaxial diagram where all properties were optimized.