Slip, engobe, glaze and washes are terms you often hear when you delve into ceramic decoration. These terms have always been a source of confusion for me, especially since different ceramists give them different meanings. A clear definition can help to bring order in the chaos. But even more important is gaining insight.

You can memorize definitions, but I’m happy to leave that to AI models. More important is understanding both the differences and similarities between these materials for ceramic decoration. In my opinion, it is essential to recognize that all of these decorating techniques are part of a continuum.

This continuum extends from slip, through engobe and glaze, to washes. Based on the amount of clay (the source for Al₂O₃) and quartz (SiO₂) you can put this into perspective.

This is easy to visualize with the help of the “Stull graph”. R.T. Stull made this graphic in 1912 to classify glazes. But also very useful to gain insight into the entire ceramic decoration spectrum.