Matt Katz Workshop 2025

by JUDY McCALLUM

Just prior to the 2025 Triennale, Wedge, 19 potters spent 4 days learning about glazes in the beautiful purpose-built Karlup studio in Alfred Cove. We were enrolled in Glaze of our Lives, Matt Katz’s introductory glaze course. There was a lot of nervous excitement in the studio. Matt initially came across as a big loud American, but we all discovered Matt to be a brilliant teacher with an engaging personality.

As Pam Thomson, one of the SORPC participants recalled, “For someone like me, Matt made chemistry easier to understand for the first time ever. His knowledge and way of teaching so much into a 4-day course was incredible.” She added, “I think we were all exhausted at the end.”

A majority of participants were potters from South of River Potters Club and Studio P with several potters coming from regional areas including as far away as Esperance. We were a diverse group with a thirst for glaze knowledge and had a range of levels of experience.

The course was a mix of talk, questions and answers, making glazes and firing test tiles. Initially Matt explained a few key concepts of glazes and glaze chemistry and concepts of firing. For example, he explained that a glaze is just a very thin coating of glass but because silica naturally melts at 1700 degrees celsius we need to add materials to support glaze structure (alumina) and fluxes to reduce melting temperature (alkali metals and alkaline earths). Matt reiterated, “The recipe doesn’t tell us what the glaze will do or the temperature of melting, but the chemistry will.”

In terms of firing he explained that heating induces chemical reactions to occur. As the course progressed he added more detail and explanation about raw materials, the periodic table, compensating for changing the materials in a glaze and firing.

Each participant was given a particular glaze recipe. Mine was Zinc Pinc and contained zinc oxide as an Alkaline Earth and Chrome oxide as colourant to give a dusty pink coloured glaze.

The next day we made up the same glaze but with changed amounts of kaolin (source of alumina) or silica (no kaolin, double kaolin, no silica, double silica) and Matt explained how to adjust the amount of other materials in the glaze to account for changes in kaolin and silica. The first day we made up our own glaze, carefully measuring out the materials for firing overnight.

We were all excited to see the results and how these changes had moved the glaze to different places on the Stull Chart. The ratio of alumina to silica will tell us what the glaze will do. For

example, take out the silica and the glaze becomes matte, whereas with too much silica the glaze doesn’t melt so is underfired.

On the third day we mixed up our glaze without colourant and added different colorants to separate containers: cobalt carbonate (0.5% & 2%), chrome oxide (0.5% & 2%), copper carbonate (1% & 4%), red iron oxide (3% & 9%), manganese dioxide (1% & 4%), rutile (3% & 9%) and to remaining containers stains of our choice or a mix of glazes.

This gave a great array of different colours and effects. It was a busy few days with a great deal of concentration required for listening, calculating, and measuring quantities. Over the lunch catered for each day we were able to chat with new friends and exchange learnings as well as work out new questions to ask. We all went away with a new confidence to further develop our knowledge and experiment to create different colours and effects.