Finding a Glaze… Part 1

Figure 9 - Layering Glazes

Love of Glaze

Wrapping pottery in patterns of color is both incredibly satisfying and very frustrating.  It takes real discipline to create a beautiful glaze for functional pottery. Even if the glaze itself only requires a few basic ingredients, the amount of variation in creating, applying, and firing the glaze is limitless.  A person could invest many lifetimes, and still never exhaust the depth of possible colors.  And once you fall in love with a glaze, it is a true test of your skill to reproduce the pattern time and time again. You need an intimate understanding of a glaze’s raw materials, the best way to apply the glaze, and a firing schedule that grows the crystal patterns you desire.


Understanding Materials

In my studio you will find hundreds, of glaze tests hanging on the wall (figures 1, 2, 3). Over the years I have explored thousands of glaze variations to make me a better potter. Early in my career I made the choice to mix my own glazes, consuming many of the famous glaze recipes passed down over countless generations.  These days I primarily focus on glazes tested and defined by John Hesselberth and Ron Roy, in their book Mastering Cone 6 Glazes (note: the paperback version is out of print $$$ but there is an ebook version available).  In their book, John and Roy put an emphasis on testing glazes to ensure they are not only beautiful, but also safe with food.  But just like any recipe, the opportunity to express your own creativity is endless.

In my own tests, I usually start by selecting a few base glazes from John and Ron’s book.  For example, I might select their High Calcium Semimatte Base 1, the Zinc Semimatte/Glossy Base, and a Glossy Base (figure 4).  With each base glaze, I then make incremental changes to the amount of a specific colorant.  In the example (figure 5) I add 1.0%, 3.25%, 5.0%, 7.5%, and 10% of Rutile (a glaze colorant) to a Glossy Base glaze.  See how different the color can shift from a cool blue mist to a warm orange.



Of course once you understand your basic materials, you will quickly find that your methods of application can have a huge impact on the final color.  Going back to our Rutile example, first samples are usually created by brushing on the glaze (figure 6).  Brushing, pouring, or dipping can introduce a lot of variation, especially compared to spraying glaze onto pottery (figure 7).  But the important thing is to explore and find out for yourself how small changes can have a big impact.  I find it is also important to see how a glaze stands up to gravity (figure 8).  Certain glaze materials can have a strong effect on how easily a glaze flows off the the pot, so I always test samples before using the glaze on a large area.  And finally, once I select basic glaze recipes that meet my technical needs, then the fun really just begins.  I create hundreds of samples to explore the impact of layer different glazes (figure 9).  I am always amazed at the depth of color that can be achieved by mixing glazes.


Part 2 of this post will focus on reproducing results.