Published Feb 21, 2022
I looooove a good old buttery matte glaze surface! Donna Polseno creates beautiful buttery matte surfaces with a lot of beautiful depth, but it took a lot of experimentation with cone 6 matte glaze recipes to get those surfaces just right. The glaze has to melt enough to move the glazes slightly and add depth to the imagery, but not too much!
In today’s post, Donna shares what she learned about getting that perfect melt, as well as a couple of her cone 6 matte glaze recipes. - Jennifer Poellot Harnetty, editor
My glazes are calcium-mattes that are fired in an electric kiln. The calcium is derived from wollastonite, a calcium silicate material, and from Gerstley borate, a calcium borate. I also have strontium carbonate as another matting agent in my glaze, which, like barium carbonate, enhances the colors. Wollastonite is known for forming minute calcium silicate crystals when cooling.
Many people down fire their kilns in order to slow the cooling rate to promote the formation of crystals, but I do not. My kiln is well insulated and therefore cools very slowly. Finding out that my kiln cooled slowly enough on its own to aid in the minute crystal formation was one of the lucky things I learned by chance in my goal to develop cone 6 matte glaze recipes with the richness and visual depth that is often associated with high-fire or reduction ware.
The things that I experimented with in that quest for visual richness and depth were, first of all, layering glazes on top of each other—not only trying one or two layers, but also discovering the different effects of certain glazes over others. Some combinations create a kind of micro-crystallization. My black cone 6 matte glaze recipe, for instance, makes nice specks of crystals over one of my base glazes and not the others because of the differing surface tension.
A second important part of the search was finding out how different stains and oxides completely change the melt of the same base glazes and how to use that to my advantage. Part of using stains and oxides successfully at mid range in an oxidation atmosphere is using several of them in the same glaze in order to achieve a more complex look rather than a more industrial out-of-the-jar look.
The third aspect to discover was the exact thickness of each glaze that would allow me to dip up to three layers of glazes. Due to the numbers of glazes I use in my process my glazes all need to be thin. I could not live without my hydrometer (check out this hydrometer DIY in the archives). I mix each glaze to a different specific gravity. The feel of the glaze can fool me sometimes and precision is crucial to my glazes success.
The fourth variable that took experimentation was the temperature. I have fired from cone 4 to cone 7, firmly settling on cone 5. I kept searching for the right amount of melt that would soften, yet maintain my complex decorative work.
Lastly, another factor that impacts the final appearance of my cone 6 matte glaze recipes is the fact that I choose a clay body that has a lot of ball clay and therefore is not overly white, as many people desire, but it gives a lot of the character to the overall look of the work.
Cone 6 Matte Glaze Recipes – The Perfect Melt
For me it is all about the perfect melt. The glaze has to melt and move my marks and therefore have a bit of mystery as well as depth. Initially, when I started this work, I had a regular electric kiln and relied on a visual cone to judge when the firing was complete. If the glaze melted the slightest bit more than I had determined was perfect, I was distraught. The designs were too mushy. If it was a shade less than desired, I was also distraught because the marks were too stiff. I now enjoy the precision of a computerized kiln with three thermocouples. My glazing method is complex with many mundane details, but my basic process is to dip the pieces in one glaze first. I then make my various lines and marks with fine Chinese brushes using liquid Forbes wax. I sometimes paint different shapes with liquid latex resist before dipping a second glaze. More wax is then painted or latex peeled off, before dipping a third glaze. My glazes are naturally hard in their dry state rather than powdery and this is very useful when using resists and multiple layers. With the perfect melt, the wax resist lines actually move in on themselves so that they look even more delicate than when I painted them. The right melt gives fluidness to the marks and a subtle translucency to the layers.
Try out my cone 6 matte glaze recipes and see if you like the results too!
Donna Polseno is an artist and educator who, along with her husband and fellow ceramic artist Richard Hensley, lives in Floyd, Virginia. See more of her work at www.donnapolseno.com.