» Electric Kiln Success: How to Get Exciting Ceramic Surfaces with Cone 6 Glazes

June 18, 2008

Electric Kiln Success: How to Get Exciting Ceramic Surfaces with Cone 6 Glazes

Denver, Colorado, ceramic artist Jonathan Kaplan is usually less-than-enthused by the results of using a single glaze in a Cone 6 oxidation firing. He reminds us that rules are meant to be broken in ceramics and it is important to always keep experimenting to get the results that excite you. Resist the habit of doing the same ol’ same ol’! Jonathan has developed some methods with which he tweaks his glazes and his firing schedule to add some oomph to his ceramic surfaces.

Today he shares his techniques for enlivening Cone 6 glazes and some of his favorite Cone 6 ceramic glaze recipes. - Jennifer Harnetty, editor.

Cone 6 Glazes

Color and texture in cone 6 glazes are the result of three variables: First, selecting proper glazes; second, learning how to layer and combine different glazes by pouring, dipping and spraying; and third, using a controlled cooling cycle to further enhance the color and texture. This slow cooling not only creates a visual dialog in thick and thin areas of glaze application, but also helps with the crystallization of certain materials, which adds depth and interest to the glaze.

This detail of the piece above shows the cooling crystals that developed during a controlled, slow cooling.

Glaze Application
I spray or dip glazes over each other. My experience is that no single glaze can provide a visually interesting surface in an electric kiln, although there may certainly be exceptions. My layering technique allows the many differing glaze materials to combine and melt in unique ways, providing a visually interesting surface with depth. All of this is caused by the interactions of multiple materials applied over each other. Applying glazes over textures in the clay allows the melted glaze to pool. A thicker concentration of glaze materials in these areas yields different areas of color.

When mixing and testing glazes for future use on your pottery, it is useful to try different methods of combining glazes. For example, if you mix up a few small test batches of different glazes, try dipping one glaze over the other on the top rim of your test tile. Then reverse the order. For instance, if you dip glaze A over glaze B, then do another tile with glaze B dipped over glaze A.

This article is included in Electric Kiln Firing Techniques and Tips: Inspiration, Instruction and Glaze Recipes for Electric Ceramic Kilns, which is free to Ceramic Arts Daily subscribers.

Firing
Most glazes have a range of several pyrometric cones. I fire my cone 6 glazes to cone 7 using a programmable controller with the following heating and cooling cycle:

1st segment - 50°F/hour to 220°F

2nd segment - 250°F/hour to 2167°F

3rd segment - 150°F/hour to 1500°F

I have found that this provides a better melt and allows a good mingling of the many layers of glaze. It’s necessary to experiment and test your glazes to determine their range. Kiln wash or stilts under your ware is a necessity!

It is fine to program a “hold” into the end of the second segment if you have a single zone kiln and wish to try to even out the firing from top to bottom. With the introduction of multiple zone controls on many of the new kilns, a soak at the end is not really necessary. If you don’t have a computer-controlled kiln, use the infinite switches to “fire down” the kiln. With the addition of a pyrometer and a decent thermocouple, you can achieve a reasonable controlled cooling cycle.

Record Keeping
It’s important to keep accurate records so when you get results that are pleasing, you can repeat them. In an electric kiln, repeatable results are easier to achieve than in a fuel-burning kiln, especially if your electric kiln is equipped with a programmable controller. There is no substitute for experimenting. It takes time and persistence to achieve the surfaces that are pleasing to you. No one glaze or method will work. It is a combination of glazes and applications, followed by the proper firing with a controlled cooling cycle

Recipes Remember to always test new glazes before committing them to your finished work!


Jonathan Kaplan has been working in ceramics for more than 30 years as an artist, potter, ceramic designer and educator. He currently resides in Denver, Colorado, and curates Plinth Gallery. See www.jonathankaplanceramics.com and www.plinthgallery.com.