Copyright 2008 Elizabeth Lurie
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EXPLORING COLOR
Like everyone else, I love color. Color can be very seductive and as a young potter, I learned that a fabulous color could not make up for a form that was ungainly or poorly articulated. In ceramic glazes, color comes from varying amounts and combinations of metallic oxides like iron,cobalt and copper. For many years, every kiln load has contained tests. One of these led to the development of my turquoise glaze. The first pieces I fired with that glaze almost ruined my kiln, but the color was so spectacular, I had to pursue a design that would use it to good effect. The same is true of my "eggyolk" glaze seen in the espresso cup, which sadly, I can no longer produce because the rutile that produces the color is no longer available.
I also developed a celadon type glaze that I call "Robin's egg" and a saturated red iron glaze, seen on the cup and saucer. Developing a glaze from "scratch" is a process which involves several phases of time consuming testing,not to mention fitting the design to the glaze. For ceramists who are reading this, I should say here that all of the colors you see were developed at cone 9 and 10 in an electric kiln , using combinations of metallic oxides for color. In the next few months, I will be trying some ceramic stains for the first time.
Below, you will see pictures of test tiles and test pieces that have been done over the past few years. It's one thing to produce a beautiful glaze on a test tile and another to use it successfully on a pot.
The first series of tests shown below are of a glaze recipie that I found in Greg Daley's excellent book, Glazes and Glazing Techniques.
Cup with turquoise glaze
Above, left,espresso cup and saucer,robin's egg and red iron glazes. Above,expresso cup and saucer, white matt and egg yolk glazes.
Glaze B (from Greg Daly)
Nepheline Syenite 30
Whiting 26
Silica 30
Kaolin(EPK) 14
The sample shown at the left consists of 88% of base B base plus 12 lithium and 1 copper carb. As you can see, it is clear and crazed with blushings of pale yellow.
Below: Two groups of test tiles showing variations of glaze B.
The top row from the left shows varying amounts of copper in the
first three tiles. The amount of base glaze in each sample varies and lithium was added to cause crazing and to make the color more vivid. The three on the right have iron for a pale honey and manganese for a warm brown.
The bottom row shows a stony matt created by using a smaller percentage of the baseand adding a large portion of alumina hydrate. This matt is slightly rough but not unpleasant to the touch. It has gray speckles throughout and is more gray where it is thick. Scroll down to see a small tea bowl glazed with the same glaze as the first tile in the first row.
The next group of test tiles involves a glaze recipie(282), that I have had for thirty years. I had used it briefly as a clear over white porcelain, but I did not like it's tendency to form crystals. I knew that it had a great color response to metallic oxides but I wasn't interested in exploring that then. Recently I tested 282 with the oxides shown in the tiles below. I expected to get a nice blue and maybe a nice honey color, but I was totally unprepared for the variety of results that I got.
This is also a clear glaze but with no crazing-very smooth and shiny. Scroll down to see a small cup glazed with 282 with additions of Iron Oxide and Chrome. The glaze flows enough to outline the texture in the side of the cup but not enough to run off the pot and the texture is very pleasant, smooth and almost waxy.
Porcelain teabowl glazed with Daly B with copper.
Small teabowl glazed with 282 containing 3 percent iron and 1 chrome.
Scroll down for more images
