Sunday, September 25, 2011

Closing in on Duckshead

The saga continues. Duckshead remains elusive, but a battery of tests has provided about the best leads to date. I started with the Moss Agate formula as a base. It is the glossiest, glassiest of the glazes and flows nicely. This is particularly important because it has to flow well when combined with the Turquoise glaze to make the most popular pattern of Duckshead and Turquoise. The Turquoise has been undergoing some of its own improvements over the summer as well so that it can be more glassy. So far so good.

The next step in finding a Duckshead has been to figure out what combination of metallic oxides will create black with the silver sheen that characterizes this unique glaze. Black is not at all difficult to get all by itself. I have created several of them int he last few months. But that metallic sheen is another story. It's subtle, providing a silvery look while remaining shiny. Many black metallic glazes tend to take on a "gun metal" appearance. That's pretty in itself, but the dull surface can often mean that the glaze is soft and will easily leach some of the oxides that give it its color. Leaching may not be dangerous, but the pottery will lose its luster and shine quickly.

And some of those oxides can, in fact, be dangerous if too much leaches.

So the secret is to get enough to do the job without overloading. That is what has been taking so long. The base glaze is now in place, and the process of coloring has begun. Recently, I created to triaxial blend sets - one composed of iron, copper and cobalt oxide and the other of manganese, copper and cobalt. These were blended in a series of combinations and the results were studies by both me and Sheila Varnum.

Here is a picture of the iron-based triaxial series

And here is the manganese series

They all look pretty similar in these photos, but believe me, there are marked differences. In the end, we chose one from the second series. It is the second from the left in the first row. This one has a beautiful metallic sheen and, with some adjustments to the other oxides, should make a beautiful Duckshead.

Of course, I've said stuff like this before. There are other issues to consider. The glaze must not only look nice in a dip test. It has to suspend well in water and apply well. Application has been the downfall of several attempts over the summer, but I have great hope for this one given that its base formula is already well tested. Earlier tests of a similar Duckshead test were very nice. Just not quite the color we wanted.

The test will be in the fire this week. If it looks good and passes the various tests for durability, you will find it out here.

And I will be VERY busy glazing until the snow falls.

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