So, I sat down and had a good talk with myself, trying to figure out what exactly it was that I didn't like about these assignments. I came to the conclusion that I simply didn't feel challenged doing these really basic assignments so I set about trying to make them more challenging for myself. For the plate assignment, I decided to try making a plate that isn't a plate using the slip-dipping technique that I used for my class this summer. These engages my need to challenge preconceived notions of what objects should be by challenging the notion of a plate by creating one that certainly could not be used to eat dinner of off.
For the line blend glaze assignment I chose to try something a little more challenging. I have a teapot that I affectionately refer to as my studio teapot because it follows me around from one studio to another depending on where I am working. This teapot has a very unique "bubble" glaze to it that always draws the attention of my students. Many's the time that I have issued to challenge to a student when they admire the teapot. I tell them that if they make a teapot, I will figure out how to make the glaze. So far, no one has taken up my challenge, but I decided that the time had come for me to try and develop this glaze. Since a picture is worth a thousand words, see the images below for the story.
Magnesium carbonate has the chemical formula 4MgCO3.Mg(OH)2.4H2O. It is a very light material and the non-ceramist may be more familiar with it as its use as chalk used in gyms across the country. According to the Digital Fire website, magnesium carbonate does not give up its MgO molecules easily, making it a highly refractory material, which is why it causes glazes to become matte. Magnesium carbonate can also induce crawling because of the decreased amount of glaze melt coupled with the extremely small particle size which causes a high amount of shrinkage. Magnesium carbonate has a high loss on ignition which may cause issues with the surface of the glaze because of out gassing. Digital Fire recommends dolomite or talc as a better source for magnesium in a glaze, but for this type of crawling glaze it is perfect.
Once the amount of crawl had been established, I then took that mixture and added zinc oxide in increasing amounts up to 10%. These tests are currently being fired, but I will update this post once I get them out of the kiln.
Zinc oxide is most commonly known as the classic white line of sunscreen our mom's used to apply to our ears and noses as kids to keep us from burning. In glazes zinc oxide provides a ready source of flux, particularly in electric kilns. An addition of 5% zinc oxide to a mixture of kaolin, silica, feldspar, calcium carbonate, dolomite and talc will create a nice, glossy glaze, while small additions of zinc over 5% will further cause the mixture to melt. It is a key ingredient in crystalline glazes and is usually added in amounts of about 25% in these glazes. For the purpose of the glaze being developed, the zinc will provide additional fluxing to the mixture which should hopefully round off the edges of the bits of glaze.
In other news, I finished off the last of the houses for my commission tonight, much to my delight. Now I just need to box them up and take them over to the installation site. The installation has been postponed until November 19 so I will hopefully have images sometime around Thanksgiving.