I'm currently using two types of clay body, low-fire: white clay and terra cotta
earthenware clay. I like the variety of commercially available glazes in
this firing range, and the 'forgiving' nature of the clay itself. By
forgiving, I mean that when I bend a piece of the clay and then flatten
it out again, it won't warp to the bent shape later while drying or
during firing like a porcelain body would be more prone to do. I'd like
to go to mid range temperature stoneware by year's end, but I'm enjoying
the lower fuel costs in the meantime while I learn how to use the
different tools and techniques. I would also love to eventually work
with porcelain, nothing compares to it's beauty, but I don't feel I'm
ready for the high temp firings just yet. I've read that porcelain is
for the more experienced hand. I'm not making functional ware (eating
utensils, teapots, or flower vases for example) or tiles/jewelry that
will be continually wet, so I'm not highly concerned with the piece
being vitreous; I glaze the entire surface so as to maximize resistance
to moisture. I use Laguna's #10-T white clay, and their #20 red earthenware (these are Northeast clays). The note in the supply list of the next post, about rolling out mid to high fire glazes shows why I haven’t yet started firing clay in the upper cone ranges, plus a few other reasons like I’m just starting out. When making a flat ceramic piece for tile or flat jewelry, keeping the raw clay slab flat at all times is more important in those higher cone range clay bodies, though I've heard that stoneware or a mix of stoneware/porcelain properties is easier to work with than a purer porcelain body. Stoneware and porcelain bodies are denser, and so have more ‘memory’. The increased number of platelets in the clay remember every shape you bend them into, and will try again at all stages of drying and firing to re-bend to those shapes.
That density of platelets, there because of the chosen formula of materials used in mixing the clay body, is also what makes stoneware and porcelain ware able to sustain higher temperature firings to become vitreous/glasslike, very strong and impervious to liquid. I can fire a low fire clay to it’s near-vitreous state, and the fired piece will have a ‘ring’, but the finished piece will be quite brittle and fragile in comparison to stoneware or porcelain clay bodies at higher cone temperatures. Also, bringing a clay to its near melting point in order to achieve a vitreous clay is not the main quality I'm looking for right now. Like I said I’m not making outdoor sculpture (water will get in and at freezing temperatures crack the piece), tile that will be in continuous contact with water like bath surround tiles, or with food and hot liquids like eating/drinking utensils, or functional flower vases; for now I’m making tiles to hang on an inside wall as is or in a group, or to use as coasters. The ones I don’t like can be broken for mosaics.
I glaze the entire piece except the hole on jewelry pieces, and over the top and a bit over the edge for tiles. That helps to create more of a barrier between moisture and the fired clay, but still shouldn’t be exposed to continuous water for a long time or water seepage is more likely to grow within the clay structure and out through the glaze over time. Those cracks in the glaze allow a healthy environment for bacteria to live in the fired clay, so cracked glazes are ok on non-functional higher fire clay bodies that were fired to their higher cone rating, but not so great on low fire clay bodies that haven’t been fired to their highest cone rating. At the lower end of their cone ratings, low fire clay bodies are still considered ‘open’, porous/punky, even after bisque and glaze firings when not brought to their upper cone rating. You can feel it in the weight, they feel almost as light as air (because they’re holding a lot of air!) Still, the pieces that I make will be around for a really long time…pottery shards of unglazed earthenware are thousands, sometimes tens of thousands of years old in the right conditions. That’s a lot longer than I expect to be around to see it deteriorate, and that's if I’ve glazed them well. So glazed low fire white clay and red earthenware is right for my application.
I’ll try and mention what I can now and then about the upper firing ranges (cones 5-8 for mid and cones 8-11 for high fire, approximately), but until I’ve experimented myself with them I probably won’t have much to add. That’s one of the main reasons I started this blog anyways, to organize my links to studio/production potters/artists and other pros within the industry who have many more answers than I do, the ones that I look to when I need answers, and there are a billion questions. I’m a lifelong learner so I don’t mind spending the time reading, practicing and experimenting; I’m in it for the long haul because of the clay itself and the way it makes me feel when I’m being creative with it. It’s something to look forward to, every day, and helping me to live in the present moment and appreciate life here on our beautiful planet and the gifts that it has bestowed upon all of us.
I use commercially prepared glazes and underglazes because at the scale I'm working at it doesn't make much sense for me to make my own yet. A two ounce jar of underglaze can cover a lot of pendants and tile! Plus there are tons of colors and textures available from several companies. Here are their color charts: Duncan, Amaco, Spectrum, Mayco and Laguna have underglazes and both low fire and mid fire range glazes, and Coyote has underglazes and mid fire glazes (cone 6). I'll be adding a list of great ceramic suppliers in the coming posts.
I'm reading all that I can on glaze chemistry at the moment, so who knows? It's yet another of my goals to someday mix and test my own batches. Be here for that, too, those first tests ought to be ...'interesting' shall we say. I'm using about a half dozen or so Duncan Envision transparent glazes and a handful of Amaco underglazes, both the LUG and Velvets series. I use the clear transparent LG-10 Amaco glaze over the underglazes. Both Duncan and Amaco have shown to be excellent product lines that 'fit' my clay body really well. My kiln is an Olympic Doll Kiln, just the right size for jewelry components and small (less than 4") tile. I dream of a gas kiln someday, don't we all, but I figure at the rate I make things now it would probably take me the better part of the year to fill more than a couple cubic feet of kiln space (mine is less than .5 cubic foot).
Here's a pic from my 2nd glaze firing:
Bad lighting... maybe I should leave pictures to my photographer daughter. I'll be going over all of the techniques you
see here in the coming months: stamp making, sgraffito, patinas...and I
have a bunch more that I'll be trying out for the first time including
slip trailing, paper resist, wax resist & cuerda seca, terra
sigillata, I have a long bucket list of things I *neeeeed* to try with
clay. I'll start from the beginning with slab rolling and work from
there. So take a trip to your ceramic supply store and pick up some clay
for goodness sake, you know this is what you want to do with your life!
That density of platelets, there because of the chosen formula of materials used in mixing the clay body, is also what makes stoneware and porcelain ware able to sustain higher temperature firings to become vitreous/glasslike, very strong and impervious to liquid. I can fire a low fire clay to it’s near-vitreous state, and the fired piece will have a ‘ring’, but the finished piece will be quite brittle and fragile in comparison to stoneware or porcelain clay bodies at higher cone temperatures. Also, bringing a clay to its near melting point in order to achieve a vitreous clay is not the main quality I'm looking for right now. Like I said I’m not making outdoor sculpture (water will get in and at freezing temperatures crack the piece), tile that will be in continuous contact with water like bath surround tiles, or with food and hot liquids like eating/drinking utensils, or functional flower vases; for now I’m making tiles to hang on an inside wall as is or in a group, or to use as coasters. The ones I don’t like can be broken for mosaics.
I glaze the entire piece except the hole on jewelry pieces, and over the top and a bit over the edge for tiles. That helps to create more of a barrier between moisture and the fired clay, but still shouldn’t be exposed to continuous water for a long time or water seepage is more likely to grow within the clay structure and out through the glaze over time. Those cracks in the glaze allow a healthy environment for bacteria to live in the fired clay, so cracked glazes are ok on non-functional higher fire clay bodies that were fired to their higher cone rating, but not so great on low fire clay bodies that haven’t been fired to their highest cone rating. At the lower end of their cone ratings, low fire clay bodies are still considered ‘open’, porous/punky, even after bisque and glaze firings when not brought to their upper cone rating. You can feel it in the weight, they feel almost as light as air (because they’re holding a lot of air!) Still, the pieces that I make will be around for a really long time…pottery shards of unglazed earthenware are thousands, sometimes tens of thousands of years old in the right conditions. That’s a lot longer than I expect to be around to see it deteriorate, and that's if I’ve glazed them well. So glazed low fire white clay and red earthenware is right for my application.
I’ll try and mention what I can now and then about the upper firing ranges (cones 5-8 for mid and cones 8-11 for high fire, approximately), but until I’ve experimented myself with them I probably won’t have much to add. That’s one of the main reasons I started this blog anyways, to organize my links to studio/production potters/artists and other pros within the industry who have many more answers than I do, the ones that I look to when I need answers, and there are a billion questions. I’m a lifelong learner so I don’t mind spending the time reading, practicing and experimenting; I’m in it for the long haul because of the clay itself and the way it makes me feel when I’m being creative with it. It’s something to look forward to, every day, and helping me to live in the present moment and appreciate life here on our beautiful planet and the gifts that it has bestowed upon all of us.
I use commercially prepared glazes and underglazes because at the scale I'm working at it doesn't make much sense for me to make my own yet. A two ounce jar of underglaze can cover a lot of pendants and tile! Plus there are tons of colors and textures available from several companies. Here are their color charts: Duncan, Amaco, Spectrum, Mayco and Laguna have underglazes and both low fire and mid fire range glazes, and Coyote has underglazes and mid fire glazes (cone 6). I'll be adding a list of great ceramic suppliers in the coming posts.
I'm reading all that I can on glaze chemistry at the moment, so who knows? It's yet another of my goals to someday mix and test my own batches. Be here for that, too, those first tests ought to be ...'interesting' shall we say. I'm using about a half dozen or so Duncan Envision transparent glazes and a handful of Amaco underglazes, both the LUG and Velvets series. I use the clear transparent LG-10 Amaco glaze over the underglazes. Both Duncan and Amaco have shown to be excellent product lines that 'fit' my clay body really well. My kiln is an Olympic Doll Kiln, just the right size for jewelry components and small (less than 4") tile. I dream of a gas kiln someday, don't we all, but I figure at the rate I make things now it would probably take me the better part of the year to fill more than a couple cubic feet of kiln space (mine is less than .5 cubic foot).
Here's a pic from my 2nd glaze firing:
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