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Found 4 results

  1. Mullins Pottery

    Local clay scumming

    Hi all, I've posted about this local clay body before and I'm checking with the forum to get ideas on trouble shooting another issue. I'm firing to cone 05/04. The body itself is a beautiful lowfire body but after the bisque it gets a white scum on the surface . I'm not sure what it is that's causing the whiting but I think that the clay body would be gallery quality were it not for this blemish. I have sanded the surface after firing and the white can be removed. Obviously this is not a solution but it confirms that there is a beautiful clay body just below the surface. Any ideas of how I can resolve this kind of issue in the clay refining stage? I have links for some images below https://drive.google.com/file/d/0BwDDXHDlS0HGMHVKZVE1VDJuNkUzY2JIbXFFZ2NwMWJ6RHR3/view?usp=sharing https://drive.google.com/file/d/0BwDDXHDlS0HGa2Q1LXFkMy1sLVlMaGJBdkE3djN5RUtxNnhJ/view?usp=sharing https://drive.google.com/file/d/0BwDDXHDlS0HGMjZQZ1kzb1JnQklZbzc1WExhM1Q2VWVUVjFz/view?usp=sharing https://drive.google.com/file/d/0BwDDXHDlS0HGSjFXa2MycWRLcVZwVlJPNWxMM0VYTjlwQ0tn/view?usp=sharing
  2. Mullins Pottery

    Clay processing

    Hello all, As is happens I live in a desert. All the local earthenware clay I dig up is already dry and mostly free of impurities. Much of the research I've done regarding the processing of clay suggests that after drying the clay one should break up the dry bits into pieces then screen dry then re-hydrate to appropriate consistency. In my process I basically use the blunging process instead of dry screening. Aside from the drying process taking a couple days I cant think of anything that makes this process less viable. I've found this to be quite effective in weeding out the impurities. I'm wondering if there's anything wrong with doing a wet screening as opposed to a dry screening. Any thoughts? My process is this: 1. Dig up clay 2. Re-hydrate clay 3. Blunge into slurry 4. Pour through screen mesh twice 5. Dry to appropriate consistency on drying table 6. Wedge into logs 8. Bag & age
  3. Hello! I have been harvesting a beautiful blue marbled clay, processing it, and then making cups. I did a test-bisque at cone 04 which turned out great, but the low-fire glaze that I applied afterward (cone 05-06 glaze) did not absorb easily and took several hours to dry. Is it worth trying to fire it anyways? And in the future: Will I run into complications if I bisque at a lower temperature (cone 05-08?) then apply glaze and fire at 05? The glaze directions say to bisque at cone 04, but I'm assuming its not necessary if the clay I'm working with is extremely low-fire? Thanks for the help! I am a beginner ceramicist working at home with access to a community kiln. I have never worked with locally harvested clay before and its amazing but difficult to figure it all out.
  4. Apologies for the lengthy post, but i'm hoping providing lots of detail will increase my chance that someone will here will have the missing piece to my puzzle... I have been working off & on for nearly a year, trying to come up with a workable ^6 body from locally dug clay of uncertain composition. This clay comes from the ground gray, and fires to beige/buff color at ^6. Tested first at low (^05-^06) fire. After second firing w/ low-fire glaze, test-tiles were like shortbread cookies. Very dry & easily broken, and the glaze looked like all of the water had baked out of it, leaving behind a layer of dry ingredients - much like you would see if you put a thin layer of slip on a block of wood and let it dry. Test fire at ^6 was a better - but still very porous (20+% absorption). Glaze soaked into clay like a sponge - came out looking like it had been painted with water-colors. Early tests had lots of lime-pop, so watered raw (dug) clay to thin slip consistency and poured through 80 mesh screen after reading the lime particles smaller than 70 mesh are usually not a problem. Apparently this is true, as I've had no more lime-pops. Have now tried over 3-dozen different variations, most of them with 50% - 75% 'raw' clay, and the balance made up of different combinations of OM4, EPK, Flint, Potash Spar, and Goldart. For each test, I make a small batch of clay, roll it into a slab, and cut into 2cm x 10cm strips, which I drape over a plastic tube to form an arch. I bisque fire both strips, then glaze one and fire the other unglazed - at ^6. Several have looked promising at the bisque stage, and actually came through the second firing in good shape unglazed -with around 4% absorbancy... But I'm having lots of confusing results with the glazed pieces. I've tested all of the mixes with the same two glazes - Randy's Red, and a Tan - dipping each end of the test strip into one glaze, so there's a small overlap at the middle. Both glazes are mixed by the potter that owns the studio. Her RR recipe is the same as found on digital-fire, minus the bentonite. (Unfortunately, she's never worked with anything other than commercial clays, and knows very little about clay-body formulation.) Here's where the frustration begins: Several pieces have come out of the glaze test looking great on the tan end - but with the RR end ranging from dull to lava-like (very porous). With several tests, the RR end has deformed severely, while the tan end held it's original shape. The photo below is a test with 75% 'raw' clay and 25% EPK. Both pieces were the same shape & size after bisque firing, and were fired together on the same shelf at ^6. The unglazed piece retained its shape, but the glazed one sagged heavily on the RR end, while holding shape on the tan end. (The unglazed piece in the pic is wet, as I started soaking for absorption test before taking the pic, so color looks a little darker than it really is.) I know different glazes react/interact differently with different clay bodies - but have not found any info that suggests why there would be such a drastic difference between glazed and unglazed pieces fired together. **Edit: Got my pic's mixed up. The sample in this pic is 65% local, 25% EPK, 10% OM4.
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