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Genboomxer

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    Thousand Oaks, CA
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    Pottery, brewing, gardening, cooking.

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  1. This soil is from the west San Fernando Valley in So CA. What can I infer from the result I go? No bloating or black coring evident in the samples. I'm guessing I will need to stick to low-fire, majolica or non-functional projects? Thanks again for the knowledge.
  2. Hello again Nerd! I finally got around to firing a sample of my project to ^6. In the attached photo I have 2 samples. Top sample is native soil (I call it CPM) mixed 50/50 with ^10 b-mix. I'm pleased with the results so far regarding texture and color. Shrinkage is ~12%. I also glazed a small mug made of the same 50/50 clay body with a home-mixed celadon (Britt Basic) and it turned out quite nice. I does appear to have crazed though. The bottom sample is the native by itself fired to ^6. Dark brown and glassy. It broke during firing. Probably during cool-down? It isn't brittle as I've tried to break it by hand and it's quite strong. I think this answers the iron / pyrite content question? Thanks again for your insights!
  3. Thank you for sharing! The more I see of NC the more I understand why it is such a hub for potters. Three different varieties of clay within a stone's throw? Amazing. And their work is elegant. P.S. I took a look at your website and I really like your work. I especially like the Distress Cetre mugs, and the motivation and humanity that inspired them.
  4. Thank you! I started this project about 5 months ago, but I've only recently had the time and means to fire and test at home.
  5. Thank you for the links! I looked for similar topics here but sometimes if you don't use the right key word it doesn't come up. I did drop a piece of the fired clay into vinegar and it only fizzed for a second, so I'm interpreting that to mean I'm good on lime distribution. I am working on more test tiles today, and buying more witness cones for the varying temps I plan to test at. I think analysis will also help in that I should be focusing on practicing with what I have rather than playing with a theory. But I love learning new things. So much appreciation for the wisdom and guidance!
  6. Testing makes a lot of sense. Do you have a suggested lab?
  7. I guess I'm not sure what you mean by "what type of clay it is". I'm guessing it's a type of high iron, terra cotta earthenware. The soil is from the west San Fernando Valley of Los Angeles, in the shadow of the sandstone bluffs where I grew up. I know the S. F. Mission made its roof and floor tiles, as well as some tableware and storage ware from locally sourced clay, so this keeps me hopeful it is viable with the right treatment. I assumed I would have to do extensive testing because I haven't found a lot of other folks doing it online, and I have a tendency to do weird things few people do for my own creatively nutty reasons. Commercially available clay is great, but I want to add a personal, unique twist to my work if I can. I wasn't sure I would get this far, so I'm excited to do the work. I purchased some ball clay (OM-4) and feldspars for mixing my own glazes (another new experience of experimentation) so I will start to play with those ingredients and see where I get. It would help to have a methodology for adding such materials in the right ratios. It's not a deal breaker if I can't make a stoneware out of it, but I do want a durable and versatile local clay body for functional wares. A ball mill is not a budget priority so I will just have to work around it. Although I have a desire to see if the nearby sandstone can be used as a glaze ingredient. I did find a report on the sandstone. It is composed of 54% granite; 45% feldspar, cemented with limonite (iron ore). So who knows I might eventually get a ball mill (maybe a large rock tumbler? ) for that and see what happens. I've been trying to decipher the survey maps myself. I've read several, but they're pretty general for the area; no actual analysis of the specific soil, just suitability for farming and erosion characteristics. "Sandy loam" is not helpful. Mineral content of the soil is still eluding me, but I hunt on. Edit: P.S. - Any insights regarding the 50/50 blend with ^10 B-Mix? Does this theoretically up the maturation temp? I have only found one other person who has done this, and fired it to ^6 with success, but they haven't done any more than that. Thanks, Dave
  8. Thanks for the link! Turns out I've done most of what is suggested. I will do vinegar eat tonight because I know there was a lime industry uphill from my source and this is part of the geological makeup of the region. I have found more information about the source material (sandstone) than I have on the actual soil. Any help for where to look for that is appreciated. I tested a bar of it and broke it in half. No carbon coring at all. I do not have a small test kiln per se, but I do have 2 kilns to work with, one ^6 electric. 3.3 cu ft, and an ancient 7 cu ft gas kiln that can easily handle up to ^12, so I'm set there. I am in the process of testing, but I'm really new to this and want to make sure I get all the info I can. Also, if someone has already gone down the same paths I'm on, maybe I don't have to do as much work. I want to explore all the possibilities with this wild clay. What can I do with earthenware? How can I make it a clay body that matures at ^6 and/or ^10? All the stuff. Thanks, Dave
  9. Hello Forum Folks, One of the current projects I'm working on, now that I've acquired a little skill and knowledge, is to make some functional pieces from native soil. This is something I've wanted to do since I was a kid playing in the fields where I grew up. I collected about 40 lbs of soil from an excavation site, slaked it into a slurry, and sieved it to ~40 mesh. I dried it out on a hardibacker board, wedged it up and let it sit for a week. I netted about 20 lbs of a VERY sandy and short clay body. I decided not to use or test it because of the sandy consistency. I slaked it again and sieved it through 80 mesh which removed about 5 more lbs of fine sand. Dried/wedged/waited a week as before. This resulted in 15 lbs of a still short, but significantly more plastic, smelly clay body of a very dark, grey/green/brown color. It dries to a light grey/green. I'm guesstimating a 35% - 40% clay content??? Given the geology of the area I expected a very iron rich content. There are a lot of gold speckles when viewed in the sunlight that leads me to think Pyrite is plentiful. Maybe mica? The soil is from an alluvial plain about a mile from sandstone formations that was used for agriculture before heavy development in the middle of the last century. I wedged up a couple of chunks to see how it would perform on the wheel. It gave little resistance and was remarkably soft and easy to throw. Like really thick peanut butter with sand in it. I decided I wasn't going to try and make anything too fine or thin because I was afraid of overworking it too quickly. It produced little slip and soaked up a lot of water. I kept what slip I had and let it dry completely. It is very hard to break and snaps apart without crumbling, if that means anything. The 2 items I made had excellent green strength. attaching a handle was an exercise in patience because of how short the clay turned out. I fully expected the handle to pop off in the bisque firing. I also made a 10cm test tile to check shrinkage. Dry shrink is ~6% or 7%. Next, I decided that I couldn't leave well enough alone. I combined equal parts ^10 B-Mix with the native clay, wedged it to homogeneity, and threw a small mug. This improved plasticity, was easier to throw, and demanded less water. It behaved like a sandy B-mix and was a lot easier to put a handle on. I then did a ^06 bisque load in my electric kiln. I was expecting havoc and woe when I opened the kiln, but was pleased with the results so far. The native clay body fired to a deep terra cotta color Pictures do not do it justice. The blended clay body is a light salmon-y color. The native has a bright ring when thumped; the blend a little less bright, even though it has thinner walls (prob. b/c of B-mix?) I have attached before and after photos for consideration. Next I need to determine a suitable final firing temp to glaze and mature my experiments. I also want to improve the workability and plasticity of the native clay body, but I'm not sure where to start. I've read various methods for doing this, but it's like brewing: ask 10 brewers a question and you get 12 different answers. I'm sure that combining with the B-Mix was a quick and dirty impulse fraught with peril, but I can't help thinking it is a viable way to go. What does this combination do in terms of glaze matching and maturation temp? I think the native clay is a bit more straight forward in that it is terra cotta, so there are probably easier options to choose and test. I'm thinking Spanish style of a white or red glaze (clear?). I also want to use some of the processed native soil to glaze with. I've seen it work on ^10 clay bodies, but not at ^6. Thanks in advance for the wisdom. Dave
  10. Don't believe everything you think.

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