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Kevin B.

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About Kevin B.

  • Rank
    Newbie
  • Birthday 11/18/1983

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  • Gender
    Male
  • Location
    NW CT
  • Interests
    Bonsai, Beer & Mead Brewing, Beekeeping, Pottery, and whatever else tickles my fancy...
  1. Claybody Blues...

    Don't know why I didn't think of this first... duh... So I went and tested all my added materials separately with a vinegar soak to see if I could find out where the carbonates were coming from, and I found the culprit... turns out the river sand I use as temper must have some limestone in the parent rock upstream. Hard to take a clear pic since the silt/clay in the sand left the vinegar a little cloudy, but if you take a look below, all the little dark grey spots in the liquid above the sand on the bottom are bubbles. I'd say this shows that I will be able to dissolve out the offending calcium carbonate so pops in the claybody from large granules can be avoided. Also shows I had quite a bit more carbonate than I suspected, amazed I didn't get more pops on my pots. Only thing left to do is mix some treated sand into my next batch of clay and see if the pops are eliminated.
  2. Claybody Blues...

    It's funny you should mention that clay, I almost bought some last time I was up there to play around with. Maybe when I get my wheel finished that could become my standard claybody for throwing.
  3. Claybody Blues...

    Thanks for the input, here's the specs. for the base clay before I add my grit/sand and other native clays/soils to it - I haven't tested absorption on the final recipes yet. I gloss fire it around cone 1 in a neutral to reducing atmosphere (depends on amount of NaHCO3 in the particular "glaze" recipe). When I bisque fire in oxidation it turns both claybody recipes various shades of buff to light salmon pinks. With the additions I use in the claybodies, I know I'm opening up the body and making it more porous, but even with the chawan I've made, they stop weeping after only 10-12 uses, so there's actually not a lot of space in the earthenware even after I open it up. And that's on pieces that aren't completely glazed either as a result of brushing on the bicarb. Once I figure out a the correct consistency and concentration for dipping my bicarbonate solution so I get an even coat, I'm guessing the porosity of the inside surfaces will decrease even more I'm planning on posting all the results of my experiments once I have them - I'm realistically only in stage 2/5 for what I need to figure this process out. I'm basically going off of an old snippet of an article I found from a NCECA conference summary from back in the 70's. And I can tell you that the little glazing "accident" from my second pic above is already sending me in a different direction than what they were trying to attempt in the article. Trust me though, the process I'm developing is a little unorthodox for the potters who like nicely formulated clays with predictable glaze results in a completely controlled kiln, but very cool at the same time. I'm a primitive technologist being a little creative, not a potter. With the exception of the clay, the rest of my materials come from a grocery store, hardware store, or the woods behind my house - no fancy heavy duty fire brick or potentially dangerous glaze chemicals in sight. Just good ol' down to earth simple materials. My goal is to ultimately come up with a process any hobby potter could do on a budget for attractive and functional low fired & glazed earthenware - especially if they're into tea ceremony and want to make their own bowls, like I do. Necessity is the mother of invention especially with these experiments, because as much as I love wood fired ^10 stoneware with natural ash glazes from protracted firings, I currently don't have the budget or the space or time to put an Anagama in the back yard. (maybe one day, but not now) However, if I can completely justify a small wood fired muffle kiln that takes only a couple armfulls of kindling or a few bags of charcoal to fire, then I'm going to try and take full advantage of what is possible with it.
  4. Claybody Blues...

    I had a hunch the white spots were either soapstone or microline, not limestone. Calcium in concentrated amounts will bloat the glaze, but not rupture. Mica typically runs 13% potassium (weight): so I will go with microline for the moment. In a cone 6 firing, that large of mesh size will be very problematic because it would require an extended hold to off gas. So the green would be from potassium, but more so by sodium: most likely both. Potassium is an off gassing hound in a cone 6 firing; the reason it tops my list. Easy enough to confirm: make a simple form and glaze it with a simple (regular) cone 6 glaze. Fire it either to 2190F with a 20 minute hold, or to 2230F with a five minute hold. If this is some kind of microline (which is my hunch), then you should end up with blisters and pinholes. Might seem like a waste, but it will confirm what you are dealing with. if it is in fact some tectosilicate, dealing with it will get easier. Just run the test with a regular load of cone 6 in the future. Nerd I use bottled water to rinse and calibrate my PH meter. I keep it simple. So microline expands from atmo. moisture weeks after firing like limestone, interesting, I didn't know... Interesting though, the rocks my materials are coming from are in the middle of a territory bordered by soapstone deposits to the north and limestone beds to the south, so there is some possible geological overlap. The reason I went to limestone as a first thought was because I literally read about this similar phenomena two days ago in Leach's book and he talked about limestone grains the size of small birdseed being big enough to pop pots and glaze weeks after firing. Hmmm, this might be tricky to test since my kiln is a small wood/charcoal fired raku-type muffle which only really gets to cone 1 or 2 max. And it means I'd also have to learn some "real" glaze chemistry - was trying to do the vapor firing to negate that - oh well... lot to think about. Would all your tests still work at my low fire temps, or do they need to be up near ^6 for the chemistry to work correctly?
  5. Claybody Blues...

    The iron comes directly from the decomposed granite subsoil I added into the clay body - so you're right on the mark with that guess. From what I know about our local granites, they're predominantly very iron rich K-feldspars locked up in a matrix with lots of mica, quartz, and varying amounts of other trace minerals - you'll also find occasional pockets of pyrite and garnet crystals in them. Actually the subsoil itself looks exactly like the body in pic 1, which is great because I wanted a warmer, redder body to put iron dependent glazes on. Otherwise, the base clay just turns out light grey to yellowish/pinkish buff under various levels of oxidation - really unattractive in my opinion which is why I wanted to alter the claybody in the first place. Are we talking bloating during firing or post firing moisture absorption? I know the larger of the particles have swollen enough a couple weeks after to the point where they've popped off small pieces of body/glaze sitting on the counter (pics 2+3). I should have specified before that the limestone in question is at the very center of each pic, the majority of the remaining white specs are actually silica in the form of decomposed quartzite granules. If you meant during firing, the reason why you're not seeing a reaction to the glaze is because there is no glaze in the traditional sense. I was experimenting with sodium bicarbonate vapor firing in a saggar, and that thick green in pic 2 is where some of the molten sodium splashed out of the crucible I overfilled and onto the bottom of the piece - was a fortuitous accident, which I am now replicating and trying to perfect into a process. So it's not glaze like one would normally think, but rather the reaction of molten flux acting on the clay components and melting a sort of glaze right into the pot face. I can tell you that there's no lignite in my soils, so I'm going with naturally occurring manganese from the parent rock - it would explain why a "glaze" on an iron rich clay would go yellowish-green and not orange or red at 1000-1100C (manganese naturally forms green crystals by itself, right?) I'll have to try the pH tests for the clay, like I said all this chem is new to me - I know I cant use my own tap water though, our water softening system uses a potassium based salt. Could trace amounts of potassium also cause the glass to go green? I just realized I've been using tap water to mix up my slip dish and to process all my additives. Man, now I've got a looong list of variables to backtrack
  6. Claybody Blues...

    So I've been experimenting for the past couple months with blending various local materials into a C6 stoneware clay that I've used successfully for many years in pit and bonfire firings to give it a bit more character for raku firings. I've settled on two blends for the time being, one lighter and smoother in texture, and the other darker and more gritty. They both take the thermal shock of firing well and give me the color and character (or taste) that I'm looking for, but they both share one small problem. I think I've figured out a work-around to fix it but I thought I'd run it by the more knowledgeable folks here to see if there's any variables I'm not taking into consideration, since I am a relative newbie to this clay chemistry stuff. The problem I'm having is small particles (1-2mm) of limestone from the local silts and grits that I use popping out of the clay/glaze surface after firing. Shouldn't be a huge problem right? Just use a finer mesh sieve to remove larger limestone particles, right? Well, unfortunately I can't do that because I've (stubbornly) decided the texture of the clay is perfect with the larger particles of grit I use for temper and I don't want to run it through anything finer than a 1/16" screen. (photos below) I have to mention as an aside finding limestone grit in my native iron bearing soils was not a surprise - heck, everyone around here who uses well water knows how hard with iron and carbonates it is. I just didn't know to what extent it would show up in the clay until I fired it. So, since I decided I can't sieve it through a smaller mesh, I've thought about dissolving the particles with vinegar. We've always used vinegar to get rid of calcium carbonate build up on our glasses and our house humidifier, so I thought using some apple cider vinegar in lieu of water when I'm sieving the limestone bearing soils before I mix them into the base clay could alleviate the problem. Plus, if I remember right, I read somewhere that some old time potters mixed in vinegar to help with plasticity. Unless there's something I'm completely missing this sounds like a win/win right? Please forgive the photo quality (glaring highlights), don't have a lightbox setup yet to photograph my stuff.
  7. Native Clay, Odd Smell...

    Wow! Haven't been able to jump on here in a few days and I am just floored at the response and the information you guys/gals shared. Thank you! First off, I should probably clarify/answer a few things... Seems to be the case - after a few days of oxidation in the bucket the smell has almost dissipated, it now just smells like organic heavy mud. Correction, I thought I was using 1/8", I was actually using 1/16". Leaving the silt and small grit in is not an oversight in my case, it is deliberate. Remember you're talking to someone who started out in experimental archaeology. I'm aware of mesh sizes, but in doing primitive and native style pottery "mesh" is a bunch of modern western mumbo-jumbo. But seriously, thanks for your post, if I ever decide to really process the clay I'm going to follow your advice to the letter. Where I live it's all dry forested rocky hill tops and soggy wetland/river valleys - I'd be amazed if I found clay where it's dry. The most local clay producer near me (Sheffield Clay, in Sheffield MA) takes their stuff from what was an ancient riverbed. Finding clay near water or where there was water seems to be the norm in my area. If you have a deflocculant about, this sounds like a good thing to try, at least as far as seeing if a significant "colloidal" layer forms. Obviously if the sample is acidic you may need more deflocculant than normal. - If this doesn't work, can your sample really be similar to that used for native pots? - If it does work, maybe your current sample gives an over-flocculated suspension? How native clays were processed in my neck of the woods was - clay deposits would be dug and dried, smashed/ground and then sifted through a woven basket to get out the larger stuff before re-wetting and shaping - this left a lot of silt and grit in the clay which acted as temper to help the pots withstand the temperature fluctuations in firing. It's very rough stuff, but it did its job. I've seen examples of early to middle woodland (approx 3000 yrs old) native pottery taken from the ground close to where I found this clay, and all I can say is the composition looks almost exactly the same for the two. Whether it's the same clay or not - well, that requires some chemical testing for which I currently do not have the funds. (Nor do I think the museum who has the sherds in their collection would want to give one up to a hobbyist who is just curious about their composition.) Will do! Lots! And there were even more before that time frame. Although here in the northwest corner where I live it probably would have been Schaghticoke, Potatuck, or one of the smaller local tribes. In fact, the lake that's a 1/4 mile from where I dug the clay is named after Chief Waramaug who was the sachem of the Potatuck from 1725-1735. The later woodland period pottery of this area has quite a bit of "Iroquois" influence because they traded with the Mohawk to the North West in NY. Before that is a much simpler style of chord marked and incised earthenware. Whew! Now that that's done here's what's been happening over the past couple days... After letting it settle for a few days I carefully poured the water off the top of the clay, and was able to get all but an inch. This I mixed back in to make a thick slip, which I then poured in to a dryer setup I've used before for clay - basically a 2'x2' frame made of 1x4 resting on top of plywood into which I put 2 layers of heavy cotton duck to wick away moisture. Interesting to note - when I went to mix it back into suspension to pour out, what I thought was a solid settled layer was not a solid compact layer at all, it was still in suspension somewhat. Felt like I was putting my hands through syrup, not soil. Now all I have to do is wait for it to dry to the point I can use it - should be a few days. I'll keep you guys updated on its progress. Pics to come soon - having trouble uploading. Off to the FAQ section I go!
  8. Native Clay, Odd Smell...

    Thanks for the response, it did have a pond scum/fishy/algae smell before I washed/diluted it but it dissipated soon afterwards (made sure to not get a whole lot of scum when I dug it). Burnt wood might be the answer, but how long does that smell stick around in the soil? Family hasn't had a bonfire on that property in 20+ years, and before that it's been probably close to 200 years since the farmers in the area originally cleared the land for grazing.
  9. Hi All, long time infrequent visitor to CAD, first post - sorry it's a bit of a long one. So, through a long series of events, I'm coming back to ceramics after several years of not touching any clay. As an Anthropology and Archaeology student in college (with an art history minor) I learned to make pottery with experimental archaeology - basically recreating local examples of native pottery using the methods and materials that were used centuries ago to make earthenware. However, what we learned on was a somewhat locally produced modern processed clay body with lots of sand mixed in to withstand bonfire and pit firings. Don't get me wrong, I still use that clay body and experiment with it still since it is totally reliable in a pit firing, and even with all the grit added it's a pleasure to work with, but I've always thought of using clay harvested with my own two hands. As chance would have it, I have a relative who lives in town and has local clay deposits popping up all around the spring fed pond on her property, and she recently gave me the OK to collect clay. What's more, her house is literally less than a mile from an area with a known archaeological ceramic history. (I've actually worked with the head archaeologist overseeing the current dig in the area, lovely woman with a wealth of information on our local native peoples and their material culture. - small world, right?) So this past week I collected some rough clay from the pond, made a thin slip and ran it through a 1/8" screen to remove the small rocks, gravel and sand. What I was left with was a clay that dang near matches what has been found archaeologically - gritty, silty, and predominantly large clay particles resulting in a mildly plastic, sticky, grey clay body that almost entirely settled out of suspension and left a layer of clear water in under 24 hours. In other words, good thing I wasn't planning on making terra sig from it, I'd have to dig a ton just to get a couple pounds... However, it suits my purposes perfectly since I'm going to me using it for hand-built recreation native pots and possibly some traditional raku-style chawan if it proves plastic enough. Here's where it gets interesting... Remember I mentioned an odor in the title, right? While I was processing the clay I noticed a mild aroma. At first I couldn't put my finger on it, but then I realized the closest thing I could describe it as was the same leathery, smokey smell you get from a German rauchbier that's been made with beechwood smoked malt. Now, I was going to have the clay tested anyway to see if it's foodsafe, but this odor has me wondering if there's any point to going ahead if there's already some known chemical or toxin in the clay resulting in this aroma. Or maybe it's because the clay is fresh and has a lot of organic material to rot out, I honestly don't know. Thing is, I've poured through all my ceramic books and searched the net to see if this smokey smell has ever been documented, but I haven't found anything where anyone describes this phenomena. So I guess that's my story and question all rolled into one - anyone know what would cause clay to have a leathery/beechwood smoke odor?
  10. The Dreamer And The Cynic

    Being an artist/craftsman who has been working a 9-5 job to just pay off bills, and recently figured out what his life is lacking and is coming back to the arts, this rings soooo true. Thank you, this is now my daily inspiration.
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