Kelly in AK

With the gas kilns it’s all me, and that’s been a long slow learning curve. It started with “don’t blow yourself up.” My experience with electric kilns is a different. I count on electricians. However…I learned, as many do, electricians in general are unfamiliar with kilns. If you find one who is into kilns, they’re a gem! I’ve learned enough to do a lot work myself, but I’m not yet confident to flip any switches till a pro checks it over. Except the thermocouple. I don’t need a pro for that.

I’ll throw this out. The worst/best/most dramatic fuming effects I’ve seen were chrome and tin. The tin glazed white pot is now pink on one side because the one next to it had a chrome wash. Next is copper, in reduction at least, pots near the pot with high percentages of copper in the glaze, um, may be affected. Sometimes a red splash is provident, others it’s the ruin of a pot. Cobalt is insidious. Practically invisible until fired good and hot. Then it’s the blue that just doesn’t quit. I haven’t had so much a “fuming” problem as a “How did that get there?” problem with cobalt. Soluble metallic salts? No thank you. I prefer most metals in a non soluble form. Except sodium.

20” x 20!” Large tiles indeed. No mean feat in my book, 12 or 18 hundred degrees, you’ve passed some hurdles. If I had two sets of tile from one body, one set being fired to 1200°F and the other fired to 1800°F I believe I could tell pretty easily which was which. So, yes, imagine you could too. As mentioned above, get it wet. Try to dig in or scratch it. Properly fired bisque ought not yield to that with a fingernail or wooden tool. A metal tool (steel) can scratch soft bisque with effort, but I’m getting more specific than I intended. You might ask me about what’s proper, then I’d be in trouble. If handed a piece of bisque ware and asked what temperature it was fired at, I’d have to ask a lot more questions before I ventured a guess. Be careful with those tiles, glad you fixed your settings. It’s a blip. Oh yeah, cones! Use those until you have no reason to wonder what your kiln is doing. And again when you do have reason.

I rely on sanding the foot (after glaze firing) to take care of this. I do polish with the wooden part of my tool when trimming, but that alone doesn’t do it. And if a pot warps in drying I’ll slide it around on a wet ware board to flatten the foot, which pretty much ruins that burnished surface. 220 grit to knock the sharp edges off followed by a quick 600 or 800 wet sanding to polish it a bit. It’s not too involved, a brief operation on a pot by pot basis. My feeling is if I can slide the pot on a tablecloth without any snagging it’s done.

Words from mages: Fewer pulls, Tend your pulls towards the the final shape. Be aware of the architecture of an arch, how it supports what’s beneath. As little fussing as possible. Work dry as you can. Good luck.. Heat guns are aggressive. Takes some finesse to not crack things. Embrace trimming.

I appreciate the updates on this @Hulk, I made a few bats of Hardibacker for my partner about a year ago but she hasn’t used them yet! My wheel doesn’t have holes for bat pins so I haven’t bothered to try them either (I’m accustomed to using roofing felt bats). We both regularly use it for ware boards though. The belt sander is a worthwhile step.

Nice!!!

One thing that’s useful to know is how your clay develops over a temperature range. It could be that simply firing to a different temperature gives you the color you’re after. See these links from Tony Hansen’s Digitalfire website: https://digitalfire.com/picture/baftunycyg https://digitalfire.com/picture/5m5aJocQuR

I’ll confess, I’ve done this a couple times. In my defense, once was the wrong push of a button, the other was learning to bisque in my gas kiln (I even had some pots that were only vitreous on one side!). Glazing those pots was such a chore. I heated them, had to use tongs or a glove to dip, and wound up holding each one upside down for minutes to keep the glaze from flowing down to the foot. I’ll testify glazing took way too much time, and I don’t do anything complex. I’m a dip it and done kinda guy. I’d have to be very desperate before I repeated that experience.

Hey there, Welcome. I appreciate your sharing what you’ve been doing and results. I can’t say I have an answer to the problem, but I’ve certainly experienced it. Inconsistent behavior from a single recipe. When this comes up in discussion concerning recycled scrap people will often say it’s about losing a percentage of the fines and suggest being careful not to discard any slip. I’m not convinced that’s the main problem. I believe it’s more due to particle wetting and ph. The conclusion about ph comes from the experience(s) of recycling a few hundred pounds of scrap that’s been sitting in a bin for months under a layer of water. Total slop, fully wetted. What went in was nicely plastic. What came out after dewatering and pugging was horribly short. So the thought is, after sitting so long, solubles in the clay leach out and change the chemistry. I’ve heard vinegar as a remedy for ph problems, but can’t speak to that with experience. Perhaps someone else can. As to particle wetting, I think it’s a more complex process than it appears. Your description validates this. I’ll point to Veegum, a plasticizer I regularly use. The manufacturer states it will not achieve its true plasticity unless fully hydrated, and that is no mean feat. Hot water and a LOT of mixing. One pound will completely gel a five gallon bucket of water. If you just dump it dry into your clay mix it will never hydrate properly, even if well dispersed, and you’re just wasting it. Those are my thoughts. Maybe mixing your clay on the more wet side, or perhaps slaking the more plastic ingredients (ball clay) overnight before any mixing occurs could make a difference. Good luck!

If you can tell people what kind of kiln you have along with what kind of glazes you plan to use, that will make it easier to help you. Earthenware tells us you're working in a range around 1800-1900° F If you're using glazes, those should have instructions on the container listing a "cone" to fire at. That cone number is related to temperature as well as time, Ultimately, if your kiln doesn't reach temperature, you could sit there three days and the glaze will never melt.

Another approach to consider is incising the lines, filling them with underglaze, then wiping away the excess. The drawing is different because you’re drawing into the clay instead of on it, but this technique can produce very fine, crisp lines. Lorna Meaden’s work comes to mind. The technique has its own learning curve, you’ll find yourself now looking for the perfect incising tool, haha! Underglaze applied using fine tipped applicators, like @Roberta12 mentions, are the best thing I’ve seen for no frills unencumbered drawing of fine lines. Underglazes are generally predictable and won’t run or bleed. The tools clog easily, so you need a straight pin or fine wire for a stopper when not in use.

You should not be paranoid. You’re likely to have more exposure to free silica taking a walk on a dry breezy day than sanding greenware for five minutes over the sink. No harm in being cautious, but you have nothing to worry about. A thought for future reference, I like to dampen things with a sponge then scrape using a steel rib if I need to remove material

While it’s not quite the same as what you have to deal with, it is fun to watch these old potters glaze big pots. And they glazed them green, which is wild to think about too. Isaac Button glazing some big crocks (around 4:30): Burlon Craig glazing a crock and a bottle (around 2:00):

Sounds like a good plan. It’s a big beautiful piece! Worthy of a little more caution than normal. I’m hesitant to offer straight up advice, not knowing all the particulars, but I will suggest applying your flashing slip thin. Mostly because the piece will be dry and you want to avoid issues of fit/shrinkage, but also because a thin layer is sufficient and won’t hide the texture.

It’s possible for glaze tension to crack a piece in half, but it’s unusual. For example a very thin piece, made of clay that’s over fired, glazed too thickly, glazed only on one side, and with a glaze that has very compressive fit is a good candidate. That said, I do soda fire at cone 6, have done dozens of firings. My own work, my own kiln. Ninety percent of the work is glazed only on the inside and about 1” down the rim. A flashing slip is applied to wet and leather hard work (50/50 Helmer and neph sy). I’ve never had this problem in my soda firings. Michael Cardew discusses it in Pioneer Pottery, he treats it under the section on clay body defects and refers to it as “shattering.” It is a real thing, but generally happens under a particular combination of circumstances. I share his opinion that it’s best understood as a clay body defect.

Reaching cone 6 with wood is no problem, but as @neilestrick said, you’ll not get that juicy wood fired look at cone six…without some help (flux). Ash begins sticking to pots and building up pretty early on, at bisque temperatures. It stays dry and crusty until cone 9 or 10. Spraying soda ash in will flux it at cone 6 though. Some kiln designs aren’t made to emphasize ash buildup though, Olsen’s fast-fire comes to mind.

I throw sit-standing. The wheel is belly button height when I’m standing, slightly higher when I’m sitting. The stool is an ordinary stool with adjustable legs set high so I’m upright with legs extended, but weight rests on the seat. There’s a wedge shaped cushion, thick and comfy, tilting me toward the wheel (carved out of an old memory foam mattress). The thing I like about this posture is the ease going from sitting to standing. It’s a seamless enough transition I couldn’t say how much time is on my butt vs. me feet. I tried angling the stool by adjusting the legs and it didn’t feel good. The angled padding with a flat seat was better. Everything else, so far, is done on my feet. Lately I’ve been doing a lot of hand building, if this continues I may explore some more seating options. I have two table heights, one for wedging and rolling slabs that’s around crotch height and another six or eight inches higher the banding wheels sit on. Once a piece is assembled I raise it closer to my face to do more finicky operations. I was impressed long ago by John Glick’s article, https://studiopotter.org/sciatica-and-back-potters-journey, to consider throwing standing up. About the same time I read that I was researching North Carolina potters from the 19th century and noticed they threw standing. There were itinerant throwers who would go from place to place, throw the ware, then move on. Throwing was all they did. I figured if these guys wanted to stand while throwing five gallon crocks there may be something to it. Revisiting Glick’s article makes me think more about that back support. My back is telling me it really looks helpful.

Anything organic in the clay is going to rot sooner or later. Balancing the strength of antibacterial agents against their negative consequences is one way, but drying the clay in thin sheets to use as needed seems like a good solution to avoid that issue altogether. Paper clay has unique and very useful properties, to be sure. The amount of fiber in the clay is an important variable as to how it behaves. If you come at it from the direction of how much clay you have to add to make paper pulp sculpt-able and fire-able you’ll get one material, or, from the direction of “how little pulp can I add to make this clay more plastic and forgiving,” you’ll get another. The term paper clay can mean different things to different people. For fun I once made a clay that was more paper than clay, with a liberal amount of Veegum to plasticize it. Made a couple pinch pots and tiles, then fired them. Very lightweight stuff, a fascinating ceramic detour. The most common useful formulas for handmade ceramics suggest <20% by volume paper, mixed in slurry form, as @Callie Beller Diesel mentioned. I usually have some on hand for students attempting “emergency repairs.” Because it’s mostly used for repairs, I also add a little soda ash (around 1-2%). Of course students always get a lecture first about why the crack happened in the first place.

Concrete floor with a drain. Very satisfied with ease of cleanup. Vacuum (HEPA filter), flood with water, squeegee it all down the drain, then flood the drain for good measure. I have a couple of puzzle mat squares in places I stand a lot, but not at my wheel. I throw semi-standing: elevated wheel and a tall stool with an angled foam cushion (Big cushion!). It makes the transition from sitting to standing much easier and I’m mostly off my feet in that spot. While I’m at it…L4&5 on some days (lifting), C5,6,&7 others (decorating and trimming), and shoulders whenever they decide to hurt (usually wedging). It hits the day after. Occasionally they’ll all go at once. Tylenol days.

I agree with @Bill Kielb, glaze fit is notoriously hard at low fire temps. It’s easy to imagine quick cooling is the culprit, but it’s unlikely that’s the cause. Industrial producers have astonishingly fast firing cycles, literally three or four hours from green to glaze fired, no crazing. It’s not deep magic, it’s because the glaze fits (they do have some tricks, but they’re mostly centered around avoiding other defects). I’m happy to confirm that most of the things you’ve tried will have no bearing on your problem, none. The one thing you mentioned that might is trying a variety of clays. The glaze is shrinking a lot more than the clay. The other avenue to explore is temperature. In the range you’re firing at glaze fit can change radically within a cone, even half a cone. I say that from experience because I fire my work to cone 03, low fire. The clay is unique, and the glaze is formulated to fit, but a cone lower and it’s going to craze, a cone too high and the pots will dunt. This narrow range is true for many red earthenwares and clays designed to vitrify at low fire temperatures. Also, I should note that one of my kilns is fiber board and cools very quickly. It’s recently retired, but I fired dozens of glaze loads in it. Shut off at 10:00 pm and cool by morning. No crazing. That’s another reason I’m confident quick cooling is not the root of your problem. I suggest you approach the two variables of clay body and glaze firing temperature (Some people fire their bisque quite high and do a lower glaze firing, I can’t speak to that with experience so won’t suggest it. It may well work.). Your cone 06 glaze might do fine at cone 04 and actually fit. I regularly fire commercial cone 06 glazes to 04 and 03 without problems. There is the avenue of glaze formulation, but that’s an entirely different can of worms.

Not long after I got really into clay I realized I needed my own kiln. It’s the one thing that you can’t just whip up on the fly. If I have fingers and clay I can make pots, all the other tools and gadgets come along easy enough. No kiln, no pottery, though. A big hot fire works, but it’s not long before you see that putting a ring of bricks around the fire works better. Then making inlets for air, then a top, then a chimney… Next thing you know (many years later and many kilns later) the fire pit is a 15 cu. foot downdraft and instead of burnished terra cotta I’m doing cone 6 soda. Yes, I have my own kiln. I’ve made several from fiber and a couple from fiber board. I’ve gotten away from that miracle material though, I have enough risks in my life without worrying about respirable silica. My kiln is fairly low tech and firing requires that I babysit most of the time. Along this evolution was a cone 6 wood/soda kiln, which was a blast. The occasional columns of thick black smoke and endless need to replenish the woodpile nudged me to gas though. Every firing produced anxiety the fire department was going to show up. An electric kiln is on my wishlist, I have access to a few and that’s how my bisque is usually done. I can bisque fire in the gas kilns, it’s not so bad, just adds a lot of time to an already long process. Pushing a few buttons and going to bed is hard to beat.

My main concerns are about the foot bearing some relation to the form. It’s the conclusion of a line that starts at the rim and ends at the point it touches the table. The feet on my pots vary. Some don’t have “feet,” proper. Others are distinctly footed. I just want them to look right, it’s not always successful. I usually have an unglazed exterior, soda firing takes care of the outside, or terra sigillata on the local clay, so I’m seldom fighting glaze drips. Nirvana is when the foot is shaped right, I’ve preserved the wire marks from cutting the pot off the wheel, and I’ve managed to carve a lovely deep logarithmic spiral from the center to the inside of the foot. All while removing the right amount of excess clay to make the pot balanced. I aim for it every time, happens about once every never. Two things I directly avoid are the suction cup effect @Callie Beller Diesel refers to and sharp/crisp angles (“That’ll chip in the sink.”).

Very cool! I find using locally available clay both deeply rewarding and challenging. Since I don’t have issues with lime or calcium (That I’m aware of, haha!) I can’t speak to that. My clay is probably very different from yours. I have some thoughts that may be relevant though. The first is, I wonder what you’re expecting of the clay in terms of “settling out properly.” I too use a wet or slip process to make what I collect useable. When I get the water/clay ratio how I want, it mixes in the bucket as a whole circulating vortex. It’s fluid. Not necessarily watery, but it flows enough that I’m not working any harder than I have to with the mixer. I may have understood this bit wrong, but there’s no way I could fit 60 pounds of clay and all the water in a five gallon bucket. After I get it mixed it has to go through a sieve, it’s got to be fluid. I think 20 pounds of clay is about all I could fit in a five gallon bucket full of water. Maybe. Long way to say, perhaps you’re not using enough water for it to settle out, no matter how long you wait. The next thought goes back to flocculation. For a while I flocculated my clay with epsom salts to improve plasticity. It went from pourable to pudding state instantly. So I can’t say about vinegar specifically, but about flocculation generally, I wouldn’t expect flocculated clay to settle. It’s the very reason I flocculate my glazes, to keep them from settling. If I wanted clay to settle out that would be the last thing I did. (It was, literally, the last thing I did before clay went into drying trays, after letting it settle a couple weeks then siphoning off the water). I could ramble on… I’ll just finish by saying don’t underestimate the potential information you can find through observation, record keeping, and testing. You will discover new things as you run the clay through the kiln, there’s a trove of data there. Many sound conclusions about the chemical composition of your clay can be made through testing you can do personally. Good luck, and hoping to hear more about how things unfold.

I have a small gas kiln (8 cu. ft) made from fiber board. Two layers of 1” board. Has no problem getting to cone 6. It was cheap and easy to build but I won’t build another. I agree with the points @neilestrick made and have a couple more. Fiber board has its strengths, being rigid and super insulating, but it has some drawbacks. One is that it will shrink. Once you fire your kiln (unless you pre-fire the boards) you’ll have to re-fit it because big gaps will form. The other is that it’s really friable. As bad as fiber blanket, in my opinion. Even though it’s rigid it’s not strong. Every time you lift the lid or open the door, you’ll be abrading it. The wear and tear is one thing, all the respirable silica it releases is another.