Kelly in AK

In Hamer and Hamer’s “Potters Dictionary of Materials and Techniques” there is a diagram of a crack, labeled “crack f” that looks very similar to your picture. The causes the list for this crack in glazed ware mostly have to do with a mismatched COE. One particular note mentions glaze that is thick in relation to the bottom of a piece, the action of the glaze fluxes the clay of the bottom more than elsewhere. I read that as having to do with the thinness of the bottom as much as thickness of the glaze.

Thanks for reporting back! I’ve used that same primer and it’s tough stuff.

Mosquito larvae enhanced the plasticity. (Just kidding. Don’t try it.)

At school I occasionally end up with a few different clay bodies for the students. Sometimes other schools will give away clay that’s too stiff to use, since I have a pug mill I always get as much as I can. After fifteen years doing it, the biggest problem remains the “other stuff” that sneaks into the reclaim bucket. The pugger mixes everything into a homogeneous body and it all starts as cone 5/6 clay. There was a year I got some porcelain and that required a few trips through the machine to get it mixed in well (didn’t have a pugger-mixer at the time, just a simple pugmill).

Since you caught me right after I mixed up a bunch of glazes and tests, my shopping list starts with a digital scale! The leftover money goes to Veegum.

As Neil said, get a big enough tank to start with. “Almost big enough” will freeze at the worst possible time. http://wardburner.com/tanksize.html

So, for science, art, and the good of the order I gave buffing it a shot. A couple different ways. No appreciable change. Shot it with some spray varnish and that glossed it up. Definitely shinier.

I had some gold paint lying around and thought, “Why not? I’m sure I’ve got a pot somewhere I wouldn’t mind defacing.” You can faintly see the brush strokes, which wouldn’t happen with spray paint. Pretty golden though.

I can’t add much, as people’s suggestions have covered most of my thoughts. Keeping the pots in one flowing line from wet clay to glaze fired ware is the biggie, no backtracking around the studio. The closer wet clay is to the delivery door the better. I also have to wholeheartedly agree with LED lights. I wasn’t sure because I’m not fond of the color, but my partner likes it bright so I put a couple in our studio on “her side.” They were so great I quickly put two more on “my side.” They’re like shop lights, you can get them with a plug or to hard wire in. One mistake I made was buying “high bay” style lights, which are meant for a really high ceiling, unless it’s 20 or 30 feet high it’s like a spotlight. I traded it in for ones the same brightness but made for regular height ceiling. Beautiful looking space!

Holy wow! On your way, looks like. I found out about anhydrous borax by accident. I had a bag labeled “borax” among a bunch of stuff I bought from a retired potter. I went to put some in solution and the dang stuff didn’t dissolve!

Woohoo! Refreshing update. Thank you! You know you’re lucky to live so close to the clay mine, right? Wish I could pay someone to to dig my clay up for me. Something about borax, in addition to challenges it makes with glaze formulation and application, consider that it will flux your clay body (it soaks in). It can change the fit of glazes, perhaps in an inconsistent, unpredictable way. I’m talking about having half a kiln load shatter on cooling, or having a mug crack clean in half when filled with hot water. Not conjecture, I know someone personally who did work with borax washes and these things happen. There is something known as calcined borax available that’s less soluble (apologies if it’s been addressed earlier in the thread), relatively less expensive than frits, and still has a sort of “purity of material” I sense you value, which could be worth exploring. Just saying stay loose and be ready. You’re doing great work, I love it!

What @Callie Beller Diesel said! Copper carbonate would be my go to oxide/carbonate for greens, but chrome is green too. I don’t like it, but it’s definitely green. Teenage Mutant Ninja Turtle green is what comes to mind. Chrome is very refractory, plays differently than others. Ok, that’s out of my system. I haven’t real world tested these things enough to dispense much advice. As mentioned, iron works quite well without extra flux but will make glazes crawl if applied too thick (chrome does the crawling thing even worse). I mix 2% Veegum with iron oxide to keep it in suspension, water “to taste,” so it applies right. A lot gets wiped away with a sponge, to accentuate textures. Then again, I’m soda firing, so that’s like an external flux. Your results may vary. I can say copper goes from pale greens, to deep green, to black, to crusty black, quickly. It’s sensitive to thickness of application and affected strongly by fluxes. I wish I could be more definitive, but Callie nailed it closer than I can.

That rich red! Looks like it’s on fire. Beautiful.

Depending on any Internet restrictions in Malawi this might work, it’s how I read the book: https://archive.org/details/pioneerpottery00card l’m in over my head if I start talking what type of glass, what proportions, and the procedure for such a glaze. Stoneware potters of the southeast USA were well know to use this type of glaze a couple hundred years ago.

Please find a copy of Pioneer Pottery by Michael Cardew if you haven't. His words could be gospel for you. A possible addition to your available materials: glass cullet? Glass, clay, and ash are a historic glaze. Caustic to apply and laborious to make, but essentially free to the potter.

A seemingly simple request suddenly becomes a daunting ponderous problem. “I just want a clear base glaze I can use to start from!” I’ve been there, so first let me say, it gets better (not sure about easier, but definitely better). Mine, 20 years ago, was “How do you make floating blue?” Thus began the Odyssey. Here are my assumptions: You want to make pottery that people can use. You want to mix your own glazes, that you can adjust and color, and experiment with. One reason is so they’re your own, another is it may be less expensive, and finally, it’ll be much more fun than buying a jug of stuff from down the street. To start with, @Min asked what boron frits are available to you. That’s a question you’ll have to work out. Glazes in your firing range need boron and the way we potters get it is from frits. I’m afraid I have no sense of the intricacies of of ordering ceramic supplies in the UK, but you’ll be looking for only a few specific frits. Ferro frits are popular and available in the US, many glaze recipes use them, but there are also tables of equivalent frits from other sources. “Fusion” is another brand name of frit. The term “calcium borate frit” in a recipe is just vague enough to cause trouble. Ferro frits 2134, 3124, and 3110 appear often in cone 6 glaze recipes and are known quantities of each element in them. . In my case, there is no store (in Alaska) I can visit and grab a bag of frit 3124. I have to order it, so I do. There are some recipes to be found onTony Hansen’s Digitalfire website, which can be counted on, but you’ll always learn more than you planned. Stick this in your search engine: “A clear cone 6 glaze base digitalfire” If you had unlimited selection of materials, then people would just flood you with recipes, which be it’s own problem. So, you gotta know just what you can get before people can suggest useful recipes for you.

It’s wonderful! Just start. 60 glazes is an awful lot, maybe pick 20 and make a tile for each, then another 20 tiles for combinations, to get rolling. Honestly, just pick 10. Two glazes together can be very different depending which one is on top. Thick or thin applications will make a difference. 60 glazes, you’ll spend your life making test tiles, haha! Start firing them so you know which ones you love. I should have such problems.

I have to agree with what’s been said . A tile body, stiffer clay to begin with, that’s how tile makers do it . Non plastic clay in a hydraulic press Using plastic clay that shrinks a lot, I’ll share what I do to keep thinks flat. I’m a rolling pin guy, I always flip the slab and roll it in various directions (In fact, I beat the lump flat with a mallet before I start and strongly believe that makes a difference. It’s analogous to compressing with a rib.). With a slab roller it’s even more important, roll it it with a pin in the opposite direction of the slab roller. Compress both sides with the rib. Next is to flip the pieces over after they’ve dried a little, just a few hours. So much shrinkage happens in that first little while, it sets up the warp before you see it and everything you do after that is for naught. A proof is to cut some 3 x 10 mm slabs and measure them after three hours, then again after 10 hours or overnight. The lion’s share of drying shrinkage happens early on, it needs to be even on both faces of your coaster.

It’s a legitimate question. I have programmed every segment of both bisque and glaze firings so I could have a sense I knew what the kiln was doing and evaluate the pots based on that. It didn’t last long. I can see the schedules in the manual, I’ve got no reason to believe I can make the kiln work better than the people who designed it. I did give it a good, honest try. Fewer button presses. Less to keep track of. Cone fire. 04. Speed (depends on how much of a hurry I’m in). Hold, if I’ve got some dodgy, gassy clay. Preheat is the revolutionary setting that took way too long for someone to come up with, no more explosions. Finally. That was the only real reason I used ramp/hold in the first place. That said…it seems like your schedule ought to have gotten you there, so please pardon my smarty pants opinion. You’re using cones, you will definitely know what your kiln is doing. I can be a simpleton. Celsius still eludes my grasp (not so much targets as rates, anymore). Try the cone fire mode though, if you haven’t.

I’m slow on the reply, sorry. Everything @Rae Reich said, just adding another affirmation. A greenware fix is preferable if you can pull it off. In addition to vinegar, people have had success with adding some paper fiber (toilet paper) to the slip for attaching bone dry bits together. Definitely should try the greenware fix first. If it’s not resolved after bisque then glaze will do it in this case, because of the way the piece rests. You’ve got it. Get both parts wet so when you push them together glaze is intimately in between them. Ideally you do this right before YOU load it in the kiln, then it doesn’t get moved about once the fix is made. That’s really the critical bit. It’s not ideal, and assumes you can be the one responsible for putting it in the kiln, but I’ve done it successfully many times with student work and my own. As long as gravity is in your favor, the piece at rest with nothing supporting it will sit like you want it to, glaze will fuse the parts together. I sense you understand glaze has some volume, so just brushing some on each side and sticking them together isn’t the same as fitting the pieces while the glaze is still fluid. I don’t want to make it sound harder than it is, but I don’t want to give the impression there’s nothing to it either. It will work.

I can’t speak to the wire idea, never tried it, haven’t a clue. I do notice that gravity is in your favor here, glazing the bits together will likely work. Since it’s a sculpture and not subjected to repeated loads (like a handle, for instance), I wouldn’t hesitate to rely on glaze to fuse the pieces.

Thanks @Hulk and @Bill Kielb. I get by, but I have a lot to learn.

I’m thinking about adding some safety to my kiln, finally. Too many hours spent fretting I’m going to make a spectacle of myself. So I’ve been wading into the world of baso valves and see it’s a little more complex than I thought. The question I think I need to answer is whether I need high pressure safety valves. The baso valves from big clay retailers are the H15DA, rated to 0.5 psi. Ward Burner sells that one as well as a high pressure one, the H19RA rated to 25 psi. Now, the nitty gritty. My kiln is about 12 cu.ft. powered by two MR100 burners, propane. I have a variable regulator at the tank and that’s what I use to adjust the burners. By the time I reach temperature it’s sitting around 3.5 psi. Seems I need the high pressure baso, but wanted to ask here in case I’m understanding things wrong. I also see a note on Ward Burner site saying the pilot light for high pressure valves needs to be regulated as well, so…another regulator. Two. Any feedback is welcome.

I’ve used PZN clear from Clay Art Center in Tacoma with my students for years, no problems. It’s a cone 4-6 zinc free clear, premixed, dry.

Potters have their own kind of white powder problems.