Kelly in AK

I see rounded edges on the glaze along the crack. It’s not a dunt, it was there before the glaze melted. This is a complex form, if the walls are attached at a different consistency than the slab it’s going to set up big tension. I also notice a lot of sponge marks on the exposed clay surfaces. It suggests some re-wetting/overworking happened, complicated shapes in tension don’t like that. The crack was either already there (happened in the greenware stage but wasn’t evident), or it happened on the way up. At the risk of sounding like a parrot, there are bodies much better suited to this kind of work than B-mix. That said, it’s always good to re-evaluate technique when unexpected things like this happen. This article by Vince Pitelka may also be helpful: https://www.vincepitelka.com/wp-content/uploads/2021/06/Rolling-Slabs-Platelet-Grain-Structure-and-Clay-Memory.pdf

I’m not sure how well Sharpies hold up on a pot, I haven’t played with that. I can verify these (Pebeo Porcelaine markers) make it through the dishwasher when used according to the directions. It’s like a paint pen, let it dry overnight, bake in the oven. There are various colors available, they’re mostly transparent so show up best on light colored clay/glaze. The link is only to show what I’m talking about, not trying to sell anything here. https://www.amazon.com/PEBEO-Porcelaine-Markers-Anthracite-Heat-Resistant-Dishwasher/dp/B005KOH1OY

Keeping moist clay moist sounds like the real problem here. Easy solutions posted above. I dig and mix my own clay. Not counting digging, hauling, crushing, and sieving (if only all that could be done by faeries), it still isn’t economical. If you’re trying to save dollars look somewhere else. Having premixed moist clay delivered to your door is the pinnacle of economy. If, on the other hand, you share my mental disorder, one that is relieved only by making one’s own clay body, knock yourself out. You won’t need a health club membership, so you’ll save a little money there. I wouldn’t discourage it if you have the right equipment, but will reiterate that it’s not economical to mix clay from raw materials until you’re doing at huge scale or have a very peculiar special body. I think everyone should try it once, then you can know.

It may well be the change in clay body if your technique and the stage you’re burnishing at hasn’t changed, but generally if you burnish things when they are leather hard they will dull as they dry. Brush the pot with water (after it’s completely dry) then burnish it again, it’ll stay shiny. The surface has to be damp to burnish but the pot should be dry. If you do more pots get them as smooth as possible in forming and trimming stage (a non groggy body is best), let them dry, and then rewet the surface and burnish. Also you should know that regular bisque temperatures, 06-04, will dull the pot too. I can’t say exactly when that starts to happen, but I think it’s around cone 016. If you use terra sigillata you can go higher before you start to lose the surface. Terra sig from OM4 will stay shiny at a higher temp than that made from Redart.

I know for certain that different clay bodies shed their water at different rates. The most remarkable I’ve experienced was a body made of two parts OM4 and one part pumice (it was pumice I dug up from a deposit in Utah). I regularly fired it from greenware in a raku kiln in less than three hours. It was pretty awful as a clay body, even with all that ball clay it still wasn’t plastic and never got very strong. It melted around cone 1. Never blew up though. The large scale industrial producers definitely have their process fine tuned. I got to tour a tile factory in Pennsylvania once, it was enlightening. Their clay body had a very high percentage of non plastic material, just enough clay to hold it together. It also had an exact percentage of water and was used in powder form. A measured amount of powder was dropped into a steel mold, pressed hydraulically, then popped out as a tile. From there it was on a conveyer under a glaze sprayer then into a tunnel kiln. Nothing ever stopped moving. 180° is a good temperature to candle at, you’ve just got to do it long enough to get the water out. Digital kiln controllers make this easier than it’s ever been in the history of ceramics. We live in good times.

Strongly agree with Bill’s post. Older elements take longer to heat than new ones, but then again a small kiln is less to heat. You’ll have to discover how long it takes your particular kiln to heat up. Definitely check to see if you can see a cone through that peep. By arranging the distance and height of the cone(s) you may be able to see it, or even part of it, through a small hole. No matter what you need some cones in there to check that the pyrometer is accurate. I had a similar kiln, tiny, three switches, low medium and high. I dried things out with the lid propped 1/2” and one switch on low for several hours. If it heats too much too fast, turn off the switch and shut the lid a couple hours then repeat. 210° F is the magical place things begin to explode. My experience is 180° for 6-8 hours keeps things from blowing up. It may be helpful to be familiar with the color to expect at various temperatures too.

You need: Proper orifice sizes for lpg and proper regulator for lpg.. Natural gas is “big” and low pressure, needs a big orifice and big pipes to deliver. Putting lpg through that must have been interesting. LPG is concentrated and has loads of pressure. Smaller orifice, more pressure, narrower pipes. Vince Pitelka has an orifice chart on his website. Ward burner is a font of wisdom in this department.

Seattle Pottery Supply says they have some talc as well. Now, this next bit is information not advice, because I’ve never made kiln shelves and don’t personally know anyone who has. Alumina and zircopax are both highly refractory, much more than talc. My experience (only to cone 6, mind you) is that zircopax sinters together significantly harder than alumina. My opinion is that I would rather chop existing kiln shelves into the shapes I need or buy them than to try and make them. That is, I suppose, because I now have more shelves than I need, and a day job. When I had no money, lots of time and lots of clay, making my own bricks to build a kiln worked out just fine. That was against the opinion of people more knowledgeable and experienced. People can have different opinions and both be right. As for advice I would say first to check if Michael Cardew had anything to say about making kiln shelves in his book “Pioneer Pottery.” You can take anything in there to the bank. Next, find a video of Isaac Button loading his kiln. He made his own shelves. Finally, take a look at Tony Hansen’s Digitalfire website. He’s made his own shelves too. Please let us know how things work out, I’d like to think we’re learning and teaching together here.

In my studio I use a jiffy mixer on a variable speed drill, if it’s splashing I slow down the drill. After it’s all stirred up I use a long whisk to make sure it’s in suspension, like if the bucket’s been sitting still for several minutes. At school it’s toilet brushes and big paint stir sticks. If there’s globs of glaze in the bristles students can see it’s not mixed up well enough. Mixing up new glazes I always sieve it couple times then adjust the viscosity with Epsom salts. That (Epsom salts) has probably saved me more time than anything else. I never have hard panned glazes. At worst it’s a thick gel at the bottom of the bucket, even after sitting a few months. Tony Hansen wrote a nice article on flocculating glazes and adjusting viscosity for anyone not familiar with that. I don’t go to the lengths he does for exactness, but just a basic understanding of the principles has been invaluable.

Students new to ceramics are learning a lot (hopefully!) to make sense of everything happening with this process. It kind of boggles my mind when I think about it. There’s really nothing in anyone’s ordinary experience to compare it to. After years of making pots so many things become second nature we don’t even think about them, but for students even the most basic things are like a new world. The beautiful thing is that it keeps getting better the more you learn. Decades on and I still make discoveries, still have surprises both to my delight and chagrin. I hope I never see the day I open a kiln and see everything looking exactly like I expected it to.

This sounds like a cool thing to explore, I can only guess what might happen. It may effloresce in different amounts on various parts of the work as it dries, which is an exciting thought. People into carbon trapping shinos use this property to great advantage. The other thing is that the soda will go into, not just on, your pot (I sense you already know this), so even if the foot is wiped clean I’d still either wad the work or make sure there’s a healthy coat of kiln wash on your shelves. Oh, and remember the stuff is caustic! That slippery feeling it leaves on your fingers is literally your skin being washed away. Use gloves and safety glasses. I’d love to know how the experiments come out.

I use local Anchorage clay, it’s considered a mediocre red earthenware here, no one really uses it. You’ve got to be discriminating when collecting to get the good plastic stuff and I add 1.5% veegum to help it play nice. Interestingly, at 04 it’s a bright orange, porous, but strong earthenware.. at 03 it is darker, completely vitreous (<1% absorption), and really strong. Like, I drop it on the floor and it bounces kind of strong. At cone 3-1/2 it’s a bloating slumpy mess. This is as opposed to the clay I got from Sheep Mountain a couple hours away. Threw like a dream right out of the bucket. Firing was a different story. Went from earthenware to ceramic foam in one cone. And I mean foam, frothy bubbling foam. Love the Rabbit holes.

It pulls water out of the clay just like plaster and doesn’t warp. I haven’t made bats out of it, so I can’t say much about that, but for ware boards it’s my favorite. The bottoms of pots dry more evenly in relation to the rims. As a work surface I wet it with a sponge to keep things from drying out too fast. I too would like to know if anyone has used this stuff for bats and what their experience was.

I love the stuff. I use 1/4” for ware boards. 1/2” is what covers my wedging table and works great for dewatering slop. Every bit as well as plaster. I did sand the surface of the 1/4” board, it’s kind of pebbly. Also, the 1/4” board gets saturated pretty fast, 1/2” is better for reclaim.

And here I thought I was the only one! I made several molds a few years ago, and still use them. They’re open ended cylinders made from slabs, then a bunch of holes cut into them. About 1/4 inch thick, maybe slightly thicker. Sturdy. Like you guys, I looked at pictures of antiques for direction. I usually make brie, but I did try them in a press a couple times with no problems. I will suggest taking care to make the holes big enough (1/8” drill bit worked well for me) and cleaning the glaze out of them before firing. I’m positive handmade ceramic molds make the cheese taste better.