Just checking, and this may seem a dumb question but, there is supposed to be a small gap between the outside of the kiln and where the vent hose begins. Correct? I assumed it was for additional air intake but maybe I have this wrong?
Kilns both pass match test. I used a lighter and flame is pulled inward.
I'm not sure about that gap- I haven't used the Bailey vent. But if it's pulling flame then you're probably fine. All vents of that type need to pull a little air from the kiln, a lot more air from the room to cool it down in the ductwork. That gap may be providing the room air. You could try closing off a little bit of that gap to get more kiln draw. Sometimes vents can't keep up with the amount of fumes coming from wax burnout. You may want to consider putting in a secondary vent system, like through-the-wall fan, or an overhead hood.
I shoot for at least 10% clay in my glazes. They go on nicer, stay suspended better, and aren't so powdery when loading the kiln. I've got some glaze that have over 20% clay, and they are a delight to apply. They go on smooth, and are tough as nails when handling them.
Very cool, but likely very expensive to run. It takes a lot of electricity to create heat, as we all know from running our kilns. You've got 2000 watts running, so 48kwh per day. I pay 17 cents per kwh, so that would cost me more than $8 per day. Over a month that's $245 to heat a 560 square foot space. It would be cheaper in the long run to put in a hanging gas heater. I heat my 1200 square foot studio for $77 a month on budget billing, so figure $150 at most during the cold months.
I make sinks a lot thicker than I would a normal bowl of that size, so it's less likely to warp in the firing and less likely to break if someone drops a cup in it. So for a standard 16" sink, which has to be thrown to almost 19", I use 17 pounds of clay. I make them as a vessel (sit on top of the counter), or as a drop-in with a flared rim. I leave a thick ring, like a second foot ring, around the drain hole so there's a good solid area to tighten up the drain assembly. I also trim a recess around the drain hole on the inside so the drain flange sits low so all the water drains out.
Here's an easy way to make deflocculated slip without having to measure out a bunch of stuff: Completely dry out a bunch of your clay body. Break it into pieces. They don't have to be really small. Then put it in a container and fill it with water until it covers the clay. Let it sit overnight. The clay will slake down into mush at the bottom of the container. Do not stir it! Carefully pour off all the water on top. What you have left will be a very thick slip. Add sodium silicate by drops while mixing smooth with a stick blender until you get the consistency you want.
Standard 551 does not feel anything like a typical grolleg porcelain. It feels like it has a bunch of ball clay in it. It is overly-plastic for a porcelain, and feels more like a white stoneware. If you like the non-plastic feel of a typical grolleg porcelain, you may not like the 551.
You can mix clay bodies as long as they are formulated to mature at the same temp.
OK, got me, poor example there . How about the bowl example?
I don't think you're necessarily wrong about that being memory. I think the same phenomenon is in effect either way. Whether in a narrow spout or a wide bowl or rolling a slab, the platelets are being aligned in a certain way during the making, and during firing they tighten up. In the case of a narrow spout it causes twisting, which probably happens in all thrown forms to some degree, it's just not noticeable in a wider piece, nor is it very noticeable in a spout that hasn't had the lip cut at an angle. In a bowl or slab that has been altered, as they tighten up they try pull the shape back to the original configuration. When you alter a piece, the platelets are no longer aligned in a way that agrees with the form. In the case of a squared bowl, they platelets were aligned to make that specific round form, not a square form. I tend to think of it as returning to a state of equilibrium, where the particles are happy, kind of like a slinky returning to its closed position.
The matte glaze may have cooled too quickly, or it was over-fired. As for the iron, it looks exactly as I would expect under a glaze. The iron is taken into the glaze and diluted. You can see the dark areas where it's going black, which is where the iron is on thicker. It takes a lot of iron to go dark under a glaze when firing in oxidation. I used to use a 10% iron slip in reduction, I use a 22% iron slip in oxidation to get the same darkness. Personally, I would use an iron slip rather than straight iron. It's easier to get an even application, and won't go metallic and overload the glaze when thick.
One of the easiest things to notice in the way of memory is a thrown teapot spout that has been cut at an angle to match the top rim of the teapot. If the wheel is going in a counter-clockwise manner, the spout will when fired-unwind slightly in a clockwise motion, there for the angle of the cut needs to be slightly to the right 3-5 degrees for the cut to be parallel with the rim.
Other instance of this would be a bowl that has been thrown thinly, and later when cheese hard gets warped lightly. When fired it comes out the way it had been originally.
Instance of this memory are something that as you work with the clay, and notice changes is firing, and evaluate those changes that you are able to make conclusions about memory, firing cycles, assembly techniques and other things about the clay. A lot of what we do out there is intuition, and without apparent thought even though years ago we had an AHA moment that became innate and basically a priori knowledge that we act on without thinking.
Actually, the spout continues to twist in the direction of the torque, clockwise as you look into the spout.
Memory is not an issue for most wheel thrown forms, mostly just for those long narrow things like spouts. It has to do with the alignment of the clay platelets. You can trim the outside of a pot totally smooth, then the throwing rings come back after firing because the pressure of your fingers aligns the platelets in a certain way during throwing. So you have to smooth the pot during throwing rather than trimming it smooth.