Babs

So the grit you have washed out is from clay powder you bought? Might be essential for hand building and sculputural forms. On the other comments, cracking as shown when rolling is quite common. Rolling stretched the ribbing over really helps with my clay.

Btw if you are sieving and washing, you msy be throwing away the fine particles you require for plasticity

That cracking at edges when rolling shortish, i.e. low plasticity clay body, is common. Releasing clay between rolls, rolling in different directions, rolling in a gentle manner can alleviate this. From your wedged slab, cut a slice close to the thickness you require, the less handling the better imo. i.e. less stretched Clay may need to be a little wetter. Try rolling on a canvas. Just thoughts.

When did you buy your previous batch? Walkers did change sites of quarrying. But issues stated above re vitrifying and glaze maturity hold water if you'll pardon my poor choice of phrase

If your clay was my recycled,or like a tonneI bought behaving like yours, I would add " fines" which can get lost after throwing pots. @glazenerd has a magic solution, and or add bentonite. But it is hard to judge without hand on it. If the board you are working on is very absorbent, your clay may need to be wetter , or you could roll on a canvas or a cloth..... Areyou releasing the clay from the board during the rolling process. Compress that surface by running ribs on it. You plate mold should be coated with a releasing agent, green soap, oil sprayed. It looks like it has caught on the rim where it has cracked on left hand side. This would stress your whole pot. Your plate may need slow drying. It is shrinking quite a lot. As glazenerd wrote, change one thing at a time. I think you are closing in on this, keep testing. Don't prejudge on the "Masters " .they got where they are because they observe and test ad infinitum. Don't have to pick up all they say just what is relevant to you. All blinkers off in this game

You are overthinking this I feel. you have a clay body . It is not the best to work with. You add a temper to it, or temper it by adding the substance of your choice, or want to test,. this substance is the temper which can be a grog or any other substance you find helps you to work with the clay body. Ceramics is difficult enough without getting bogged down in the semantics imo.

Stilts will work best at low to midfiring temps imo , a little grind will remove rough spots.depending on design you can get away with just the end of underside of handle and a tiny area of belly of spoon being coated with resist and rest glazed.

If you are going to glaze those pieces, no , as those pots won't accept the glaze after reaching the glaze temperature. Those pots could be painted.... Also as greenware you would have to alter the start of your glaze firing. So use schedule for a bisque firing until 600 deg Çelcius then fire as usual for a glaze firing

That blue can be problematic. I used to mix a bit of frit into it, you'd have to test, as it doesn't meld with the glaze at certain thicknesses

You may have unevenly dried greenware at the point of application and so inadvertently getting thick areas where the clay grabs the moist underglaze.. I spray the whole pot with a light mist of water before starting to apply underglaze. It looks like you are brushing in lots of directions. Perhaps applying a resist to your flowers would enable you to then brush across your plates and get a more even application.

That purpling crystals are somethkng I get with a glaze containing Magnesium Catbonate. The effect of different fluxes I guess. The cobalt may have been thicker there where it is occurring on your dish. Metallic usually comes grom overload of the metallic element in the underglaze The bleeding is Bit thicker glaze? Glaze and so underglaze moving at that temp?

And a slow candling and slower ramps at start of bisque firing

Had a sculptural piece of an old friend's, sat around for years , still exploded, damp inside. Explosion...water, cracking , another story or two.

Yeh, I haven't witnessed that. Water would be out of it before glaze melt and sealed off escape routes? Test and see I guess

I have a glaze which likes to form bubbles when stirred and unless I spray hairspray to dispel them, or fettle them, they will affect the surface of the glaze but not going to the internal frothing of a lava glaze

OP firing to cone 6 with cone 7 half way down. CKay maturing at 1250 d C so not a low fire imo. @Anna M are your pots glazed all over? Which pots did not leak? Could weigh totally dry pot, soak totallly overnight and weigh to test absorbency %

Crack the dried clay down as much as possible snd then slake. Sand is your prob. If already a handbuiling clay ,dnt need it. Coil abit of clay and bend the coil around your finger, shouldn't crack.

The mold ,steel bowl , needs to be coated with something to prevent clay from sticking to it as it dries. Strips of damp newspaper, plastic wrap, green thick dishwashing liquid etc. Oh! a hump mold need to get that clay off there asap. Clay shrinks, mold doesn't How did you wet the clay down? Was the clay previously thrown into pots? Can lose fine particles which make clay plastic. Make a slurry of clay leave for a couple of days, spread out on plaster board to dry , wedge and see if it is better. May need some bentonite to increase plasticity. Do you know what clay it is?

I'd wait for your new bag of clay and when you get to glazing the new pots, put one of your unvitrified pots on a waster piece of clay, no need to pre bisque but could to feel safe. Put in hot spot in kiln The extra heatwork from refiring may nudge it over the line or may need to get that cone 7 over What glazes on pots which leaked ?variety or the higher maturing? Might save you an unsuccessful firing. Could put all on waster saucers and risk a melt and run of glazes. Would be a midfire clay which would be better I am sure.

What cone did you fire to? What cone does your glaze mature at? What does it say on your bag of clay re cone that clay requires for vitrification? Just that if glaze already on pot is a lowfire glaze and you need to go to a higher cone, your glaze may run off pot onto shelf. Re drying pot not necessary , justlike you can put pots just glazed straight into kiln for glaze firing.

Anoyher thing is if terra sig is pure then a bit of a stir , fine. If colourant added, need a big stir as syringe may be sucking more dense stuff from bottom.

What did your cones tell you? A bank of cones in line eith that spyhole would be handy. Cone 8 max so firing there continually will wear everything fast. What does the thermocouple look like. Just that, when freaking about my controller malfunctioning it was a simple slight bend in rod which hits the on lever when lid is closed, ok in lower range of temp but when everything heated it did not function properly.

Ok. Why not get any container, tare to zero with container on board. Add 100ml of whatever then move decimal point accordingly to get the SG...just saying

@Crooked Lawyer Potter You state you have tared the scale ,Dick's 1st question and then go on to take the weight of syringe off again in second part of your reply. If tare scale , don't then take weight of syringe off before x 2.. Or is this my misinterpretation?

How are you handling the coil as it leaves the extruder? Cutting in lengths required as it emerges or handling a long length. Could be your handling at that point of process, and your drying process. Are they small enough to hang within your kiln?