Pyewackette

If it's a throwing class, why are they taking more students than wheels? The mixed levels is not a problem at all. Every class I've ever taken or taught  has been mixed levels. I think it's great, because the advanced students pass a lot of knowledge down to the beginners. But for the class to really work well you need everyone to have a wheel.

Our local art museum would have a exhibit for children with impaired sight,   they could pick up and touch the art work.   I  thought it would be great if they had  a permanent exhibit for all children to enjoy touching the art work.   I would be happy to donate pots to it.     I love to observe  and touch  pottery,  it gives me a feeling of being grounded to the earth.    Denice

Much of my work I make while "blind" (voluntarily-I am sighted) so that the tactile experience comes to the forefront and the piece can have an delibertly expressive  "feel" regardless of whether or not anyone can see the coloration.
 
 

As we have been drawn to working with our hands and clay i'd say our haptic sense is heightened. Certain pots will attract us, cupboard full of similar mugs, we'll find a favourite and seek it out.
Potting with eyes closed when centering and  pulling up clay can make our haptic sense reveal itself also.
It is cruel to go to an exhibition and be forbidden to pick up and touch the pots.
 

Some raw materials are increasing more than others. All of them are increasing. Watch lithium bearing materials like spodumene and hectorite. Crazy. That means any premixed glaze will cost more. Different suppliers have different prices because they buy In quantity, sometimes they buy a ton of something well in advance and can make a profit selling it lower than market price. Do some shopping, it’s a temporary fix. Everything is going up.
Avoid buying water (liquid glaze), add your own. 

Your right people who wander into my studio would be thrilled if I gave them a pot.   But they aren't so thrilled when you give them a price.    Denice

The clay suppliers cannot control the quality of their raw materials, nor can they test each bag of raw materials, nor can they really inspect every batch of clay to find chunks in it, especially if the chunks not a certain percentage of the mix. It would be impossible to find them. They rely on their raw materials suppliers to provide quality materials, and they take a risk with every batch of clay they make. But it's they're job to acknowledge that there's a problem and make it right, either through refund or replacement, just like the raw materials suppliers will have to do for them. That's all they can do- be nice about it and make it right. If they can't do that, I would consider finding another supplier (I know that's not a simple thing). Clay is cheap, even when it's expensive, and replacing one ton isn't going to hurt their bottom line at all when they're selling a few million pounds a year.
I used to run the clay production lines at A.R.T. clay, and if we found a problem that was not the fault of the potter, we would replace the clay body. One person who bought 100 pounds and had a problem is probably not the clay's fault. Several reports from different studios is probably a clay problem. Chunks of rock would definitely fall into the replacement category, regardless of how many people found it. We once found a hole in the stainless steel liner of our mixer, meaning there was a quarter-sized piece of metal (or several smaller pieces) somewhere in the clay. Bad news. We had to throw out all the clay we had mixed since we last cleaned out the mixer completely and knew there wasn't a hole in it, something like 12,000 pounds.

He’s saying oxides for simplicity’s sake, but his copper wash is the carbonate form. Copper oxide is usually black or red. 
 
Short answer is price, and because the base glaze plays a part in fuming as well. Some base glazes will release or pick up things better than others. They’re useful in different applications.
In some instances fuming may be desired. Some soda firers will place small cups of copper or cobalt at points in the kiln so it flashes onto the adjacent pots. They use the oxide or carbonate form because it’s less toxic than the salts, and having it contained in the kiln is less hazardous than applying it with a spray bottle post raku kiln. Still wants to wear your respirator though. 
As mentioned in the digitalfire articles, carbonates disperse differently in glazes than oxides do. Cobalt oxide, unless ground very finely or put through a 100mesh sieve, tends to leave specks in a glaze, while carbonate disperses quite neatly. But the light purple colour of carbonate can be hard to see if you’re using it for brushwork, so the oxide is a better choice for that.
For copper carbonate, in high fire glazes it doesn’t usually give too many people grief. But the pinholing at cone 6 is a right nuisance, so some people are starting to use the oxide instead. 

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.

I slice and slam my bags of recycle often with part of a freshly opened bag. I use a wiggle wire to do this, and spray water between layers. After cutting through the blocks once to combine I slam and re-block to cut from another direction until all sides have been cut and slammed. Then the clay gets wedged using the cone method. I started doing the same as her putting the point down when I found that large plates would seem to survive better in that manner.  My biggest complaint of the video. . .  as much as she explains the process and demonstrates it well, her wedging table is very inefficient!   The table should be lower so that the wedging motion uses more of the shoulder and body to move the clay. When I wedge, the motion of the wedging lifts the shoulders and stretches the spine. . . that is why I have said so often that I wedging relieves the pain in my back. The rocking and stretching helps a lot, especially on days when the weather change causes those old aches from old injuries to flair up.
IMHO
 
best,
Pres

@PyewacketteYup, you are doing it right already. When the wedged roll is sitting on its side lengthwise in front of you, standing it up clockwise is tilting it to the right. As for the stacking direction during the wire and stack, the only thing that matters IMO is keeping the layers of each half stacked parallel to the table. The concept is doubling the number of layers with each stack, and squishing them down to half their thickness from the previous stack. When showing the students, I keep a running count of the number of layers - 1 (the original block), 2, 4, 8, etc. Ten cuts and stacks yields 1,024 layers, each 1/1024 the thickness of the original block, intermixed so thoroughly you can't tell where any "lump" or dry or wet area from the original block is anymore. Ten more cuts and stacks puts you at over 1 million mixed layers. With the students, I usually start with one chunk of light clay and one of dark clay. Each cut I show them the colored striations of the layers, until somewhere around 15 cuts, it is totally uniform and there are no more stripes of color. As for orientation of rotation, I don't consciously worry. I have a very rhythmic lift of the block through the wire, and then rotate one wrist to slap that piece down upside down from its position when I pulled it up through the wire, and then immediately rotate the other wrist to slap that half down on top of the first piece. Twang whack whack. Twang whack whack.

I have never seen the direction of the wedging to have any effect on my throwing or any of my students' throwing. Once you cone the clay a couple of times during centering, any wedging spiral is gone. IMO she is overthinking the process, or finding something to blame for poor centering technique. I have wedged 'backwards' of the way she's showing for 30 years, and I've never had any issues. Same with my students. Wedge it, make it into a ball, smack it onto the wheelhead, and center it. With good coning technique it doesn't matter which way it was wedged.

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.
 

I was thinking he meant unholy bats like of the vampire persuasion ... and yes, I frequently overthink things LOL! (Yolks on me)

That is the method I was taught to wedge clay.   Denice

In many many years, I have never found proof that one can polarize or directionally align reasonably wedged clay. I have not found that to be credible in my experience.

You will love it! I had a friend make this simple metal base (it's what he had for free) w/a wire attached and it has saved my wrists and made prepping clay so much less of a chore!

Yes, I too mostly wire and stack, it is more efficient and more effective at redistributing the uneveness of any clay that either just came out of the bag or has been sitting around longer than an hour or two. I always finish with a quick few times around of ram's head wedging, mostly just to make the squarish chunk round - it throws better when it is round... The ram's head method is more or less symmetrical  left and right, as opposed to the spiral method. After ram's head wedging it, I turn it to the left and stand it on end, rounding the end a bit to roll out any air pockets. Then it is ready to throw on the clockwise wheel, with the spiral from the ram's head rotating in the proper direction to tighten the spiral. For you, Pye, you are already doing all of this up to the very last step. Instead of turning the ram's head to the left, you turn it to the right and the spiral will be oriented properly for you throwing on a clockwise wheel.

A sheet of 220 wet dry sandpaper usually takes care of most residuals, if you’re only using clay with a manganese speckle.
While the piece is still leather hard, it can also help to give the contact points a polish with the little red rib, and make sure the bat you put the piece on to dry has no crumbs that will push into the foot. I hate sanding, so I try to opt for prevention rather than cure.

Take your claybody that the pots are made with and run it through a 60 mesh screen to remove most of the grog / sand. Brush that onto the feet of the groggy clay pots. After glaze firing rub the foot over with a diamond sanding pad.

Glaze the foot ring, and then sit the centre, unlgazed part of the pot on a kiln post to raise it off the shelf.

Good questions.
I don't have answers, will share an observation: the tin-chrome red glaze I'm using* picks up blue flecks, I'm guessing from neighboring pots, however, some of the flecking could have been from the kiln**.
Sometimes there's more blue flecks on surfaces facing upward-ish, sometimes more on one side than the others...
My glaze loads typically have a lot of blue in thar, a semi-transparent blue, a variegated blue (with rutile), and a light blue; all use cobalt carbonate.
 
*got the recipe from local JC ceramic lab (matches "Chrome Red" from John Britt's book)
**my guess is that the same will happen in my brand-new kiln, tbd.
The old kiln had seen almost thirty years of service before it came to me! The prior owner definitely used blue glazes...

I recently started using my bat pins and much prefer them. Wish I’d done it sooner!

@Rae Reich I'm a super dry thrower - I often leave NO water at all in the splash pan.  In fact of late I prefer not to use a splash pan at all except for trimming - because without it, trimmings fly all over the place.  Otherwise the splash pan just gets in my way.  I really am the driest thrower I've ever seen, to the point where I have to kind of check myself and use MORE water than I'm first inclined to use.
I also usually only use sponges to move water, either in or out.  Lots of people seem to throw with sponges in their hand - I'm not one of them.  And I've gotten MUCH better at having even walls, something I struggled with until we got these new clay bodies and I could stop using the perpetually short studio clay body they make here.
However I still feel like I'm pretty slow.  Maybe that's part of it.  Also the form I've been favoring for awhile now is a flared out shallow bowl with very straight sides.  It's pretty gravity defying to start with.  However however I am also struggling with vase shapes in the 3 to 4 lb range.  
Possibly I also need to experience some success with these forms in another clay body as I've made a medium sized bowl as described in one of the new stonewares at the studio (but I only had a bowl sized sample of that available).  I keep hoping the new stonewares will arrive soon, so far it is always "next week".  This week's next week hasn't happened yet either LOL!
I'm faster now but it isn't anything I would actually call "fast" - I am not doing a John Britt 6 bowls in 3 minutes thing by a long shot.  So possibly I've just got my hands on the clay too long, still.
Frankly I was shocked I could throw in porcelain at all, given how I've struggled with the studio clay over the past 2 or 3 years.  I about gave up hope.
I've seen people on youtube using heat guns on porcelain forms in the size range I'm attempting.  I'm really not a heat gun fan but thought maybe I was being too intransigent on this issue in the case of porcelain.  I'll keep trying - sans heat guns.
Thanks.

@Min Sorry I meant the DiamondCore Sticky Bat. Those things are SPENDY!!!! I have my own versions of the Bat Mate.  One is made using that waffled shelf liner, it works fine for Speedball plastic bats to stop clatter and wobble.  The other is made out of Sham Chamois used for wiping down cars.  You wet it, wring it out, and it helps with slightly warped wooden/masonite bats or those solid plastic bats (not Speedballs, they have hollows underneath). It also gives it just a little bit of an underhang to get hold of and pull the bat off when you're done.
I always use bat pins.  Having to center the clay is quite enough centering while I'm throwing LOL!
3mm - that's less than an eighth of an inch!  I guess I'd better rethink that 1/2" neoprene roll I was thinking of getting LOL!
Thanks.