Kelly in AK

Kiln wash has a tendency to flake off, better put, kiln wash WILL flake off sooner or later. In an atmospheric kiln there’s lots of airflow so loose bits of wash on shelves can easily blow into pots and ruin them. Add fluxes flying through the kiln (ash, sodium) and it’s more complicated. Every firing changes the coefficient of expansion of the surface, a little flux gets absorbed, a little more heat work gets done, the coating shrinks a tiny bit more than it did before. Placed on walls, roofs, or the underside of shelves is a guarantee of having flakes of kiln wash stuck to pots. Coating walls is less problematic, but still carries some risk. In that case a coating that’s formulated to stick very well is necessary and that’s no mean feat. Hard brick wood, soda, and salt kilns are often coated with a spray of shino glaze which creates a protective barrier for the bricks.

The CMW clay profiles website is very cool. You do have to make an account to view, but it’s free of charge. I really appreciate them making it freely available, lots of work went into producing that data. Now, to a fun point. I like to dog on any clay that’s billed as cone 6-10, because there’s always an element of misrepresentation there. Someone is trying to sell clay to the widest audience possible, miracle clay, can do it all. And there ain’t no such thing. So I thought. To my surprise, there are a couple that come pretty close. Continental Clay Company’s buff stoneware and Standard’s 259. So when you think of the range a clay can fire in and be considered vitreous enough for tableware these are interesting. Of course there are a lot of other things we expect our clay to do, like be plastic but not crack, and fit the glazes we like, and look how we want it to look. So I’m probably not done dogging on the idea of cone 6-10 clay yet, but maybe have to be a little more careful with my pronouncements!

Shiny! Congratulations.

Oh you may be surprised how things change when you have your own kiln. The only advice I have, which you’re already accounting for, is to buy a brand you can get parts for easily. I have two electric kilns in my classroom, different brands, both well known. One is easier and less expensive to service than the other. (I’m not trying to be coy here, I just don’t have enough experience to comfortably recommend a specific brand. It could be that I’m just bad at shopping for kiln parts.)

This, from @JohnnyK might be helpful-

In case someone reading the thread becomes so intrigued with Black 4.0 they simply must order it, I feel obliged to make a little public service announcement. I ordered some about two and a half months ago (May 7). It’s not here yet. I waited till the two month mark to email them and got an auto generated response apologizing for the wait and informing me that I was near the “top of the queue.” Poking around the web a bit I see this is a common experience. So, be prepared to wait, I guess.

I can’t directly address your question, but have some information that may be helpful. I have a little bit of experience with zircon kiln wash, but haven’t used it much as just plain kiln wash. That is, I came into possession of a bunch of zircopax by virtue of buying someone’s raw material supply when they retired. There was no alumina in the lot. I built a soda/wood kiln with mostly soft brick from cast off electric kilns. I dipped the hot face of these in a wash of roughly 70/30 zircopax/kaolin. I’ve done that for the following two rebuilds of the kiln (new brick, k-26, and now the walls are lined with thin kiln shelves). No coating I know of will keep the bricks from spalling, but this one does extend their life. I extrapolate that from how quickly soda decimates places where the coating has come off. It doesn’t flake or peel easily and fires harder than kaolin/alumina wash. Since I had no alumina I also used zircopax/kaolin for wadding and shelf wash the first couple firings. The wash was fine. Wads not so much. They were very hard and not easy to get off the pots. I wouldn’t do it again. It really showed me how different an animal zircon is from alumina. This is at cone 6-7. I use a mix of 60/40 alumina/kaolin now for shelf wash. Silicon carbide shelves. It doesn’t curl or flake, but I put it on thin and scrape the shelves every firing so it never builds up. For wadding it’s the same but I add some flour to make it easier to shape.

Around 30 years ago I went to the American Craft Council show in Baltimore. I was in graduate school and it was practically right down the street (in Alaska, that means less than a two hour drive). I was blown away by the size of the show and quality of work. I didn’t love every booth, but it was packed with the largest collection of high quality handmade goods I’ve ever seen. I haven’t been a show that’s matched it since. I bought a couple cups I couldn’t afford and use them to this day. Around 10 years ago I went to a juried art/craft fair in Park City, Utah. That was a good one, not the scale of the ACC show, but quality stuff. It was a mix of painters, sculptors, and craftspeople. I really enjoy seeing the creative ways people display their work and cope with the challenges a craft show presents.

A different type of juried/themed show can be very helpful. That is a show that is all potters. Some of my biggest weeks have come from that environment. A craft show, not an exhibit, but all pottery.

I found no reason for Venmo after using Square. One more hassle I didn’t need. Square’s too easy. I have Venmo, very rarely have need for it.

I find this a wonderful question. BMix-5, which I use regularly is described as 2.3% absorption at cone 5. It is absolutely tighter at cone 6, where I fire it. If cone 7 is down it wil start slumping. I believe different bodies have different functional ranges. My local clay goes from porous to vitrified to slumping in a cone and a half. (04- porous, 03- vitreous, 02 tipping - slumping, followed shortly thereafter by bloating.

Gray area for some of us old schoolers. I stick with < 1.5% as solidly safe. I was taught (30 years ago) anything under 3% is passable but less than ideal. That’s where the leaks begin to show. Under 2% wont leak. Over the years popular opinion has reduced these numbers, probably creating stronger more reliable ware.<1% is a more common goal for most people now. Glaze fit has developed in tandem in the modern craft potters’ craft which skews results a bit. A well fitting glaze can strengthen and protect a pot that is not fully vitrified for years. I have some mass produced diner plates that are proof. Firing a cone higher (or a soak) can sometimes get you the absorption level you want without destroying the glazes.

I’ve made lots of terra sig, from redart and several other clays. I’ve never used, or felt the need for, a ball mill. If I were adding Mason stains I would use one. You’re keeping only the finest particle size fraction of the clay, accept that you’ll be throwing out the rest. It feels weird at first. Trying to squeeze out “a little more” from the dregs is a false economy. Some clays work better than others. Redart and OM4 work great. Lincoln 60 works good. The kaolins I tried were not so great, low yield. The maturing temperature of the clay you make it from affects the fired surface. For example redart will be very hard and satiny at cone 04. Terra sig from OM4 will look a lot the same at 04 as it does green, a little whiter, but also easily scratched, soft. Too many variables to go on about it, just be aware different clays have different properties and making them into terra sig doesn’t radically change those. Yes it works on stoneware. The important thing to know is to apply in thin layers, whatever you’re putting it on. It’s not going to be like slip, it needs to be more like 2% milk. Thin. You can build it up with successive coats. Buffing them with a plastic bag is a nice trick.

Inspired by this thread and the article it links to, I built it. https://community.ceramicartsdaily.org/topic/41994-best-handheld-extruder-for-feet-for-large-pots/ Not counting the trip to the hardware store it took about 15 minutes (I have tools, which is an advantage). It gave me an 11 foot coil that was 3/8” in diameter. I didn’t have to make up some extra soft clay, it’s easy to use and clean, and fast. Brilliant @Pres. The dies are washers pressed into “test caps.” Note well: The plunger has to be sanded down a bit to fit into the 1-1/2” pvc pipe.

I can tell so much more about a pot by looking and handling it than I could 20 years ago. Five years ago, for that matter. Yes, my perception has definitely changed. I appreciate some things much more than I used to. A few things, very few, I appreciate less. I think that’s like when you learn how a magician does a trick and realize it’s really much simpler than you imagined. Then again, sometimes when you learn how it’s done that makes it even better. People say pots tell a story, those stories are mostly fuller and more interesting for me now than they used to be.

Oh dang. Looks like I’m getting another power tool. Great article @Pres & @Min!

This has been my experience too. I made one from a caulking gun and pvc pipe, it only works with the softest clay and still difficult to sqeeze. I have a wall mounted one, but I don’t use it. Too large and unwieldy, I don’t extrude enough to justify the bother. I’m intrigued by the “electric assist” described by @Pres and @Dick White! I do use this thing. Love it. The handle creates enough leverage to make it easy. Unfortunately I don’t know what it was originally made for and I can’t even remember where I got it. I think it was some surplus geological or engineering testing equipment, it wasn’t from a ceramic supplier.

Kaolin, probably, but I’m afraid it’s not that simple. As @Bill Kielb said, if there’s a recipe people could make reasonably reliable suggestions. If it’s a pre-mixed commercial glaze perhaps you could ask the supplier exactly what you asked here. I haven’t got a clue what kind of response you’d get but it can’t hurt to ask. Adding something, kaolin, for example, changes the percentage of all other ingredients and there’s no telling what effects it may have beyond making the glaze stiffer.

You’ll be glad you insulated it. Depending on the square footage, it may take very little to keep it above freezing, a small space heater. Un-insulated will take a lot of energy to keep it above freezing, let alone warm. Water turning solid wreaks all kind of havoc and you will waste lots of time and energy just dealing with it. I’ve done both ways, poor insulation leads to spending too much time mitigating the cold and robs you of time you could be spending making work. Rustic is charming, but time is limited. Another thing worth doing is skirting it. That makes the space under the shed an insulated cushion, much better than just insulating the floor.

A temperature correlation to a cone is dependent on the rate of temperature rise, very important distinction!

The Gerstley is pretty clay like, I can imagine it’s a tougher unfired surface. The CMC will get harder the drier it is, propylene glycol slows the drying down, maybe that’s a thing. Ron Meyer’s Clear is a glaze with lots of frit and only 10% kaolin, but it’s also got 2% bentonite, and that improves green strength (as well as keeping glaze in suspension).

I use some from Clay Art Center in Tacoma in my classroom, have for years without trouble. Let’s see, the favorites are: PZN clear (can be used as a base too, add stains or oxides), Sagebrush Celadon, Plum Red, Floating Blue, and Cola Green. The last three are sensitive to thickness and give different color responses. Caribbean is a nice one too.

Of all those glazes only indigo float looks like it doesn’t have a green tendency in it. The others vary with thickness. Certainly the clay underneath will affect the color. The speed of firing will also affect it, sometimes significantly. Using physical cones will help you know what’s really going on in the kiln. If your kiln is plodding along at 60°C/hour for the final hundred degrees, then 1250°C is cone 8.

Well something has changed, we’ve got to figure out what. Is it possible the clay body formula has changed? In the recent past many clay companies have reformulated certain bodies due to material shortages (mostly talc, I understand). It may be worth asking your supplier if you’re not sure. Another thought is that maybe your slip has changed. I get the impression you mix it yourself, have you gotten any new batches of material? Perhaps one of those is different. Made any substitutions? I hate to say it, but since we’ve all done this, it could even be a measurement error when you were compounding the slip recipe. All is not lost. Something has to be adjusted. If you post the name of the clay body and slip recipe there’s a fair chance people here could help you sleuth that out.

It seems your clay is quite refractory, but reducing the (assumed) calcium content will be a chore. As @Jeff Longtin said, mixing it with a lot of water and discarding the dregs could help. The larger particles and non plastics will settle out first. Takes patience. Another thought is to find a cleaner seam of material to pick. I read a field test for calcium is to put drops of vinegar or muriatic acid on the clay and see if it fizzes. This is also a fun read: https://digitalfire.com/material/limestone I’m curious to know how your fired samples behave submerged in water.