Hulk

All right.  For an initial test I have mixed up about 1/3 cup white earthenware slip (cone 06-04 that I got locally and ball milled it a few days) and to this I added about a tablespoon of vinegar.  Mixed it up and it bubbled a little bit (a lot of the recipes mention vinegar but not sure why exactly).  By morning it had settled on top as a clear fluid and the slip had become rather unplastic, sort of more like wet sand than slip.  I poured off the excess fluid.
Then I added about 1/2 a teaspoon soda ash and mixed it in well.  It tried to form a hard crust so I had to put it into one of my mortars and use the pestle to grind it smooth again.  I have a rather large ball mill but alas, not a little one.  Maybe I should make myself a smaller porcelain jar and little balls for just such things ... but I digress!
The last thing I added was 1 ml of sodium silicate, mixed well then a touch more.  It became very creamy and lost the hint of grittiness.  I have no idea how it will preform but now I'm going to test it.  Not sure if the vinegar was actually any help at all or not but the soda ash and sodium silicate made sense.  I'll let you know how well it works or doesn't.  I'm going to test it filling in tiny defects and a crack in a bone china horse sculpture I want to glaze.  My initial reaction is it has a good feel, much like the bisque mender I had been using and loved.
I can always color adjust afterwards with a little airbrushed opaque white underglaze if needed over it to blend it in before I move onto coloring the piece.  Wish me luck!  I'll be firing it to cone 04.
 

I have been spending a lot of time and energy replacing my Gerstley Borate glazes. The new ones are coming along, but they just don’t have the same glow and magic. I am trying to push the limits of “how much boron can I get away with?”
The good news is that switching to Fabi Talc in place of Texas Talc has been seamless. 

I've had to reformulate over half of our pottery glazes, both cone 6 and cone 10 to accommodate the end of Gerstley Borate, Custer, and Texas Talc. Using frits for GB, Mahavir Potash Feldspar for Custer, and dolomite/whiting for talc. Of course, all of the recipes needed changes to amounts of silica, kaolin, etc.
The tough ones seem to be the recipes that were "breaking" glazes or used some sort of lithium. Those took some tweaking and testing to get to a similar match to the old glazes.
Our local supplier has switched from Custer to G-200EU in their clay body mixes without any noticeable difference.

The clays I like from "nearby" vendor (about a hundred miles) have been reformulated.
The whitish stoneware seems about the same, the red behaves a bit differently.
My intent was (still is!) to look into alternatives this year; I've enough Gerstley, Custer, and Texas Talc to last a few years, however, years go quickly...

The clays I like from "nearby" vendor (about a hundred miles) have been reformulated.
The whitish stoneware seems about the same, the red behaves a bit differently.
My intent was (still is!) to look into alternatives this year; I've enough Gerstley, Custer, and Texas Talc to last a few years, however, years go quickly...

I have a favorite glaze that uses talc, and up until lately have had quite a bit to use in glazes that I bought several years ago. However this last glaze batch found me with none left. Last year I had heard about  a shortage of talc, and believed I would have to reformulate my glaze to work with a different component, maybe dolomite. Imagine my surprise when I found Fabi Talc listed at SC. So I will be ordering some to use in my glaze. However, it makes me wonder if anyone has had to reformulate glazes or clay bodies due to a lack of materials? 
QotW: Have you had to reformulate any clays or glazes due to a shortage of materials?
 
best,
Pres

All the time now. Gerstley is gone and Gillespie is not a perfect match. 3134 requires a complete rewrite of the recipe. Custer is gone from the market, but I still have some. G200EU might be ok, haven’t tried it yet. Still have some old Amtal talc, but some Fabi is in my future. What’s next?

It’s a good question. People end up finding their absorption happy place, some are unsatisfied with anything over 1%, others with 0.5%, I am good if the mugs don’t weep or get wickedly hot in the microwave. I believe that’s below 2%. The ASTM standard for vitrified is 0.5%.
My understanding is similar to yours, about firing range. I could be wrong about this, but my general observation is the lower the maturation temperature of the clay, the narrower the firing range. It’s certain the closer you get to vitreous the less wiggle room you have, at any cone. 
In his book Clay and Glazes for the Potter, Daniel Rhodes says, “Fired stoneware should have an absorption of 3 percent or less.” That’s on page 42 of my edition. I was taught, a few decades ago, that absorption below 2% makes reliable pottery but you should shoot for below 1.5%. Talking to potters over the years gives me the impression that the desired number has crept down since Daniel Rhodes wrote his book. 
Now, back to low fire, is it suitable for everyday use? Not without some careful consideration. There are a lot of variables, so many it seems like a subjective question. It depends on what you’re willing to put up with, or what you’re asking of people who use your pots. I use a lot of earthenware in my kitchen, I wouldn’t expect someone buying my work to deal with that, so I don’t sell anything unless it’s non-absorbent. The issues are strength, absorption, and glaze fit (which really goes back to the first two). The solutions are finding/making a clay body that works and then glazes that fit it. 

Looks like Lemon Grove is in southern CA, near the Mexico border.  (If you google it you can actually see the storefront.)
It appears to be located near a place called Plaster City. (A site producing plaster for USG.)
Imagine setting up a mold making studio in Plaster City?

When looking for glaze recipes (cone 5/6), I chose from sources that included notes (results, application, and test results an extra plus!).
If starting over, would definitely consider refining a (one, just one!) base glaze first, then coloring it.

For example,
This Forum
digitalfire.com
John Hesselberth's FrogpondPottery.com* (There are three low fire glaze recipes, with notes).
Susan Peterson's book The Craft and Art of Clay
Lakeside Pottery's website includes some glaze recipes**
Another book I'm not remembering just now, will look for it ...not finding it, will try again later
Bill van Gilder's book (I use two or three from his book) Wheel-Thrown Pottery
I was looking for recipes from a known source, where there are usage and/or testing notes included (pictures are nice too)
A well behaved clear liner (there's enough white in mine to show over dark clays) glaze took some time, testing, trial, start-overs, some help, and then aaah. 
It has significant MgO, small amounts of Sodium and Potassium, a dose of Lithium (a little bit makes a difference!), and there's Boron - it melts well - for I work cone 5/6; there's enough Silica and Alumina to make a tough glaze that doesn't run or sag much.
*archived here Tested Glazes | Frog Pond Pottery (archive.org)
**Cone 6 Glaze Recipes | Great Mid Range Pottery Glazes (lakesidepottery.com)

Hi and welcome!
It is possible to get durable ware at earthenware, midfire and high fire temperatures, but there are different considerations at each of those points. I won’t use the term food safe, because it’s a bit of a misnomer, and legally only covers whether or not the glaze has cadmium or lead in it. When we talk about glaze durability, we want to make sure that the clay is fired to a point where it would have less than 1% absorbion, the glaze doesn’t leach anything, isn’t crazed, resists both scratching and cutlery marking, and is easy to clean. 
With earthenware in particular, you have to be mindful of glaze fit, because earthenware clay remains porous when fired to maturity, and many will glaze the piece all over, and use kiln stilts instead of leaving a bare foot. You have to be extra mindful of your glaze chemistry, because the low temperatures tend to mean the fun, pretty glazes can sometimes be prone to scratching because they’re lower in silica and alumina.

I just realized that I never came back to reply, and it's super irritating when people do that...
Anyways, I tried working faster and stirring more vigorously, and the plaster set up as usual. Success!
I didn't know that faster stirring made for stronger plaster, so I'll get out the jiffy mixer next time. (I learned to mix plaster in a community college class, so we might have been stirring by hand because it was more practical for a group of people than taking turns with a jiffy mixer.)
Thanks, all, I really appreciate the advice.

Damn @neilestrick!!!
Best low fire work I’ve seen in a long time. So good I could eat it.
To @Biglou13, bisque anything will tolerate that kind of abuse better than a clay close to maturity. Lots of grog, kyanite, or even spodumene (gotten a bit expensive lately) will help. Unglazed flameware sounds better than any other clay body, but I haven’t tried that.
It can be done in the studio, ordinary clay products that handle the extreme temperature swings of cooking, but that’s far from saying it should be. I’ve made several earthenware pots that survive the stovetop, experimenting with clay formulations and bisque temperatures. Though I used them regularly, the maintenance was unforgiving (mold will not be denied if given a habitat to grow), and sooner or later they will fall apart despite all best practices. You didn’t bring this up, but I would never try to sell such a thing. Too complicated. 
Pottery used for cooking is largely disposable, in places it’s actually used. Manufacturers like Le Creuset and Wiliams-Sonoma create ceramic ware that’s functional in a contemporary kitchen, but they are carefully engineered first world conveniences. If people can afford to use metal they do. 
I’ll confess, I’ve never had better beans than those I cooked in clay pots. I don’t want to discourage anybody, I just think they should know what they’re in for. 

@Biglou13I started seriously making sourdough bread 6 weeks ago. Sooooo much fun.  I took a class and learned what I had been doing wrong!  I use cast iron skillets, aka dutch oven.  I would recommend that as well.  

Hi @Biglou13 A flameware body would be your best bet for this. 500F is pretty hot for a clay dish, especially since you'll be dropping wet, room temp dough onto a hot, flat surface. It's a lot to ask of any clay body besides flameware. The other option is to just buy a cheap cast iron dutch oven on Amazon. It works great, and you don't have to worry about it cracking. My dutch oven is preheating in my oven as I type this! 
My loaf from last week. 25% whole wheat, 80% hydration:

https://www.desertcart.ae/products/425093753
This is the clay I am using.
around 1hr and a half to cool dowm

That's a steam explosion from firing too fast for the thickness of the piece, or the piece still being too wet. Let the piece dry completely, do a preheat for a couple hours. Be sure to vacuum out all the clay crumbs from the elements.

Here is the completed piece all glazed up.  All work has been done in the kiln, completed with satin glaze and minimal china painting.  The only thing on him that isn't ceramic media are his mane flights which are enameled metal, inset with pins into tiny holes along his neck.  Completed to a light dappled grey and with an optional base I have made for him to be affixed to, this piece will be posted to public auction.  He measures 3.75" inches tall and will be a unique color and variety in an edition of not more than probably 20 or so variations.  Once I have finished editing his photos and he has been sold at auction, I'll add a photo to my gallery album with him standing on his base.
Tada!  So now you know how I make my equine fine art sculpture in ceramics.  This one earthenware but I also work in porcelain and fine bone china.
 

I wouldn't get your hopes up on that. We don't get iron staining from our water, and the iron impurities in my kaolins are guaranteed to be significantly higher than whatever might be in my water. Public testing results are under 0.03mg/l, so only trace amounts. We also know for a certainty that iron gives a yellow discolouration in oxidation whiteware bodies. There's a solid chance it is caused by something in my water, but I don't think iron makes sense as we'd see this in all bone china worldwide.

Creeped your insta, my god your slip looks delicious, only way to describe it haha! That pink slip just looks amazing, luminous.

When we produce a ceramic material that allows "light" to pass through that material we are working with a "glass" even though us potters call the material a clay body or a glaze.  
Todays "Ceramic-Tech-Today"  article: Colored glass: From alchemy to empirical chemical design  
https://ceramics.org/ceramic-tech-today/education/colored-glass-from-alchemy-to-empirical-chemical-design/   
has some useful information and background that might help determining why the bone-china pots show a color when seen in a light source.  Remember that the source of the "light" is also an important variable.  
LT
 

After looking at the manual posted in the other thread this controller seems a bit weird. T1 is the time taken to get to the NEXT temperature not the C1 temperature. That seems backwards to any controller I have programmed. 
C1 0020c, T1 0030m
C2 0100c, T2 0030m
C3 0100c, T3 0600m
C4 1140c T4 0100m
C5 1240c T5 0000m
C6 0020c
 
That should go from room temp to 100c in 30min and hold at 100c for 30min. Then it takes 10 hours to get to 1140c (you could speed that part up) and then up to 1240c in 100m (60c/h)

I have a sieve that fits a 5 gal bucket,  I bought it about 40 years ago.  A few years ago the screen started break along the edges,  so I went to the supply store and the same screen had a flimsy plastic body on it.   My  old screen has a heavy plastic body,  my husband sealed the screen in with a waterproof adhesive.   It isn't very pretty but it works  and I have a really small sieve for test glazes.    Denice

Hi Brian_Ire, welcome to the Forum!
We did a pit firing in Wheel I and Wheel II classes, no ferric chloride was used - just pit fire with some smelly biscuits added to the fire*.
The wares came out interesting black, orange, yellow, and baked brown colors...
This article has a long paragraph on ferric chloride safety, and another paragraph on Raku safety:
Natured Inspired Firing (ceramicartsnetwork.org)
Check back, perhaps others with ferric chloride experience will respond...
 
*horses having passed since the last high tide!

I use a talisman at work, and while it’s great for 10 gallon batches of glaze, it would be wildly impractical in my home studio. The cleanup of the brushes is a pain. 
I have a smaller sieve that sits in a 5 gallon pail at home, and I use a large round sash brush to push the glaze through. It works pretty fast and cleans up very easily. 

To give back to the thread, I just had great success adding 4% Veegum T ($$$) and 0.5% CMC gum to my LF clear and then gelled it further with a touch of epsom salts. The result is a bucket with about the worst rheology possible, unworkable by all rights. However, I dipped a couple pots through the glaze, shook them a bit, and got really good even application. It dried well without any cracking. I tested layering and that worked great too! I won't get a chance to fire for a bit, but thickness is good so I can't imagine how it could go wrong from here.

Up to you if ease of application is worth the VeeGum T tax.