Babs

After firing and in situ. :-))

Ok, now download the firing log and feed that sweet thang into @jay_klay_studio's graphing program to visually see the tracks of the 3 sections. And if you really want to have some fun, add another 9999 drop all the way down to 100 after your regularly programmed cool to log how looooonnnggggg it takes for the last several hundred degrees. Several times over the years I've printed the extended graph of a few kilns as a teachable moment for the students of the virtue of patience, i.e., "Can I get my piece tomorrow?" "No, next Friday."

That's a cone 05, not 5. That would explain why the cone 5 glazes didn't melt.

I usually fire my kilns at night so I don't really see what's happening with actual temps in the kiln, but today I started it up in the morning and was in the studio in the evening and got to see exactly what was happening during the cooling cycle. I do a slightly-slow cooling cycle to even out the results in my 3 kilns because they all cool at drastically different rates due to their sizes. I do a drop from the peak down to 2000F, then cool at 175F/hr down to 1500F. This gives me identical results from all 3 of my kilns. This firing I'm talking about here is in my 10 cubic foot L&L EQ2827-3, which has 3 zones, and was packed very tight in the middle. I was surprised at just how much slower the middle cools compared to the top and bottom. This photo shows how it's going part way through the initial drop from peak temp to 2000F:

As you can see, the middle and the top are nowhere close to each other. In a normal firing segment, a 73 degree difference would stop the firing with an error code. So why isn't it doing that here? It's because the cooling rate is set at 9999, or full speed. Any time you use 9999, whether it's climbing or dropping, the controller lets the kiln do its thing and doesn't care if the sections aren't even. Firing up or down at 9999 is the fastest, but you sacrifice evenness. As the temp continues to drop, we see this:

Here you can see that the top section (TC1) has started firing again. The set point for this segment was 2000F, at which point it should start cooling at 175F/hr, yet the top section passed that by about 20 degrees before the relay kicked on and the controller stopped the drop. Why did it let it get so far below the set point? Because it's averaging the 3 zones. Once the average of the 3 zones hits the set point it will start to fire each section again as needed to match the set point.
I get a lot of questions from customers about error codes and cooling cycles. The biggest problem is that the kiln can't always keep up with the programmed cooling rate. There are a number of firing schedules out there on the internet that people are trying that use a rate of 600F/hr or more for the fast drop portion of the cooling cycle, and many kilns simply cannot cool that fast, especially the middle section. When you have a specific rate programmed, the controller will send out an error code if the kiln can't keep up with that rate. So if you want a really fast drop you should use 9999F/hr, not a specific rate. For most people doing slow cooling with cone 6 work it won't matter if the sections are not totally even during the drop. If you do need more precision, like if you're firing crystalline work and it's important that you don't overshoot any target temps, then you'll want to put in a slower drop rate that the kiln can actually keep up with, and the controller will keep the sections even and not overshoot set points.

There aas a thought that smearing your statue with yoghurt would hasten the mould etc growth on it...

There aas a thought that smearing your statue with yoghurt would hasten the mould etc growth on it...

If the clear glaze formula is the base for the white glaze, you probably could,  with the colorant exceptions noted by @Hulk, but why would you want to? If your oxide decorations are sometimes changing  your  glaze surface, try mixing a little of the  glaze into the oxide.

Minor update to anyone else in my boat. I pinged him on Facebook again and actually got the most detailed message out of him I have. “Good news Morgan, I have your order printed out and I see your PayPal payment”…then radio silence again ha! Maybe I actually get these sometime in the coming years…who knows.

The easy fix is use a liner glaze on inside and ash glaze on outside-issue is done.
If that sound to hard (an inner and outer glaze job) try- below
Since you are using a iron clay a hotter bisque any help by making sure all organics are burnt out 
yes it looks like the glaze is peeled back clean to me as well. burnouts or ash peeling it back is my guess. Even in oxidation as Kelly said the inners are a slight more reduction  or lets say not as oxidized. One nice liner glaze inside will fix this in a heartbeat

Can't remember details but on the grounds that most folk heat their pareafin was too high, sone advised adding a bit of lavendar oil to the wax bath . As soon as oil is smelled, lavendar wax is hot enough and thermostat should be set at that temp. 
Still poses prob on burn off in kilnn but not when waxing pots. Church candles here too.

That's getting up there! What firing range is written on the bag?
Do as Kelly suggests but I'd be tempted to do just a couple as could be unsuccessful. Won't turn out like a pot bisqued to C 06 or 04.  Would be nearing the end if its firing range at C 3 and if red clay the coloyr wiuld be pretty dark. 

Can't remember details but on the grounds that most folk heat their pareafin was too high, sone advised adding a bit of lavendar oil to the wax bath . As soon as oil is smelled, lavendar wax is hot enough and thermostat should be set at that temp. 
Still poses prob on burn off in kilnn but not when waxing pots. Church candles here too.

If the first glaze saturates a thin wall then you apply a second coat or glaze the clay can't absorb the extra moisture without pulling away from the clay. I'ld try adding some gum to the ash glaze and then apply the Leach glaze when the ash one is just dry enough to handle. Don't wait too long before applying the Leach glaze.
BTW the David Leach II glaze looks like a cone 10 recipe that someone has added just a titch of boron frit to. Does't look like a cone 6 recipe.

Test the black mentioned above by Min. The cobalt may bleed in certain conditions and some glaze movement, at C 6 a great black.

I think it's probably not asbestos being made that recently. However even if it's not, the silica fibers from whatever they did use aren't really any better, so wear a mask and act like it's asbestos.

The original recipe for Magic Water by Lana Wilson is: 1 gallon water 3 Tablespoons liquid sodium silicate 1 1/2 teaspoon soda ash  -OR-
1 gallon water 9.5 grams sodium silicate 3 grams soda ash You will find many variations of  this on the web if you do a search. I use the one listed above.  
 
best,
Pres

My guess is the handle got bumped and hence the crack . If it was fine for years of use then cracked it got bumped . If it cracked right away(1st month) its a poor connection

if its just been bisqued bisfix will work fine for this. See above video
There are other menders that work as well like Marks mender and highfire mender for glaze wares-I have used them all

Bisque Fix?
 

The things being discussed here is are not necessary to good glaze formulation. I've been making durable glazes for 30 years without ever looking at a Stull chart or Katz's papers. Learning the basic of glaze formulation- fluxes, stabilizers, and glass formers- will serve you just fine, and allow for tweaking formulas to increase durability and adjust glaze fit for your clay body.
Commercial glazes are not necessarily any more durable. They all take testing as well. Clear glazes are generally quite safe if they're free of lead and cadmium, which most all glaze recipes being used nowadays are, and they don't have the heavy metals (colorants) in them that are likely to leach in a poorly formulated glaze. The benefits of mixing your own glazes are that they are much less expensive, and you can alter them as needed to fit the clay body you're using. If you know another potter that has a good clear glaze, by all means ask them for a recipe.

I use the heavy canvas fabric that you can purchase with the slab roller,  I have one for light clay and the other for dark.  I also like the idea of the fabric backed vinyl,  I will have to dig through my husband's scrap box and see what he has.   We have been on a buy only what you really need binge for a couple of years.   We also have been donating truck loads  of stuff to the DAV,  I don't think he would give away upholstery scraps for his cars.  His mother died during COVID and we ended up with most of her treasures  in our basement.   We have enough for one more truck load  and I will be able to walk through my sewing room.    Denice

Hi and welcome to the forum.
Couple things, Mayco Stroke and Coat is a highly pigmented glaze, you don't need to brush a clear glaze on top. Second thing is Mayco recommends a minimum firing of cone 04.
Could you post a picture of the problem tiles? Might help clarify what is going on.

Looking at your pictures I agree with others that the form was thrown too thick, and needed more aggressive thinning to make up for the difference.  I Love throwing large bowls, and other forms for the kitchen, and these require a major amount of wedging of the clay, Mastering the clay on the wheel(coning up and down), and aggressive pressure from the base up into the cylinder walls. Throwing a bowl starts with a rounded interior when opening up, and most of the pressure during pulling is from the outside with more of a flat fingers on the interior keeping the curve of the base into the cylinder then when sufficient pulls have thinned the base the walls are shaped from the inside. My favorite tool for this is a large wooden spoon with the handle cut off and the edges rounded out where the handle had been attached. Whether a dish(flat interior bottom) or bowl (rounded interior bottom) the trimming is important to make certain there are no areas in the base that are thicker than normal fo any thrown piece.
All this IMHO, meant to be helpful, not critical.
best,
Pres

Looks like typical thickness blowouts to me. I've seen them in that location before. I'm surprised that the preheat didn't prevent it, but that could be related to the location in the kiln, stacking, and how quickly the firing ramped after the preheat.

Thank you for the photos. I believe you made the pots too thick. The outside profile vs. the inside shape shows it, to me, clearly. If the bowl is in fact 20” wide, the foot must be well over an inch thick in some areas. 
There are many variables (relative humidity, clay body, temperature of candle, etc.), an eight hour candle ought to have taken care of most of them, but honestly it’s just too thick and blew up. Water did that.