Piedmont Pottery

Delayed cracks can be indicative of a glaze with a thermal COE lower than the clay body.  You might try to increase your glaze COE a bit to see if the cracks still happen.

I have worked with a decal company with original logos and script etc.  They usually send a copy to be proofed.  They are also knowledgeable about their product.  Another suggestion for @Joe from Chagrin Falls is to have a potter create the plates and have a painter/watercolorist paint directly on the bisqued plates with underglaze.  Then the potter can clear glaze then fire.  I have a friend who has worked with me before.   Just a thought.

If I was starting over now I'd invest in nitride-bonded silicon carbide shelves, not necessarily Advancer brand, there are lower cost options from other suppliers.  The lighter weight, durability, and ease of cleaning glaze drips are worth the investment in my opinion.  

It looks to me like you had enough organic materials in the kiln wash to create a reducing environment in the kiln and you got a lot of carbon going into the surface of everything.  If that is correct, refiring with plenty of air available, e.g., peeps open or lid propped open just a bit, should burn off the trapped carbon.  Fire it up to your normal working temperature.

I'm with Bill. Making people calculate volume is a big pain for everyone involved. Asking most people to do that sort of math is not a good idea. Weight is a much easier way to do it, and you can easily have different pricing categories for big wide pieces like serving bowls that take up a lot of volume without much mass, and cups and such that are more compact. Or better yet, just include glazing and firing costs in the price of the clay. It keeps students from feeling like they're getting nickel-and-dimed to death, takes away a cumbersome step in the process, and makes it easier for people to  track and budget their pottery class spending.  I've done it by weight from day one, and it works fine. It's easy enough to figure out the approximate weight of clay in a typical load and calculate all the associated costs of firing and come up with a price. Plus it motivates people to throw thinner with less trimming, and makes them think more about the technical aspects of clay work like avoiding cracks and warping and whatnot that may keep the piece from getting fired.

Mosquito larvae enhanced the plasticity.
(Just kidding. Don’t try it.)

Instead of using a lubricant we put the clay to be extruded into a thin plastic bag open at the die end.  Clean up is just the die and the last few centimeters of the extruder tube.

Wollastonite is not hygroscopic.

As long as none of your ingredients are wet there should be zero problems with this.  Ive done this for years with -20f temps.

Have you explored the Digitalfire web site for information on your problem, or even downloaded their glaze calculator?  Altering a glaze is a tough situation and takes lots of understanding. If you are just getting into glaze mixing I would try finding a glaze that meets your needs without making changes. Try Glazy or Digitalfire.
 
 
best,
Pres

You can also try a "candling" program.  I run the kiln at 180 degrees for 8 hours.  Do not go above 212 degrees (boiling temperature), and be aware of any offsets your kiln may have.  Make sure your work is not too thick.  Sometimes I touch the piece to my face and if it feels cool I let it sit for a while longer.  It's humid now in Indiana, I can't imagine what you go through in Florida!

Epson salts are basically magnesium sulfate. 20% +/- magnesium; which is the clay world is a body flux. The sulfates will burn out. Given the amounts used; nearly zero effect. At most, the magnesium will change a high white body to an off white body; and that would require larger additions than what is being discussed. 
Tom

In addition to using smaller buckets, adding a bit of Epsom salts to flocculate the clay will make the fine particles settle much more quickly, allowing you to remove the clear water above the clay layer.

I think that Tony Hansen's demonstration of the fallibility of ChatGPT is worth posting.
ChatGPT is completely wrong about the cause of glaze crazing!
https://digitalfire.com/picture/3159
... a fine example of ignoring the elephant in the room.
... a fine example of ignoring the elephant in the room by ChatGPT
PS It reminded me of a very old software engineering joke (1970s?).
A man was been taken on a cross-country flight in a helicopter. During the flight the ground became completely covered in dense fog, and the pilot became lost. The eventually came across the top of a office tower sticking above the fog, and they hovered nearby. The man attracted the attention of somebody in the office and held up a placard saying "where are we?", and received the answer "in a helicopter hovering 60ft above the ground".

The pilot said "OK I know exactly where we are, and set off towards their destination.
Later he explained "the answer you got was technically correct and not the slightest help, so obviously we were at the Microsoft help centre whose location I know".
Maybe ChatGPT is another help centre.

In addition to using smaller buckets, adding a bit of Epsom salts to flocculate the clay will make the fine particles settle much more quickly, allowing you to remove the clear water above the clay layer.

It appears that the pits go all the way through to the body, so the bubbles are starting there. You say the body is rated for cone 5-10. That means it is immature at cone 5/6, not mature until 10. An alleged  wide firing range is one of the unfortunate fallacies perpetrated by the clay industry. My guess is that there is still stuff outgassing from the body at cone 6. If you are using a kiln with a digital controller, you can try a controlled cooling to allow the glaze to heal over any bubbles that are coming up.
As for the unexpected color, I'm not familiar with that glaze.

If the timer shut it off before the cone dropped, then it didn't reach temp. Turn the kiln on high for a few minutes and see if all the elements glow. If one is out, then it's probably just a fried element. If two in the same section are out, then you probably have a bad switch. Or in both cases it could be a wiring connection fried out somewhere, which should be easy to see when you open up the control box (with the kiln unplugged). If they all glow, then they're probably worn and need to be replaced. Post a pic of the elements so we can see their condition.

Definitely check out everything Bill recommends. If everything looks good, then I would replace the wires going into and coming out of the switches. If they're old they can cause overheating.

As far as a clay being vitrified at cone 6, it depends on the clay you were using. A clay body that is sold as a cone 6-10 clay will be a lot more porous when fired at cone 6 than it is at cone 10. For food dishes, I find it’s best to aim for your porosity to be less than 1%. Even if your clay body is a true midfire clay, it’s always a good idea to do a porosity test to confirm against manufacturer’s specs. Your method of firing may be different than what the manufacturer used to supply that info.
The colour seems unusually vivid for mould growth, and usually there’s other colours involved as well. What it cleans off with will possibly also give you more info. 
If it cleans off with hot soapy water, bleach or peroxide, that would indicate bacteria of some kind. Or maybe something it picked up from the counter? I have kids, so my mind goes to something like drink mix, or dye transfer from some kind of wet packaging. 
If you need something like vinegar or CLR to remove it, that would mean it’s probably from the water.

Hi @John Flores, welcome to the forum!
This happens when the wires get old, and those wires are old. They are white when they're new. Old wires can burn out a brand new relay very quickly.
1. Get a new terminal strip.
2. Assuming the feeder wires are connected to the elements with the standard Skutt crimp connectors: Cut off all the slip-on terminal connectors on the ends of the feeder wires that connect to the terminal strip, and put new connectors on them. No sense using corroded connectors on a new terminal strip. Replace the feeder wires next time you replace the elements. If the feeder wires are connected to the elements with removable connectors, then replace the feeder wires now. In the future, replace the slip-on terminals any time they show signs of overheating.
3. Replace the relay.
4. Get a new wiring harness (for inside the control box). It has all the wires going into and out of the relays and all the red control wires. I don't usually replace the control wires unless they really need it, but yours are looking fairly corroded so I'd replace them. Be really careful removing the wires from the transformer. Those connections are really delicate.

I'd be mad. They should have installed the outlet to match your kiln, not modify your kiln without asking you. It's pure laziness, and because they modified it, they may have voided the warranty and/or UL listing. Make them replace the outlet with a 6-50 and make them buy and install a new power cord.

I would get the larger kiln. 8 sided kilns are fairly limiting in what you can fit in them.
You can get a wall mounted digital controller from Skutt or others, which basically turns your kiln into a digital kiln. You'll still have to turn on the Sitter, but the firing will be controlled by the digital system. They're not cheap, but you'll still be saving about $1500 vs the cost of a brand new kiln.
With a used kiln, make sure the bricks are in good condition- only small chips, no large breaks. Also check the lid and floor for cracks that go all the way through. Hairline cracks are normal. Also, if the bricks are very yellow in color then that's a sign that they've been fired a lot and are near the end of their life. White/cream colored bricks are what you want.

I don't do a lot of throwing but I have learned that keeping the  thickness of the clay the same is the key.   I even try to keep the turns in sculptures  the same,   If I can't I will make the area angled to ease into a area with varied thickness.  My throwing teacher in college would walk behind our wheels hollering (compression, compression, compression)  especially on a flat platter.   Denice

Have you tried using a rib and compressing the heck out of the bottom while on the wheel?

Crazing has very little to do with your cool down rate. If you slow your cool and it appears to get rid of a crazing problem, you’ve likely only caused a crazing delay. A shock test will still bring it out. Crazing is caused by COE values that differ too greatly between clay and glaze. If this is your first test of using Frost instead of the Standard 365 clay and all your usual glazes have crazed, that just means the 2 clays have different COE’s. That’s not unusual at all. 
If you want to keep using the same glazes, you’ll have to adjust them all to compensate. If the crazing is slow to emerge and the crack pattern is a larger one rather than a covering of fine lines, chances are the glazes won’t need a lot of adjusting. That which bodes well for keeping the character of the glazes intact. It’ll be a little bit of work with a test sieve to hone in 10 glazes, but it’s doable. 
If you’re going to use glaze software to help narrow the project down, some notes about comparing COE values:
1) Using calculated COE values won’t eliminate physical testing, but it’ll cut down the work and materials used. 
2) COE values aren’t absolute numbers. They’re only a snapshot of a measurement taken under a very specific set of circumstances. If you change the circumstances, you get a different value. They’re good if you’re adjusting a glaze without adding or removing any ingredients, only changing quantities. Also worth noting that because of this, different glaze softwares use slightly different COE values in their source tables. If you’re looking at a clay manufacturer’s suggested COE range for glazes, make sure you’re using the same software they are. Many manufacturers have stopped offering these suggestions though, because they tend to cause more confusion than they help with.
3) You don’t want to match coe values of your glazes to your clay. That results in more glaze flaws. Knowing that you need to move your existing glaze COE values higher or lower is the important bit here.