So every other element was orange, like just one in each ring?
Does your kiln have zone control, or just one thermocouple?
Did the controller say CPLT (complete) at the end of the firing?
Unless you put in a cooling cycle, the elements should not still be on. If the glazes ran, then either the glazes are too fluid or the kiln over-fired. Slow cooling does not cause all that much additional melt.
My first guess is that you wired it wrong. I looked at the wiring diagram, and it's fairly goofy as far as kiln wiring goes, so it wouldn't be hard to to it wrong. It looks like maybe they're using the safety output on the controller to run a main relay? Go through the wiring diagram and see if you got it right. The other possibility is that you have a dead relay. From the wiring diagram it looks like if one was dead then that would account for an every-other-one glowing situation, although that wouldn't account fir it glowing after the firing is done.
People are always asking about element life, so here are my thoughts on that subject:
On my personal kilns I get 150-160 firings out of my elements, doing a combination of cone 04 bisque and cone 6 glaze, probably 35% bisque and 65% glaze. This is true for both my big 21 cubic foot kiln and my small 4 cubic foot kiln, and is consistent from year to year. Both are L&L kilns with standard elements, not quads. I see similar numbers in my customers' kilns of all brands. I have to change the elements in my small kiln every year, in my big kiln every 2 years.
According to my records I've currently got 241 firings on the thermocouples on my small kiln. I should probably check those soon. They do tend to last longer than the elements, though, because they are thicker and are in protection tubes.
Only firing to low fire temps makes a big difference in element life. Today I did a checkup on an L&L E23T that I installed in a school in 2009. They do about 55 firings a year, all low fire- bisque to 04, glaze to 05. The kiln currently has 418 firings on its original elements, relays and thermocouples. The element resistance is almost perfect. Visually they're starting to show their age, though, and I expect that they'll start to degrade more quickly over the next year. I told them to budget for an element change at the end of the 2017-2018 school year. I wouldn't be surprise if they hit 500 firings.
All of this is subject to what's going on in your specific kiln, though. I have a customer who only gets 70 cone 6 glaze firings out of her elements because she does a really long, slow soak at the high end. She could get 100 with a typical firing schedule. The types of glazes you use, and how you load the kiln will also effect element life. Don't put your pots right up against the kiln walls! I'm also convinced that doing a combination of bisque and cone 6 will get you more cone 6 firings than just firing cone 6 all the time. I have absolutely no science to back that up, but my customers who only use their kiln for cone 6 glaze firings tend to get a slightly fewer firings out of their elements.
Maxing out your kiln will cost you. I have a customer who is using their Skutt 1227, 208 volt single phase kiln for cone 5. On that voltage and phase it is only rated for cone 5, so they are maxing out what the kiln can do, and it's definitely costing them. Once the element resistance changes just a little bit, the kiln can no longer get to cone 5 and we have to change the elements. If the kiln was rated for cone 8 or cone 10, it could handle more resistance change before it struggled to get to cone 5. The customer is supposed to be trying some firings to cone 3 with a hold to get to 5. Hopefully that will work out and help with their element life. In my tests, higher temps seem to burn out elements faster than holds.
Keep your elements clean. Vacuum out the kiln occasionally. Monthly would be fine, but definitely any time something blows up. All the little shards on the elements cause hot spots, which lessen the element life. I worked on a kiln at a school once that was only used for low fire pots. The teacher never vacuumed it out when the kids' work blew up, and the bottom element was full of shards, like really full. As we all know, low fire clay melts when it gets too hot. Well, the clay shards caused enough hot spots that all of the shards melted and fused the entire bottom ring of the element into the bricks. It was just a big tube of glass filling the element grooves. I had to replace all of the bricks in the bottom row. $$$
Rather than getting a replacement controller from Paragon, call Bartlett Instruments and buy it directly from them. It'll be a lot cheaper ($219), and you'll have all the benefits of a controller that's made for firing pottery and is easy to install with all the same wiring.
Pretty sure it's the bentonite. It's just shrinking way too much. I've never seen a recipe with that much. Drop it to 2% and put the rest into the kaolin. You'll probably need some epson salts to keep it suspended well.
Each material has a different weight per unit of volume. A cup of frit is about 300 grams. A cup of silica is slightly more. A cup of EPK is only about 125-150 grams. Plus if you go by volume, the amount of material actually present in a scoop will be different each time due how tightly packed the material is in the scoop. Do everything in grams for the best accuracy.
I've seen a number of kilns damaged when low fire work was fired to cone 5/6. It can not only melt the pots all over the shelves, if you've got a full kiln it will ooze into the bricks and elements. I've seen a few kilns that had to be thrown out because it was so bad.
In my studio the rule is that I only fire clay brought from me, and that I only fire for my students. I don't want to be in the business of firing. If someone wants to be an independent artist and make work at home then they need to have their own kiln. If not, then they need to be part of a studio.
Firing work for 'outsiders' puts way too much liability on you. Even if the piece doesn't melt, folks will complain if their glaze doesn't come out the way they think it should, or if the piece cracks, etc. You'll get the blame and your business may suffer from it. It's just not worth the effort. The only time I will fire for someone that's not a student of mine is after I interview them and figure out their experience level. If they've got a degree in ceramics, then I'll consider it. Anything less and I say no.
I think handmade plates and platters should be as thin, or at least close to, as commercial plates and platters. Unless they serve some special function where they pretty much just sit in one spot for a long time, they need to be thin so that they aren't annoying to use. I want to be able to lift 4 to 6 plates out of the cabinet at a time when setting the table. I want them to fit between the dishwasher tines easily. Just because they are hand made doesn't mean they shouldn't function every bit as well. There's not necessarily a specific thickness I shoot for, but if I pick it up and it feels too heavy, it needs more trimming.
Firing to cone 6 will max out that kiln, which means it will fire pretty slowly at the end, which also means you're wasting a lot of electricity. Typically you want a kiln that will fire 3-4 cones higher than what you'll be firing to, so it will have plenty of power to meet your firing schedule. By maxing it out, you're at the mercy of the kiln when it comes to setting the schedule at the high end of the firing. And when the elements start to age even a little bit the kiln won't be able to reach its max. If it was rated to cone 10 and you were firing to cone 6, you could get away with firing on older elements because you're not at its peak.
Many 120 volt kilns are underpowered, and yours is only a cone 6 kiln so it's even more underpowered than a cone 10 version. At a cone 6 rating it really shouldn't be fired higher than cone 3. They need everything working properly in order for them to function correctly. At 8.8 ohms your elements are 10% off from the factory original, which is exactly the amount of wear when replacement is recommended. Assuming everything else it working properly (thermocouple, relays, etc) then it's probably the elements causing the problem.
Test it out and see what you think. It may or may not be a problem. If needed, reformulate for whatever you have access to, be it Gerstley or Frit. Frits do not settle badly if you have a well formulated glaze with enough clay to keep it suspended. The problem is that a lot of old glaze recipes relied on Gerstley to keep the glaze suspended, which it does very well. So if you substitute a frit in those cases then you can have suspension problems.