neilestrick

I think it depends on the glaze, and whether or not it is melting enough at cone 5. Why not just do it with a cone 5 glaze? It works with the silicon carbide, too. 7% is likely overkill. I've had glaze lava with less than 1/2 of 1%.

The thermocouple could definitely be the cause. It could be a bad connection somewhere along the TC system, or a split in the weld that's opening up as the kiln gets hotter, or just a bad thermocouple (it happens). @ShanRums Have you done a factory reset on the controller? Is there a thermocouple offset in the controller? Is there a protection tube on the thermocouple?

How far into the kiln does the thermocouple go? Is it in a protection tube? post some pics of the thermocouple so we can see what sort of condition it is in.

I don't think the kiln slowing down is going to cause over firing of 3-4 cones. If the elements are worn enough that they're slowing down at the end, it's not going to be able to slow down enough to get that kind of heatwork without the controller putting up an error code. I think this is a calibration issue or a thermocouple issue. I replace elements in dozens of kilns every year and over firing has never been a result with worn elements. Or if it was it was so little that it wasn't an issue. One time I even intentionally fired one of my kilns until the elements were so worn that they couldn't reach cone 6, and it never over fired. The cost of firing doubled, but it had no issues with accuracy.

With cones on the shelf so that you can see them from the peephole, run it at 150C/hr up to 1050C, then 60C/hr to 1250C, and watch the cones, When cone 6 drops, note the temp and shut it off. Then do another firing with the same program with the last 100C at 60C/hr to whatever that temp was and see if it works. It's really far off for thermocouple calibration, sot best to just figure out what temp you need.

Grolleg porcelain (no ball clay) dries quickly, because it is not very tight in raw form. Porcelain bodies are only about 50% clay, so they don't hold as much water as stoneware bodies, and give up the water quickly. Fine grained white stoneware and other bodies that are high in ball clay dry quite slowly because ball clay is very fine grained and makes for a very dense body.

Don't go adding any holes until you try the bag wall arrangement first. One change at a time. Plus the holes are unique to Alpine kilns, so they may or may not actually help you. I've never found them to be necessary in any of the kilns I've built. Plus updraft and downdraft behave differently.

Yes, just like that. If you can cut everything a little narrower to give some more space that would be good but this is a good start. Like Bill said a 1/2 width brick for the target would be preferable. You can cut hard brick with a masonry disc on a circular saw pretty easily.

You've got a lot going on there. I would try a short bag wall, just a row of bricks on end with small gaps between them right along the shelf, and one target brick in the firebox about 2/3 of the way to the back wall.

I epoxied a wood disc to the back of a 16" porcelain platter last year, lots of surface area joining, and it fell off in just a few days. I prefer a mechanical system- wire through a hole in the foot or something like that.

Not a lid gap issue. Like Bill said, something else is going on. Is this the first time it has done this, or has this phenomenon been repeated? It's possible an element connection fried or something like that. I would turn it off and open up the control box and make sure there aren't any wiring issues, and if not then start looking at the digital system. Maybe a high limit or a hold in the program accidentally?

I've got two kilns in my shop right now that I'm converting to digital systems. One is 35+ years old and never been fired, the other is 33 years old and has only been fired a handful of times and only to low fire temps. I only paid $1000 for the pair. Old kilns can be a great value!

You'll want to use a clay body that fully vitrifies, and I would go with 3/8" thick if they're over 4" wide. If you're new to making tiles and aren't set up for making and firing them, doing an entire bathroom floor will be a major undertaking. Tile production is a different beast than making pots, and doing it efficiently requires different equipment and a different way of using studio and kiln space. You may want to consider using commercially available tiles for the bulk of the floor, and just make some accent tiles to personalize it. Also, the process in that article may or may not work for you. Leaving tiles open on a slab of drywall may or may not allow them to dry without warping. It all depends on your clay body and the humidity level in your studio. With a heavily grogged clay they will be more likely to remain flat, but that type of clay may not be appropriate for the type of tiles you're making. If you're doing any carving then you'll want a smooth body, and they will be more likely to warp. The thickness of your tiles will also affect how easily they warp. Try making a batch and see how it goes. You'll have to figure out what works for your situation.

Bill's solution is the simplest and best way to go, because that box isn't set up for relays. There's no heat shield, and it may or may not be deep enough or have enough ventilation for them.

I customer once gave me a wall-mount Orton digital controller system. I hooked it up to my old manual test kiln and I've been using it for almost 10 years now.

Often I'll just work in silence. I don't get that very often in the studio so it's kinda nice. But if I need some sound I'll turn on a Pandora station or a mix on my laptop.

If you know it's firing hot, then it would be worth your time to run an empty load with cones and get it dialed in so you don't have to watch it. It may take a couple of firings, but it'll be worth it in the long run to be able to trust your controller.

The control can make changes to the final temp depending on the speed of the firing, to make sure the proper heatwork is achieved. It also depends on how the controller is set up- whether it shuts off the kiln when the average of the sections reaches the set point, or if it turns of when any one section reaches the set point. And sometimes it just overshoots a little bit because the elements take a little time to stop radiating.

If you're getting little shavings then something is rubbing. If the blades aren't rubbing along the chamber, then they're likely coming from the end(s) of the shaft, like maybe a bearing is giving out and/or the shaft is shifting and rubbing somewhere. Dig around, you should be able to find a spot where metal is wearing.

Bluebird makes good mixers. That's a nice little machine, great for small batches.

Cement generally doesn't hold for very long with that type of repair. If it fails, use element pins to hold the broken brick pieces in place, or if they're too small, remove them and just pin the element in place. Replace the broken bricks next time you replace the elements.

I think this is the answer. Every time I've actually heard pieces blow up, the kiln was around 500F. It takes a lot longer for the heat to penetrate and cause problems than we realize. So why does Bartlett program their preheat to hold at 180F? Probably because it makes their lives a lot easier. If it was set at 240F, or anything too close to 212F, they would have to educate their users on the subject, and they'd get blamed every time something blew up. They'd be dealing with phone calls and email on the subject every day. 180F works just fine, and it's far enough from the boiling point that if something blows up it's definitely not their fault.

Also try US Pigment. They still show talc on their website.

The wiring diagram on the Bartlett website is the standard wiring setup used on pretty much every modern digital studio-size kiln used in the USA. The only real difference you'll find in most models the number of thermocouples and number of relays/outputs used.

Thank you!