High Bridge Pottery

Does that work similar to having a diode across the coil contacts to stop it dumping electricity the wrong way when the magnetic field collapses or is it a different idea? As far as I can tell there's 6 elements in the kiln with one relay doing top and bottom and the other doing the two middle and two center.

The camera does seem to be picking up a slight glow from the middle and center elements, especially in the third groove up from the bottom.

Did they say what was tricky about it? I have bisqued fired in a gas kiln before, the only tricky part was not going too fast at the start as the kiln had no pilot flame so it would like to climb fast on the lowest setting on the main burners. Before electric kilns were common place everybody used to bisque with whatever fuel they used.

Is the thermocouple in the right terminals? Looking at the end of this manual - https://www2.ceramics.nidec-shimpo.com/wp-content/uploads/2019/06/Orton-Autofire-Manual.pdf it seems to say you should have them on different terminals. Can't see the JPR2 to see if it is bridged. Also on their wiring diagram the 6 pin next to it never seems to have 6 wires connected but I have less idea what that all means. Hopefully I am reading the right manual.

They look about the same to me even though some are not very even. Lets hope they are all the same resistance and the floor just have a bigger hairpin. Do you have a multimeter to test the resistance of each element? You would need to turn the dial to select a low resistance setting. Depending on the type it could be 200 Ω or lower like 20 Ω but the lower the better as they will only be measuring around 1-2 ohms. I have drawn a basic picture to give you an idea You will have a black and red probe and put one on each leg/tail of the elemet to get the value. Make sure you turn off the kiln isolator switch first. Still not sure what that black box is doing, I thought maybe it is the relay but then the controller has the relay inside so I guess it is another kind of safety switch? I don't think the bare copper is a problem but as Neil says you can just connect the element tails together with a connector if they are long enough. Edit: maybe an actual picture could help

Will you get the right resistance readings without taking off the connecting wires? I was worried that you could read the wrong resistance but I have normally been working on parallel elements. The only way I could think of is to test the voltage drop across each element but that would mean testing while the kiln is on. After a bit more searching and testing on my own kiln it does seem like you only need to disconnect wires in parallel circuits as there's only one path in a series circuit. Means it should be fine to test the resistance of each element without taking off the wires Even if the floor elements are a different resistance they probably wont be too far off from each other. The total resistance should be 240volt / 15 amps = 16 ohms If all the elements were the same resistance then 16 ohms / 10 = 1.6 ohms for each element. At a guess maybe the floor elements are 1 ohms each and the side wall would all be 1.75 ohms each

Thank you for the photos. Looks like an interesting kiln, is that just bare copper going in between the elements? Not seen anything like that before. What is that black box they are connecting to? I don't think the cracks are letting out much heat to slow down your firings and would imagine the peep hole on the front lets out more. At least the wiring is simple as they are all in series. The only tricky part is working out if the floor elements are a lower resistance to the side wall. I will have a think if there is an easy way to test it but from the element photos you posted the floor element coils do seem to have bigger spaces in between each rotation of the wire than the side wall. Do they look like that in person as it's a little hard to tell from photos? Looking at it a bit more I am confused on how the neutral is getting back, the main wire just seems to have two live wires coming out. Is the power coming in through the thinner cable and the controller is the thicker cable? That makes a bit more sense.

I think it seems to be a glass former, intermediate oxide and flux all depending on chemistry. I would maybe argue that in pottery we are using it more like a flux than a glass former due to its reactions with silica but it seems to be pretty versatile in its use. One comment that got me from the NCECA talk "Glazes without borders" from Peter Berg was that low fire glazes higher in boron were more durable and resistant to attack than high fire glazes with little or none so it seems to be fluxing while also acting like alumina by increasing durability and resistance. There's an interesting comment on the B2O3 page on digital fire that it can even be refractory. "B2O3 can actually be a refractory, frits with very high contents are used in the refractory industry. These frits do not contain SiO2 (depriving boron of a reaction with it to form a borosilicate glass)."

Thank you for the ideas on some test Peter, I will source some HCl soon and report back the results. Will have to look into the sugar and see what that is meant to be doing.

As far as I can tell it is an extended Si:Al ratio showing the relationship of acid (silica) to base (RO and Al2O3). There is a lot of discussion on if you should have B2O3 as an acid or a base and some interesting experiments showing that you can trade Al2O3 for B2O3 as they are both sesquioxides (an oxide in which oxygen is present in the ratio of three atoms to two of another element) Some argue that if B2O3 was an acid you should be able to reduce silica when adding boron but most times you need to increase silica when adding boron so how can it be seen as the same as SiO2. If anybody wants to get copies of the Transactions of the American Ceramic Society volumes you can find them here - https://archive.org/search?query=subject:"American Ceramic Society" All in the public domain so I assume I am fine sharing here as it's not for commercial use.

I am surprised pottery crafts said they wouldn't do it, probably just being lazy as they don't have the specification on file. The few places I know who would probably wind them for you are https://www.kilncare.co.uk/elements https://www.kilns.co.uk/kilns/kiln-elements https://www.cromartiehobbycraft.co.uk/Catalogue/Ceramic-Kilns-Electric-Kilns-Pottery-Kilns/Kiln-Spares-Kiln-Elements/Kiln-Elements-Element-Wire-Connectors

A bit more searching and I have found how they are calculating the oxygen ratio. Orton seems to say it is only useful in comparing similar glazes and they all seem unsure if you need to include B203. I have no idea what to do with it yet.

Yes you are right They don't look in too bad shape but if it is taking ages to fire then worth getting some new ones made up. The trickiest part is working out what resistance each element needs to be as that depend how they are wired up and what KW output you need. If you can get a photo of how they wire at the back then we can go from there. You can try measuring the resistance but it will change as they degrade and you would need to remove the feeder wires first otherwise you could get the wrong reading so probably better to work it out from the wiring. I wouldn't take them out and try posing as they will probably snap in transit. It will be easier just to work it out with them in place. Looking at them all the side wall seem to be the same resistance but the floor coils look like they have bigger gaps in between each coil so will be a lower resistance (if they use the same gauge wire) You really need to know the resistance of each element, the internal coil diameter, the wire gauge, the length of each coil, the length of the hair pin and the length of the tails, voltage and kw

I would think the normally open yellow wire is the one going into the coil on the left and the brown is coming from the far left pole on the main bit. Not sure which blue is going there from the right side of the coil or where the red is coming from. I guess the black wires are going to a tungsten indicator bulb somewhere. It's a strange box as there doesn't seem to be a wire coming from the controller to that box to make it do anything. Maybe that plugs in another way. Thinking about it again the brown coming from the main contactor makes no sense as then the power would only flow when the coil is on.

Thank you

After a bit more digging I have found the actual paper they are talking about in stull's discussion. It just isn't listed anywhere besides a page number with no volume so it was in volume 7 after all.

The only reason I brought it up was because I feel if the door interlock was faulty then the controller would also be having issues and as that is not happening I feel you can rule that out even with it being old.

If the safety switch was going bad the controller should be turning on and off I think. When you disconnect the interlock does it power down the controller? That black box looks a familiar shape to something I have seen before to control kilns, I can't remember how it worked though. I am guessing that's where the soft click is coming from which means it should be sending 240v to the contactor coil to close it and that isn't happening. Hard to know without being their when it fails.

The lowest it gets is 10c/50f so it can be pretty cold as I don't heat the room as much as the rest of my house. The molds will be around that temp too. I will have a go at mixing up a few tests removing different ingredients and see if that produces any results.

The door interlock is just a safety switch and not a relay. Just there so you can't send power to the kiln while the door is open. When it fails can you hear if the small click is coming from the controller or from the main relay/contactor. Whats confusing me is you say it can also fail when trying to start a firing and not hot.

Think I got the wiring slightly wrong so here's my updated version. Neutrals were in the wrong place and not all connected to L1 which was confusing me. Sedgefield Pottery is pretty close to Durham I think.

Doesn't look like the nicest connection but at least it is connected Has it got 12 elements? 6 a side? I tried to figure out how it's wired and this is what I came up with (could be wrong)

I have managed to find Transactions of the American Ceramic Society vol 2 through 19 so got a lot of reading to do. I haven't been able to locate Professor Binns article in volume 7 which seems to be looking into matte glazes too which is talked about in the comment/discussions. I want to try and figure out why they are interested in the oxygen ratios. Edit: I managed to find C. F. Binns article in volume 5 after looking in the collective index Strange that the files don't total 1000kb but it seems to stop me putting them all in one post. Will continue in another post.

Is this red wire actually connected to anything? Hard to tell from the photo but it doesn't seem to be going to any of the barrel terminals. The white colour on the top red wire (L1) seems to hint it is getting very hot.