Bill Kielb

Depending on height that might be a tough shape. As a practical matter though I would say first find out how much power you will need in Btuh. So let’s say if we start by taking all the watts it’s rated at now and multiply by 3.41 to convert watts to btu. A 10,000 watt cone 6 kiln in theory needs 34,100 btu to heat equivalently to cone 6. But wait, gas kilns need a flue and likely lose 50% or more of their heat through the flue. So in the example above you could size it at 150% - 200% or more to get burner sizing as the gas is infinitely adjustable so getting less heat just means dropping the gas pressure a bit. Then once total btu is known work backwards for number of propane bottles likely needed. As I said, this might be a tough shape to design in gas, I would refer to similar kilns already converted and see how many burners they used. Once you have a total energy needed it is easy to divide that up amongst smaller burners. If you intend to fire to cone 10 then that will cost you a bunch more energy. I think Olympic makes a round updraft prox 30” tall that uses 2 burners about 250,000 btu to get to cone ten. You likely will be in this range for energy but 4 small burners at 30k-50k each may even things out and a minor change in orifice size makes this easy to start conservatively at 30k and ramp up to 50 k or more. More small burners will provide better control at the beginning of firing when very little energy is needed and more consistency when oxidizing or reducing. so approximating all that above, 1 gallon of propane yields approximately 92,000 btuh. Pick a low and high consumption per hour, let’s say 50k btuh (low) to 150k btuh (high) means 0.5 gallons to 1.6 gallons per hour for let’s say 8-12 hours. A 20# grill type tanks hold 4.6 gallons full. A 40 pound tank is 9.2 gallons and so on. As your firing progresses you will consume more gas and the tanks will cool or ice which often means you will want to err on larger than smaller or have spare tanks ready as iced tanks will have reduced output just when you need it most. Double check my math.

Careful, would rather enlarge around your burner first. Any hole cut ought to be 90 degrees to the burner and on the same centerline or elevation of the burner. Flames will begin to emerge as you go into reduction so if this is not low enough it will hinder how you can reduce. Some pictures below to maybe give you ideas. Ignore the upper hole it is for soda injection. Also. Pic of Example of shelf as your bag wall as well. Just some ideas. The goal would be to get you enough secondary air so your damper could be closed as customary or even a bit more to help retain heat but make sure your flame is oxidizing still. You can always close the damper more to drive it into reduction pressurizing the kiln from top to bottom. Enough pressure and flames start to jet out your lower spyhole. This tiny pressure also hinders secondary air from entering so the mixture becomes very rich and reducing. Often really really small damper adjustments are made, like 1/16” at a time to fine tune this back pressure.

Double check the numbering on your cones. If five was tipped then 6 and 7 are hotter and will not be bent. If you are firing to cone 5 then a popular stack would be 4,5,6. Or guide, fire, guard if you will. The operator would see 4 begin to go down which was a guide or warning that things are close and observe until 5 goes down. That should leave cone 6 still standing. IR rated glasses can be purchased online pretty easily and IR 3 or higher are often suggested. Regular sunglasses won’t cut it kilns produce infrared not UV rays. Protect your eyes.

The last picture has the model number on it. A bit blurry but max temp looks like 2000 degrees (cone 01) so probably not a kiln for clay. Search paragons website for the model number ….. or post a clear picture of the equipment tag. The DTC 800 is the model of the control. Is it tropical where you are located? If the craftsman is still with us, I would ask him what he used it for as well.

Put the headphones on and sounds like a worn bearing or belt. The squeak when turned on and off is a bit odd as well. I would definitely get a better video and audio before the drive. A steady one showing smooth operation from zero speed to top speed using the foot pedal. Maybe they could turn off whatever is blaring in the back ground as well.

Could be but my guess is pore water migrates with time as the surrounding air becomes very dry and the kiln will will go through 240f at some rate anyway. In the end whatever you have success with, but I do remember the benched firing schedule with the quartz inversion hold. After probably millions of firings automatic controllers seemed to have made a good case that quartz inversion just happens, clay Is tough stuff.

I am with Neil, but maybe use a shelf on spacers instead of the brick to give yourself some space. The target brick can be 1/2 target and the Coanda effect will make 1/2 the flame wrap around the 1/2 target so a nice way to still get about 1/2 the capacity to the rear wall and get some energy and turbulence towards the front of the kiln. Since you are reducing so easily, it indicates not enough secondary air. The opening around your burner might need enlargement, general practice or to bell these or enlarge them so about 50-60% of your air comes as secondary air. Oxidizing firing would be 10:1 air fuel ratio. If you get your hands on an oxygen sensor you could tune this much easier.. Old Alpine designs used to include additional secondary air ports in the rear of their flame trench(s). It did even things out as their burners were fully imbedded in the kiln restricting the secondary air opening so it was sort of necessary. Just some thoughts for experimentation.

No I think I agree with pretty much everything said thus far. What I was asking specifically was : the vapor pressure of the water will be positive with respect to the local pressure, hence vaporization and it leaves by pressure, not necessarily quietly sits there evaporating. Calories are interesting also, but tying that to temperature presents it’s own issues.. My concluding question was how do we use this in a practical way? As far as understanding it with any precision I believe it is beyond practicall pottery which includes: measurement precision, local boiling point, pure water, porosity of the clay, thickness of the clay, energy available to heat, and so on …. It’s too difficult an issue for me so to candle below boiling is conservative IMO.

Hmm, interesting stuff so If I don’t start at freezing does it take less calories? …. And as it “vaporizes” is there any particular pressure associated with the vaporization? And finally how can this be used practically when drying wares?

Stain and clear matte likely should get you close and can be adjustable and repeatable. There are lots of clear matte glazes out on Glazy.

Like many machines that are rotation dependent and because of the type motor / power can rotate backwards for their use depending on the order of the phase connections. it’s customary to provide direction to the electrician on rotation and reversing it as appropriate so the machine is setup appropriately after it is wired. Reversing rotation is usually a simple matter of switching two wires which is noted on the machine. The manufacture often can’t predict the universal order of phase (a,b,c -r,s,t) so final commissioning is left up to the person connecting the machine. In other words being an electrician / mechanic also often requires latent skills. This is true for many industrial machines and even many air conditioning compressors. A backwards spinning scroll compressor just doesn’t work.

Sounds like a rebuild for sure followed by regular typical maintenance from here on. Interesting what the build up could be so pictures would be helpful. Hopefully not an insane amount of carbon else a change in firing habits may be in order to solve that problem. I assume these are natural gas or propane so please describe the fuel, model etc…. with your pictures as well as an idea of what the typical firing schedule entails (including gas pressure adjustments and damper operation through the firing) and how folks are achieving reduction without generating tons of soot would be helpful. Finally, there are still a few other things I can think of but pictures definitely would be a good step, include the burners as well if possible, maybe top down if possible. Last I checked Geil is still in business so replacement parts can be had. http://www.kilns.com/

Generally for typical domestic water type stuff loops, offsets, changes in direction allow the pipe to shrink and grow. Fastening specifications vary but generally allow uniform support and axial movement. Here is one of many guides out there: https://www.flowguard.com/blog/how-to-account-for-pipe-expansion-in-a-plumbing-system

Assuming these numbers are correct, when your element resistance rises by 10%, generally they are worn and need replacement and your kiln will not make top temperature. The design of many of these kilns (new) is 110% excess wattage to offset the shell losses. Wattage and losses drive the entire thing. Power or wattage = voltage(squared)/resistance. Power decreases linearly as resistance goes up but power decreases exponentially as voltage goes down. So a 5% decrease in voltage gets you approximately a 10% decrease in wattage. Add some shell leaks and you can’t make temperature. The numbers say your decrease in power is definitely a huge issue because of the depressed voltage. Is the wiring to the kiln adequately sized or does your mains voltage drop to 228v? Additionally, measuring the actual voltage and amperage at top temp accurately so we know the real hot resistance of the elements would probably reveal even less power is available as the kiln heats up. Your controller has interesting steps and droops in it as well which could indicate significant overshoot and under shoot while firing. The percentage on / off is all over the place so it’s PID parameters likely don’t match this load well. Seal up your kiln, but at that low of voltage I don’t believe you have enough energy. Your kiln is running on 10% less wattage to begin with.

I get 6100 w and some change. Is the graph true and it’s heating at a decent rate and just stops at the magic 1080c? Normally the SSR would be pulsed on / off by the PID logic to maintain a heating rate. At 1080c can you confirm it is on 100% of the time and the kiln does not climb? Also would be curious of the drop across the SSR just to understand how much power was being consumed by it. Easy enough to just jump this out and see what the firing temperature rate of rise ends up to be for real. Its hard to believe it’s moving upward in the hundreds of degrees c per hour and just quits at some point.

just guessing here so…… Hmm, so not enough power to make temperature vs the shell losses. 1250 c recorded for a 1260c kiln. Seems reasonable actually.but maybe the green line is the set point? Assuming it’s not even close, then why is there not enough power. Brand new at 5760 Watts this barely makes cone 8. So when worn roughly 10% it will no longer make cone 8 and requires aan element change. Assuming not enough power Do you really have 5760 watts? ( measured accurately) your graph does not show the firing rate of your SSR which is firing at some preset slope and never really changes if we do not include the green plot. The lid The gap will add to increased losses. The top and bottom of your kiln will account for the greatest percentage of losses, but this kiln will not routinely make cone 8, that is a max temp when brand new. light load The more wares, the more mass the more power it will take My best guess if it’s maxing out at 1080c but as your graph shows it’s progressing at 200-260c per hour then abruptly stops it’s likely a programming issue or SSR drive related issue.

Interesting the attachments are intact yet when the material shrunk it exceeded the strength of the clay rather than bend during shrinkage. Better clay, thicker form all possibilities but handles should also have a way to shrink and uniformly bend a little as they shrink. Simple C form handles are often great examples as the perfect C often will collapse a bit into an over bent C but the handle because of its shape takes a bit of the axial stress and bends along the spine of the handle. Without getting too nerdy, some handle shapes allow the distribution of axial stress more evenly. So stronger clay may be the answer but handle shape and pre shape are something to experiment with. As others have likely said, good practice throughout production and attachment are always important some handle shapes have a bit of an over loop at the top which can distribute this stress along the clay better than having all the force converge into one spot. A little illustration of how we allow for this stress in pipe work below. Very similar to a C shaped handle.

Sorry this has been here for a bit - just got back to it. This is not difficult so no worries. In general: bisque firings burn out all organics and to do that, the firing goes relatively slow (8-10) hours or even more for very “dirty” clays. What temperature (cone) are you working at and which JenKen controller / kiln do you have? Picture of the control would be helpful as well.

I have read through this and cannot tell if you are using witness cones to confirm things are “too hot”. Cones sense temperature but also time at a temperature or heat work. The target cone temperature built into the controller is a target which can change a bit depending upon the amount of heat work calculated. Often this depends on the load as well. The controller keeps calculating the heatwork which often ends on or near the target. Witness cones are the only way to know what the kiln truly fired to. In the end, the best firing for your clay and glaze is the one your glazes behave the best in.

I think I would opt for wiring the elements in series (high power) for each ring and feed them with their own infinite switch 240 v no nuetral. Fix up the sitter and use it to feed everything as a safety. Clearly remark everything for 240v operation with a ground. (3 wire). Just like more modern kilns that do not use a neutral. There are no 120v auxiliary loads this way so no need to run the neutral. The infinite switches will provide variability for firing. Safe neat wiring practices for load and temperature rating is also a must though IMO. 4 way switch below to give you an idea of typical operation. If you wire two elements in series they can be driven by 240 v without a neutral at their junction.

Just a quick reminder, for kilns in North America electrical is a bit different as in: the breaker needs to be sized for at least 125% of the load but no greater than 150%. NEC sizing rules. Secs. 210-22(c), 220-3(a), 220-10(b), and 384-16(c) Basically they are considered a continuous resistive load. A 40 amp breaker and wiring, if my math is right.

Just a first question, it is an old Paragon that requires 240v with a neutral and an earth ground. Do you have Two (2) 120v circuits and a fully rated Nuetral run to the machine? This should be your wiring diagram https://paragonweb.com/wp-content/uploads/A82B_A823B_A81B_A88B_AA8B_AA8B3B_WD_PL.pdf four way switch operation below requires both 120v circuits AND a nuetral.

Just a thing or two to think about: 30 gallons of water weighs about 250 pounds. The pressure on the cylinder walls will be dependent on the height of the liquid. (0.433 - about 1/2 psi for each foot). And of course the container itself will be the weight of the container plus the weight of the water so picking this up with two hands will place a lot of force where your hands are placed on the cylinder. Assuming 50-100 pounds of clay, this container full will likely be quite a challenge to pick up and move around.

And of course drying at home, but never in any rush with a temp hold there for sure.

Yes, I did not mean to make that sound negative, apology and it does seem very interesting so thanks for sharing. As you say, it definitely must save time so I would be curious how much? Again, I am just old and chicken, never gonna take someone’s full bust sculpture and not be ultra conservative - just me though. fyi I am not associated with any particular studio as well, I have unlimited access to several that I have helped over the years but they are hours of travel away.