Bill Kielb

She programmed 60c per hour and it does not follow that in the final segment of firing. See original post.

I think smart to check the elements but also, have you checked that they all are glowing and one set is not out? You did a lot of the hard work by confirming that the kiln was slowing down especially at the top temperatures, you reasonably verified the thermocouple is reflecting room temperature and proven as best you can that even when lowering the endpoint temperature from 1220 to 1190 the kiln still over fires because it takes more time than programmed. That you did these things is quite impressive actually, but they point to not enough power available at the top temperature. You can’t recalibrate or offset your controller to make it fire faster and you have already offset by 25c and only improved things slightly. All things point to reduced power or or an element not working, it’s logical now to test why you do not have enough power at top temperature. I think everyone understands that elements are expensive and are hoping for another fix including me. I think it’s time to find out why, hopefully you will find a loose connection or come back and tell us one relay was not working. Definitely make sure all connections are sound and in good order though, thermocouple or other. One thing we did not discuss and has been assumed is if it is operating at it’s required voltage so time to measure all that as well with your new meter. 1260c is cone nine, so this kiln ought to get 100 - 150 firings on an element set before it starts slowing down while reaching cone 6 temperatures and requires new elements. Generally 10% less power and kilns start to take more time until they simply can’t achieve a decent cone 6 glaze firing.

She programmed the last segment for 60c per hour but timing it realized it was off trac, not going 60c per hour and taking longer. So what we know is it could not achieve 60 c per hour once it got above 1170C, according to the OP tracking it. The kiln only exceeded time, not temps so far as we know. The cones reflect the heatwork which at this point appears to be the extra time spent during the final segment.

@Babs @neilestrick It was mysterious as her times and ramps seemed good especially at the end of firing, but when I asked if these were actual or just calculated she did watch this and explained: Hmm, I wonder if the elements are worn, as I set up a camera and checked the temp every hour against what it should have been. I found that the kiln follows the ramp spot on, until it gets to about 1170C and then it slows down, and added about an extra 15 mins to the total time” So it looks like she did the hard work and figured out the kiln runs out of speed at the top. I think worn or bad element connection, relay etc… is really likely. Recalibrating around one of those conditions is not very likely.

Your kiln appears to be 6226 watts or 25.9 amps, let’s call it 26 amps. 1/2 the power is from the top ring and 1/2 the power is from the bottom ring. So 26 amps/2 = 13 amps load on each infinite switch. The elements must stay in series (No neutral connected at this junction) and each series group gets fed from the infinite switch. H1 to one side of the element group and H2 to the other side. Sketch it up and post it just to be sure - folks here will double check. Notice a 40 amp fuse was required, today the breaker size is 125% of the load not to exceed 150% meaning 35 amps for todays breakers. This is a special requirement for kilns to make sure the breaker doesn’t overheat and wear out. You 30 amp breaker is undersized and this ought to have #8 wire run to it as well.

@Babs Hmm, not sure where this is going but if the kiln does not make 60c per hour in the final segment nearly empty it likely will degrade rapidly from there until no amount of extra time will make it work. If this is as it appears, calibrating may work for a short while but very likely won’t work on a full kiln. If true, It cant make a suitable rate empty, when full its rate likely will be unusable even with the best of recalibrating. Calibrating and compensating won’t make it fire faster at the top temperatures. All speculation though, And hopefully a minor problem like a set of elements out, bad relay, bad connection. I think finding out is the prudent course of action though.

@Dana StripeMost kilns will not do it. Generally a cone 10 kiln will get you 150-200 fittings at cone 6 before the elements wear by 10% or more and you simply can’t make cone 6 temperatures without a controller error or poorly fired glaze. Also your controller ought to be limited to 2250 peak temperature from the factory so getting to cone 7 would be tough. You have a rare performer. What model Skutt and how many watts?

This is great but I would encourage you to read the step by step guide from your state posted above its really done well. I think it will remove some of the scare factor. As far as accounting and taxes you will need to adopt real accounting practices regardless of the structure corporate or not so an accountant or your husband can make that a lot less challenging. Tax filings I always outsourced that, it’s not worth my time to learn tax accounting for various states.

Maybe, I think a clear picture and model number lookup likely answers the questions. Max temp generally means absolute top or design limit so firing to 1945 f (cone 04) probably hard to do if not brand new. A lookup of the model on Paragons website possibly provides the best info.

Generally a registering agent can be you, a company or a professional individual that meets the requirements of the state. Here is a good LLC guide to give you a better idea of the steps. Years ago I was an LLC in NC, among other states, very similar actually. https://howtostartanllc.com/south-carolina-llc

If it’s not making 60c per hour at the end then definitely check them. Actually no harm in knowing how to check them. Again though, make sure they are ALL glowing.. if one set is out because of a relay or connection it can also be a reason it slows down excessively at the top temperatures even though it was an empty kiln. If what you saw on camera and have been confirming with cones is correct, it appears under powered right now. How fast it goes in the beginning can be less material indication. If it cannot achieve its end firing speeds when it needs to have all power available, that is very material. The task is just to confirm why. Loose wires and bad relays, improper wiring are a thing. Make sure all elements are glowing as well, one of the simplest of things to check first.

Really interesting find and firing to cone 5 with a 15 minute hold gets you to cone 6 so firing with the equivalent of a slow rate, very likely gets you cone 6 or more. If that’s the issue, then the elements will continue to degrade and it will be very hard to get it to fire properly. Since your kiln was lightly loaded, If all this is true, fully loaded would make it worse. Generally when elements wear by 10% they need replacement so measuring to see if their resistance has risen by 10% or more from their new value is a good way to confirm. we are not sure all the elements are working though, so be sure they ALL are as well to rule that out.

I would suggest following the cone chart and firing the last 100c at the rate shown in the column or 60 c for the center column. If it fires too hot you can always drop to the cone 5-1/2 peak temp, still maintain the last 100c firing rate and dial that in. this is easy enough to do until you test a solid cone six. Oddly though things begin to over fire when the kiln fires slower than that rate. As kiln elements wear out, this does happen as their final segment where glazes mature actually is slower than the prescribed speed. Your calculations for the time are spot on, but is that what it is actually happening in real time? Finally thermocouple offsets are made for the occasion so it is possible that the thermocouple is incorrect. How accurate is it at room trmperature?

My vote: Katz class is great, and he is a derivative of Alfred University. Sue is a derivative of Katz, really like her as well and she has always provided a good deal of free content that I have followed for quite a bit. It’s hard not to support her, and she has taken the Katz model and added studio components to it. I believe Jessica Putnam Phillips still has a Zillion videos on you tube, participates in Clayshare and has developed some very ornate pieces, always pleasant to watch. She may have paid classes these days. John Britt still has a great online presence. Digital fire is still a great free resource. Old knowledge is still valid such books: Cullen Parmelee, Hasselberth and Roy, John Britt …….. all are valuable learning tools IMO. The Katz class in clay and glaze chemistry definitely is good to get early, it tends to help in perspective in my view as there are many many theories that run through the clay community.

There are a number of things that come to mind, but I would start with looking at results of strontium crystal magic and see if that fits the look you are trying to achieve. Here is a nice video with some samples https://youtu.be/56QFPsF2T04 you may find appealing.

Just some thoughts Sort of out of order and likely won’t stay put on cone 6 stuff. When things are bisque fired they sinter and not fully melt. They are a bit sturdier but not that great. Just curious if you intended to fire to cone 6 and get a very matte finish with your process. If yes, I am guessing the under glaze or in this case the stained body may have lightened up after firing hotter. If the guess is a yes, this is not uncommon and many manufactures provide some relative direction on what will happen to various colors as they fire higher. Some darken, some fade, etc…. Many sculpture artist I know fire their colors progressively hotter on test tiles to see where it no longer is artistically acceptable to them.

Yes, pretty rare but little critters have a habit of causing havoc, especially gas pilots where they often crawl in and make folks wonder what’s wrong with my gas kiln? Only way to figure out is with real stepwise troubleshooting. Good thing Bro was there!

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.