Bill Kielb

From what I can see, these tests appear to not report false positive below 1mg / cm2 with 95% confidence. I guess we need to define “trace” amounts that would constitute not having lead. Some info from the EPA https://www.epa.gov/lead/hazard-standards-and-clearance-levels-lead-paint-dust-and-soil-tsca-sections-402-and-403 Allowable levels of dust are fairly low with an emphasis to not aerosolize lead by heating, scraping etc…..

Looking at the name plates and following NEC for continuous load: The 115 volt kiln should be a design resistance of 4.25 ohms so correcting for the present 120v supply 120/4.25 = (Potentially) 28.2 amps. Min Breaker size: 28.2 X 1.25 = 35.29 amps Max breaker size: 28.2X 1.50 = 42.3 amps The single phase kiln = 40 amp single pole breaker, associated rated: wiring, cord and receptacle. Wires= (1) line, (1) Neutral and one ground wire. The 230 volt kiln should be a design resistance of 11.5 ohms so correcting for the present 240v supply: 240/11.5 = (Potentially) 20.87 amps Min Breaker size : 20.87 X 1.25 = 26.09 amps Max breaker size: : 20.87 X 1.50 = 31.31 amps The 230 v kiln = 30 amp two pole breaker, associated rated: wiring, cord and receptacle. Wires= Line 1, Line 2 and one (1) ground wire, No Neutral. Have your electrician double check all of this and confirm. Common would be a three prong cord end and matching receptacle with the appropriate amperage rating.

@Hulk is spot on, post the design electrical requirements for best answer. Absent that, since you have an electrician coming, sizing for kilns comes under the continuous load definition for resistive loads meaning breakers sized for 125% of the load, not to exceed 150%. The potential problems would be the kiln was designed for 230v nominal system voltage so at 24p v it now will draw more amperage. Best way to know this is he should measure the resistance of the over all kiln load and adjust his breaker and wire size accordingly (still a continuous load under NEC) at the new system voltage of 240 volts. Second issue would be to confirm it is 240v 3 wire, meaning L1, L2 and a ground. If so, then the GFCI 50 amp breaker shown likely needs to be replaced because it will not have a load carrying neutral and the wattage at the higher system voltage will likely require a breaker rated higher anyway based on continuous load of its actual wattage. Best to post the design rating of this old kiln though as it is hard to speculate what the nameplate says.

Just some things that strike me For cracks happening at bisque, I would look for production techniques and handling prior to. Grog has never really helped me develop much extra strength. It generally Does open up the body. So cracking at bisque when the body is just being sintered maybe very telling For production I would always start with compression, real compression not just pushing down though. For bottoms, out to inward ribbing, not so much in to out …….. rims - ok, push down ……… walls - ribs are great. I would also not over work during the trimming stage, hard to do with lots of grog, I get it. Are we adding grog for appearance and is this creating weak areas for cracks to originate? Well mixed - homogeneous? Gently ring your bisque, often hairline cracks can be discovered at this point. For firing, I would definitely make sure it was constructed well and for sure, make sure it can slide easily on the kiln shelf which means silica or alumina or something to let this grow and shrink in all directions. In its present form it looks fairly rough maybe due to the grog so getting this right might take some doing. Your last picture almost looks like there is a shelf pluck mark, top right. it would be great to examine the bottoms of all these to see if the rough multiple foot rings likely contributed to some of the failures. I would start with the cracked bisque though, this may be telling you something.

I think in the states 1mg per cm2 for surface transfer limits so test kits are likely to detect in this range. Correlating surface transfer to absorption likely extremely difficult though. I am not aware of any amount of lead though that folks would say is fine after polluting the whole planet with low levels of the stuff. The argument at that time for a time evolved to is it is such a “tiny amount” …… See link above for an interesting accounting IMO

Definitely retest. I am very familiar with removing lead fouling from bores but do not have any idea why the Neph. Sy solution would work. Have heard it before, are you aware of an any citation explaining why / how this works? There are clay and glazes made with Neph. Sy btw.

Just noticed, the rotation arrow is on the sticker on the fan. It indicates rotation I described above. Set your motor rotation to match and you should be good to go with original mounting per the instructions.

It looks like a fairly straight bladed fan, so if rotation is wrong then it will blow in the opposite direction. Sort of reversible like a ceiling fan, check rotation for sure as your original mounting should have been fine. Just from the pictures, looking straight on at the BELT END of the fan I think it would rotate counter clockwise. Looking at the BLADED ENDI believe it should rotate clockwise. The fan should have a rotation arrow on it somewhere.

If it has a dc motor (and very likely has) then super likely you can just switch the motor leads positive for negative and negative to positive to make it spin opposite. Once confirmed, with the addition of a simple switch it’s usually possible to make this selectable more easily. Post a picture of the motor label and as much wiring to it as practical.

First idea that hits me, which model exhaust is yours and is it set up for 115 or 230v? I agree 1700 + cfm will seem to suck the chrome off a bumper. The air gets sucked out of the spray booth so if all else fails if the motor is blowing in, you will need to flip it but I believe you have it right. Motor drive side is the inlet. Now to use this you will need to let fresh air into the house somewhere. A lot of it!

It depends on the load. So cone 5 with a fifteen or 20 minute hold is a common one to get cone 6. If your cone is 1/4 the way down, closer than you probably think. I would start with 5 minutes and work from there. Once you reach 3 o’clock it’s not far off.

I agree with Neil, lots of your measurements add up perfectly but the amperage doesn’t lie. So at 27.4 amps best case at 240 volts solid - it is 6576 watts. This kiln needs 7200 watts to just make cone 6 a hand full of times in new condition. So, the only conclusion can be: while hot, the element resistance goes up a bunch leaving not enough power to make temp. I added a drawing below detailing where I would make measurements. The key - 30 amps going back to the panel. You don’t have it, you have 10% less, you won’t make temperature that way. 2021 is a bit of time, all firings wear the elements a bit, especially the high temperatures, so the elements ought to be worn by now. As far as ratings go, I wish they designed kilns with more spare power but maybe think of it as you have a car, absolute best case, the engine at its very highest RPM can just get you to 140 MPH. Top speed is officially 140 MPH! How many times do you think you can do that without damaging the engine? It’s just not designed for sustained service there.

Since this was empty, I think Neil’s point is very relevant. I think you will need to load the kiln and test. I mention speed because slower generally means more even so given the choice between 120 and 108 per hour (Center column Orton chart) is a good way to get predictable heatwork…… it is slower than 120 degrees so will tend to work more evenly across a single zone kiln. Almost all the heatwork takes place in the last 200 - 250 degrees, prior to that, generally everything is reversible. Slower heating tends to even things out. At some point all burnout has occurred so leaving the top plug out the entire firing can cause extra losses / extra energy use in the top section. Automatic cone firings tend to compensate for varying firing speeds and attempt to slide up and down the Orton chart depending on the speed the kiln can achieve for a given load. They can be helpful.

Yes,, I think it is! 60 degrees in the last 30 minutes. Bad math! 120 per hour more reasonable, maybe even a touch fast actually for evenness. Interesting, that makes more sense especially if an empty kiln. I wonder if that is slow, Medium, Fast cone fire? still want to know loaded or empty and if the order of the cones are correct. Expectation would be cooler top, then bottom, then middle based on radiation and convection but no way to know the element position / apportionment. That graph is a bit odd though 14:58 - 15:18 (20 minutes) = 60 degrees. Not sure that data is accurate.

Can you post the schedule, in this graph for the last hour or so it is firing on the order on 50 Degrees f per hour which seems be a bit odd for a cone fire schedule. The typical way would to hit a cone would be to fire about 100 f per hour for the last 200 degrees of the firing, so this seems different. Also can you tell us if this kiln was loaded or empty and why the top peep is out till the end of firing? Finally i assume this is top, middle, bottom left to right so do you have a shelf and spacers on the bottom of the kiln?

I have seen matte questions a bit here so …… Just noticed this came out! So posting it here in the event you are still working on these. Sue does a great job of explaining and providing answers to the question: How do I make a matte glaze / more glossy (Stull matte anyway) ? You might find it worth the read https://suemcleodceramics.com/how-to-turn-a-matte-glaze-glossy-with-one-ingredient/ She does mention other mattes and also provides good insight on under fired mattes etc…. IMO

Same here. Seems fine to me btw

Can you post a picture, the brushes should be spring loaded and slide in and out relatively freely. The brushes make contact with the commutator and it is possible for it to corrode and cause irregular operation. Likely one of the last things to expect but since you have indicated they appear to be corroded and do not slide in and out freely, they likely are corroded. Commutators corrode but are cleaned off by repeated use so when laid up with no use over time this can happen. If all else proves good, then removing the commutator corrosion and brush housing corrosion may be necessary as well as a motor rebuild to remove accumulated carbon from the gaps in the commutator and any rust that may have grown on the other iron parts in the motor. (Armature and stator) Anyway, hopefully not an issue and a last resort as this generally would be best rebuilt by someone who has experience with small electric motors. A little about cleaning a commutator https://youtu.be/yV4B-bN814g

That pretty ugly, even I would think twice about fixing that one.

If that spec is right, this kiln is specified for China paint and lowfire use so it may not make for many cone 6 firings before the elements need replacing. Neil is spot on though, you measured 15 amps for EACH element set or the kiln is drawing a solid 30 amps on each leg? Also, when heated, does it drop to 12 amps per element set as measured before?

Cone 04 Would generally be achieved by firing to 1945 and for the last 200 degrees of the firing, fired at a rate of 108 degrees per hour per the Orton chart. Now if the kiln failed to go 108 degrees per hour or at least reasonably close to that speed in the final 200 degrees then heatwork accumulates with time fired. One of the tricks often used is to fire to a lower cone with a hold to get to the next cone without increasing temperature. So firing to cone 5 with a twenty minute hold often gets 6 cone to drop. The 20 minutes of additional time added to the heatwork and melted the cone 6 cone. since you were firing at a very slow rate and likely for quite some time, your cone reflects that and likely is showing you that it fired beyond 04. When elements wear out sufficiently and as it takes more time to fire, usually things begin to overfire due to accumulated heatwork or the extra time spent in the firing.

Maybe 15 amps per element set? That would make more sense, then truly measuring 12 amps each that would indicate the elements heated - have risen from 16 ohms to 20 ohms per set. Accurate measurements would be key here as this is not enough power and points to worn elements. Bad contacts, bad connections still in play as well. I would start with an accurate measurement of cold elements. Each set should be 16 ohms. At 17.6 ohms they are considered worn so a decent meter is important.

At 12 amps@ 240 volts thats 2880 watts. Not likely you can get very far with that amount of power. Is this kiln built for China paints and lowfire work? Can you post a picture of the equipment tag so we know just what this ought to be? Just looking quickly at these models, even the tnf 82-2 is 30 amps, 7200 watts so it would need to be on a 40 amp breaker and appropriate wire. That would give it a total element resistance of about 8 ohms. Not sure the model I picked is yours though. Equipment tag ought to provide clarity.

A pyrometer is just something to measure temperature and display it. Many folks make them. Can you post a picture of the part you wish to replace in the event it is a kiln control.

Post a picture of the inside. All else fails Euclids can wind new elements. Depending upon effort and or cost and your needs, the question likely is do you want to sell it or use it?