Bill Kielb

Yes, this is a good thought. I was just often in the situation to get asked and then I was in a bit of a dilemma. I guess I would say one’s perception is affected by experience. Any studio I walk in ………any ……….. home or commercial I see kilns have been under insulated for so long that we have surely wasted mega watts of energy globally. Reduction firing, let’s generate more CO! Wood firing, not sure anyone can argue anything environmentally good about that. Glazes that waste natural resources, soda firing, mining products….. The list goes on with respect to sustainability and outright environmental damage. I had a colleague point out oil is renewable, just not in our scale of time. She is right, but not a reason to keep improving what we do. I think the best one can do is encourage others, lead by example don’t let it get to you. Remember we are always learning so the things everyone thought were key yesterday may change a bit tomorrow. My food pyramid flipped upside down I think. Why isn’t it mandatory to plant X number of trees every time one wood fires? Just kidding, it’s just a suggestion that I think might make sense rather than try and stop all wood firing.

It’s been so long, the only thing I remember is the aggravating pinholes and premixed glazes that were ridiculously thick on occasion. What I do remember is we always fired to cone 6 which in the end seemed a bit hot for some of the Amaco glazes especially adding a soak. Their published firing schedule is a fast ending segment of 270 degrees per hour in the lasts 200 degrees putting them at Orton cone 5-1/2 to cone 6. Most of our kilns fully loaded could not achieve that speed at the very top end so even more frustration. Good or bad It drove us to learn more about glazes and abandon all the commercial stuff.

Just an add I have entertained this theory and I think he wanted to call it “packed bed porosity” as I recall. A nice theory that may have value, but I have never been able to confirm with confidence in several trials.

Interesting, my first experience with pinholes in glazes were with those very glazes, I believe. So much so that I decided to learn a bit about glazes. Mark has found a solution for his, so definitely test that. What I can share is some glazes will actually pinhole more the hotter you make them. For these compositions, the drop and hold firing schedule seems effective. Digital fire has a decent bit about this. For glazes affected this way a common thought is by composition their fired surface tension does not allow the pinholes to heal. For those, dropping temperature a bit allowing them to thicken slightly and holding allows the glaze to flow back together and heal the pinholes. My first experience with oatmeal was super frustrating with top end soaks and holds which for that glaze / clay combination made things worse. If a top end soak or hold seems to make things worse then I suggest reading about and trying (testing) a drop and hold schedule to see if that works for you.

Good catch & bad math interesting, does this fire 30 cy on and 30 cy off at 100% output?

Yes I believe they will be just fine. They are zero crossing so the fastest they can be commanded off or on will need to wait for zero crossing. I think the default for typical heating controllers would be approximately 200 milliseconds ( so 2 seconds, something on that order). The default typical fastest for kiln relays (if my memory serves) approximately 10 seconds. Measuring the amperage of a resistance load by ct ought to be fine especially at maximum output. I think your idea is fine and reveals the heated resistance as well, I am a sequential troubleshooter so any data with integrity is helpful to me. Not everyone troubleshoots in the same way though. aTo your other point about duty cycles, yes …….. and the controller generally is set to compensate or even things out using the top or bottom element to help the middle. That the kiln actually stalls is very interesting to me. It has potentially symptoms of several faults, yet everything has tested good. My take, I need to know some real values, thermocouple type, wiring sequence ….. something is wrong but without real confirmation I cannot speculate.

Without pictures, real measurements, response to all that’s been asked above, I think this will be difficult to solve.

Other trick that comes to mind for spraying. Spray even coat, gently pull the trigger 1/2 way (air only) and gently dry what you just sprayed. Future coats same procedure building up the thickness and drying each until it’s thickness is similar to a freshly dipped pot. Usually two to four even light coats. Dry each coat in between before applying the next. This works well over heavily underglazed areas on bisque ware as well and ensures each layer is applied evenly. Heavy underglaze often changes the absorbency locally so drying these areas before the next coat makes applying glazes evenly a snap. Definitely waster slabs under reglazed pots is good practice. Spraying allows for multiple even coats and is similar to preheating. You are trying to speed up the drying process in both cases.

Just curious - Are you trying to sub the boron through Fritt or are you just eliminating the boron

Yep - I think any readings and even pictures would help here.

some of my experience Thickness will help, but you may be able to design around it depending on what is collapsing. Larger diameters if you will instead of tall and slender can enhance the strength. Horizontal shoulders collapse but gradual thickening inside can allow the force to distribute down into the sidewall clay on axis rather than a cantilever shoulder. So when practical select thickening of areas is definitely a thing for me.

I think it’s possible the zoning might not match which would act very strange unless in single zone. So can we be absolutely certain the relays are wired in zone sequence? High voltage (element) wiring to the relays but also the relay control wiring to the controller. I have on occasion seen these switched after a rebuild. Just switching 2 could create an issue. Also I do not see a type S option for thermocouples, so maybe so but worth checking.. If you have K and it’s programmed for S or even vice versa, this would lead to very odd firings. It’s super important all these match, meaning the software programming and if a jumper is present they all match the actual type. What color are the extension leads that attach to the control board? Type S most often black and red, type k most often yellow and red. Can you post a picture of the thermocouples and maybe several context photos of the kiln open with the wiring going to the control and elements. Maybe more eyes on it will spot the issue. Finally, what do the elements measure in ohms as exact as you can measure. A different alloy will very likely show up in this measurement but the measurement needs to be reasonably accurate and confirmed.

I see open wire connectors laying in the bottom of the tray, couldn’t be that simple I suppose. What have you tested already and how?

You can test it but need to extract and hook up through a 10k ohm resistor and a 9v battery. Forward will give you .6-.7v across the junction, reverse should tell you the breakdown voltage. If it’s shattered and you. Find a similar color coded zener in the circuit then you may be able to test the good one to get an idea of the rating. Almost forgot to ask, does it run at all? Trip breaker? Can he measure the breakdown voltage in circuit as is?

I can add, 20 amp generally better than 15 amp rated. If they trip though (not from self test) there is almost always leakage beyond allowed so is it a nuisance or is it just telling you there is leakage? Generally the device being powered has a small amount of leakage to ground. All the more reason to make sure the shell of the device is well grounded, GFI or not.

Yep, personally any receptacle located near water, any operating wheel. Fire extinguishers - yes, checked and renewed yearly, for personal use, quite a few life safety additions as well. Good question! My experience if a gfi tripped there was a reason for the leakage I need to figure out. Commercial Two fairly large studios I have friendly access to - all have a bit more required commercial health and safety items: GFI’s as described above, both have fire extinguishers located throughout. Many I helped the owner install including code required: extinguishers, tempered hot water to 120 degrees, battery backup exit signage, emergency lights, night lighting, real ventilation for spraying, real extraction for glaze composition, real designed combustion air and ventilation for occupancy ….. quite a few requirements they benefit from whereas at home one is sort of free to pick and choose. GFI and fire extinguisher probably the minimum though.

This is interesting in the design of top and bottom elements are prox 6400 watts and the center is prox 5000 watts (as expected, most loss at top and bottom and they assist the center) but the experience is the center is not firing as hot. I wonder if the zones are out of sequence with the thermocouples, board connections or even the relay wiring. In addition to resistance I think I would make sure the zone sequencing is absolutely correct. IE zone 1 tc = zone 1 = zone 1 relay and elements. Cross firing (or a really really bad center element) is a potential reason that would explain the center to be cooler. Very odd! Positionally it would be hard to mix these up and get the current result.

@MochiFriend Just in case you end up in the garage, years ago we helped with a system (very low cost) that would allow studio users to fire in an enclosed dock. Not totally pertinent here but maybe helpful to look at the intent to intercept the various sources of air without overdrawing them but still ensuring the room was reasonably negative with respect to the studio. The carpet blower was an ideal economical high power blower that needed to be in place and operating during firing. Marcia Grant ( my Marcia) was nice enough to sketch this so it would be more understandable for the folks in the studio. Anyway - a nice sketch with some well illustrated terminology for the various sources of air, might be useful for perspective for others here or for you if you move to the garage.

Sorry did not read the whole thread above…. Of course you use cones! Just a thought, some glazes will pinhole and not heal well when fired hot. Counterintuitive, they do liquify more but don’t necessarily spread out and heal as one might think. Drop and hold is often an effective way to get these types of compositions to heal. I also assume you are firing cone 8 because it matches your clay and glaze maturity requirements. If not, firing too hot can have its draw backs.

just an observation The 20 minute hold likely gets you to cone 7, not sure if that is what you are trying for. Do you use cones?

@MochiFriend If this is an older monitor I would definitely check the pm2.5 module. They generally allow gentle cleaning of the optical detector and pathway. It’s really unlikely to have such low readings, especially when outdoor air is usually in solid single or double digit range. 2.5 micron stuff is really small to the point where a reading of approximately 300 would show as very fine dust in a beam of sunlight or laser pointer. Generally Everyone has to dust, even folks with 1 micron hepa air purifiers. So a count of zero or one seems relatively unlikely. Still you have VOC’s so the trend and delta readings super helpful to illustrate the point: it’s hard to completely ventilate a kiln indoors, and to be as effective as practical it’s often really hard for folks to do without some solid formal experience. While much advice is well intentioned, it ends up a bit more non intuitive than expected. Picture below of me verifying that no matter how gently one scoops glaze chems out, hundreds if not thousands of very very small particles get displaced and migrate tens of feet or more, nearly instantly. The laser is a nice visual example much like the beam of sunlight. Finally a personal thanks for sharing, this is a hard subject to address to the level in these threads and yet could help a significant number of potters have a better understanding of the dynamics present.

Sorry for the confusion, as long as you have enough volume in your house the makeup air from all the little cracks etc… likely is fine as you have run the dryer without issue and it sucks about 200cfm out of the room when operating.. So with the window closed maximum draw will occur from all other rooms which will limit the fumes from exfiltrating to the occupied spaces. If later, running the kiln vent, bath fan, stove vent etc… the volume of your house and normal leaks may not be enough and you will begin pulling from your furnace ….. providing your furnace is a natural draft furnace. Anyway, two competing issues, pure ventilation and combustion appliance makeup air. Always safe to design in makeup air so combustion appliances behave well. So not a one sized fits all and best done by someone with experience and knows all the components of the home else out of safety you will likely see makeup air always suggested. Like most things if someone is viewing these problems as a stream of airflow, technically this is usually a very flawed view. Folks who do it everyday for real are very cognizant of the pressure difference. Interesting results from the air monitor btw. I see a lot of general assumptions about vents, kilns and working near them, this may be a nice simple way to show folks All the fumes are likely never captured by down draft ventilation. Your pm 2.5 results seem low since outdoor air is generally above zero. Regardless a nice indicator of trend and your monitor does voc.

As a suggested test I would take one piece that is very intact with no defects and fire to cone 5, not cone 05. Your clay and glaze are midfire, not low fire.

I think I would be very pleased to know the segment rate and after observing the delta graphically (or numerically) over time I would have a decent sense of how fast can this kiln go with reasonable accuracy and it would also be a strong indicator of element condition at peak temperature for me. Maybe less complex would be best for me and at a glance indicator of trend most useful.

When you run the dryer it exhausts 200 cfm, window open or not, so no, air will be drawn in from the many minor openings in the house. Opening the window even a very small amount will help ensure that you do not suck fumes back down the flue of a gas fired appliance though. Most old codes allow exhaust by volume …. if there is sufficient home volume to draw from. Most homes have leakage on the order of 5 air charges per hour or more. I would suggest you put your pm2.5 in the adjacent room(s) to get a pretty good idea if you are succeeding in exhausting all the particles generated by the kiln from the kiln room. Maybe confirm by noting the reading in the room vs the reading in other rooms. If the fan is large enough exhaust then the other rooms will remain at or near their baseline and change proportional to the activity in the other rooms as well as the pm2.5 outdoors. If you are a smoker, the counts will be crazy high maybe up to 1000 µg/m3 or more especially when you first light up. outdoor air will generally be in the single digit range for pm2.5 but can rise very high due to fires for which air filtration became one of the only ways to lower this count indoors. Your local weather station likely posts AQI and maybe Pm2.5 daily. For my location today, at this point they have measured in the last hour AQI of 29 and pm2.5 of 8 µg/m3 See below accuweather prediction for my location.