Bill Kielb

Generally electric kilns are rated and limited by the amount of electric power available and element life at their rated cone. With gas it’s really easy to supply lots of heating so generally easy to supply enough power to get to cone 10. So in general the fire brick is fine, just a rating geared toward the kilns electrical capacity to produce enough heat. Having said that these conversions are generally fine, but not the most efficient or sturdiest or the easiest firing construct of a gas kiln. But they are economical, educational and generally can service many successful firings.

I will just add, it may be possible to burnout any remaining stains with a careful firing to 800 degrees or so. Obviously lots of risks to the ware with all methods and non destructive or surrogate testing some way almost essential so you don’t ruin the piece.

My favorite clay detergent - Dihydrogen monoxide, best solvent I know of. Clay dissolves in it readily! Pre- rinse bucket O water, maybe rinse several times with rinse water allowed to settle before disposal. The problem with clay is the particle size are super small and fairly sticky so settling is realistically probably more doable than filtering. Detergents - not so much, water is extremely effective. Settling and proper disposal probably essential though.

You may want to take a look at sites like: https://suemcleodceramics.com/. Lots of free stuff to read as well as online work shops. More free and paid resources https://digitalfire.com/glossary/tony+hansen, https://glazy.org/kilnschedules, https://ceramicmaterialsworkshop.com/

Glazes almost always craze because they don’t fit the clay. Especially delayed crazing. I would say most likely that glaze does not fit the clay.

Just to suggest to try ending at the rate published in the Orton chart if you are using Orton cones without a hold unless you want additional heatwork to move to the next cone. So cone for cone 04 go 60 deg. Per hour in the last 100c. cone 04 from chart : 1063c Last hundred starts at 963c last segment = 60 per hour starting at 963 and ending at 1063. The final 100c of the firing is generally where things mature to cone and Orton has tested their cones to operate this way. Just following the chart may improve your results significantly. Edit: I should add here I would use the center rate or 60c per hour. Many kilns fail or eventually fail to achieve much higher, for which unless you are timing and calculating the rate, really messes with the correct endpoint. It can lead to what appear to be random results especially between bisque and glaze firings. In North America we have a popular automatic controller that actually detects if things are going too slow and will display as an error. So unless you are checking time and temperature for the last hour to hour and one half, it’s hard to know what speed it is achieving really. The 60 c column seems to be a more dependable ending speed most kilns can achieve with reasonable elements.

The answer can be no, especially if the kiln manufacture specifically defines the distance from combustibles as a minimum of 18”. One of the unknowns here is how hot will the space adjacent to the kiln be allowed to rise to? The radiation from the kiln will also warm the wood considerably. Fire engineering says wood can ignite in the 450 - 500 f range so I think realistically having combustibles close to a kiln is not best practice and the farther the better. But note, if this space is setup so as to Always remove all the kiln heat, then 18” becomes less of a risk.

IMO I would fire them unless you are convinced you have a way to remove the stains without simply driving them deeper into the shelf. It should be mostly carbon so hopefully burns away to a clean finish. Whatever remains if any should be very inert moving forward. I would run a regular medium speed bisque - 10-12 hours. It likely will disappear sooner but a full bisque run ought to pretty much burn out just about anything of significance.

These are the things that burn away in a bisque fire, so if you can sufficiently ventilate and given enough time and prox. 2000 f (1000c) the organics burn completely out.

Your problems are not unique. Here is a post I placed in a previous thread to show what can happen when folks don’t follow the requirements. The whole thread is worth the read as we see this time and time again from owners to electricians and even an inspector on occasion. What I have learned: Get the right size breaker, check all connections carefully, not just a once over.

Kiln Breaker Sizing, Code, Manufactures breaker recommendations - North America electrical practices Just thought I would post here, these things seem to come up often. Anyway ran across an inspection I did several months ago. The issue was breaker sizing for multiple commercial water heaters, which are very similar to a kiln load in many respects. Anyway long story short, in NorthAmerica breakers sizings are usually limited to 80% design load or for special continuous use resistance appliances a minimum of 125% of the continuous load but not more than 150%. This was created to keep the operation of the breaker in a typical panel reasonably cool and therefore extend the life and reliability of the breaker. My anNonimized picture and infrared photo below depicts the unexpected continuous run time of one of a bank of water heaters (over three hours). Anyway, the breaker was sized slightly under 125% of the water heater load but still at least 100%. The manufacture listed the maximum breaker size as 30 amps. The electrician used a 25 amp, stating it was enough. Anyway, I think my infrared picture in operation at over 133 degrees f and the fact that it tripped validates the reason for the code and manufactures generally conservatively follow that code. Additionally this code has true time tested proven merit so ignoring it or misunderstanding it can reduce breaker lifespan and elevate the hazard of fire. It is scary to think an inspector would not take the time to learn their craft. Codes are important, manufactures have insight into the engineering and operation of their equipment. Generally their minimum and maximum recommendations are well researched and compliant with code requirements. Sizing breakers for kilns seems to be a tricky thing. Sizing them smaller than the manufacture suggests is probably not a good idea as can be plainly seen below. Hopefully this post will be useful for someone searching in the future wondering.

I don’t have any easy solution but the RM1210b is rated for your work. I would call and ask them if some exchange is possible with a restock charge or……….the easiest way to convert. It may be possible to use the elements for the B in the 120v model, maybe some minor wiring changes and of course it will need to run on 240v. Unfortunately converting it likely negates the warrantee. Looking at the wiring Diagrams the only obvious change is the elements and their configuration.

What is super important on ANY of these designs is the mixing manifold which allows much more room air and only a TINY amount of kiln air. So much of a mix of room and kiln air as to keep the discharge airstream 120 - 130 degrees or less even with the kiln at top operating temperature. When I measured a conventional operating system I found the combined exhaust was 7CFM per kiln in a two kiln 140 cfm system.. So the 140 cfm capacity was really used up in maintaining the proper suction pressure with a true flow of 1/10th or less of the rated airflow. you can use an inline fan, but designing to ensure the fan does not overheat is a must. Inline fans need to cool themselves with the airstream. The video below is an example of doing this in a hybrid fashion where an economical off the shelf long life (super quiet) inline blower is used to provide above kiln exhaust and still have enough power to run the downdraft system as it was designed. So almost all room air from above the kiln which means the inline blower will always see mostly near room temperature air and a small amount of kiln air still mixed with room air using the old mixing manifold design. https://youtu.be/etpa2Pc9Hug?feature=shared So this does answer your question to the extent prox 70 Cfm per kiln is plenty and most manufactured fans come with self cooling motors so wasting the horsepower to maintain suction so to speak (only prox 7cfm of airflow) is easiest and probably more goof proof from an overheating standpoint. The hybrid system in the video just takes the wasted horsepower if you will, and puts it to use moving air.

Just in case while you are waiting for recommendations. I think Google can be your friend here with a search such as dry glazes and pottery websites.

Generally affected by damper and speed Reduction flame will be yellow, very inefficient so if in reduction it ought to be going slow Lp tanks have hundreds of psi so two stage regulation to get down to 0.25” which is very small, pressure for a kiln that likely is intended to operate at 8”-14” maximum. You are firing propane, not a whole bunch of blue flame available really. Definitely not like natural gas for sure. so lots of things seem a bit amiss. I suggest pictures of everything we can see: operating gauge, operating valve, regulator(s), burner, burner orifice size, damper, flue height (approximate), how fast do you go in degrees per minute or hour, what speed are you trying to achieve, etc…. From there we can see how this kiln ought to fire then discuss typical reduction techniques and flame coming out of the spyhole, etc… right now many things you are experience seem to contradict the physical world. Not saying it is not acting up, but I suggest a good baseline would clear some of these things up.

You have measured the operating voltage and that is great, but we really need to know the amperage to calculate the wattage. These measurements really take place around energized conductors which requires solid electrical safety practices. I would suggest having someone help here - someone who is used to measurement of live circuits. I really hesitate to suggest more, additionally this kiln could be of an age when asbestos insulation was fashionable. For me, you really need the help of someone local. Any chance you have someone who could help?

Agreed, my observation as well over time. In fact the Marcia’s matte above is a clear matte and becomes clear glossy with only the addition of silica. It’s part of the exercise to show that a true Stull matte will go glossy based in the Si:Al ratio, all other components remaining the same. Definitely not saying it can’t be, but if so …….. likely under specific conditions.

Ceramic not the best for conduction but high temp. Air gap is essential and anything to block the radiation from the kiln (Shiny reflector) very productive. Kind of like the difference between blazing Sun and shade. If you mount it external, no need to come up with special hardware.

Fuses will not protect against human contact with energized parts. Fuses to protect SSR’s are very fast devices and SSR manufactures provide a way to calculate or specific requirement based on time to blow. Crydoms SSR protection: https://www.digikey.com/Site/Global/Layouts/DownloadPdf.ashx?pdfUrl=D8008051EDDB4C06A22AE4C371BFBECE It’s good to explore and create new things, unfortunately the things you don’t know carry the potential for fire or electrocution. A controller such as Neil mentions has a lot of engineering and safety built in and 12v kiln relays are economical, established performers and relatively safe.

Looking at your drawing, I would say no. You are leaving the sitter in place which is a good idea for safety …. Still use cones. The SSR’s would typically take the place of the three heat switches. Since SSR’s can get stuck on as well as off a safety relay is usually placed before them and enabled by a safety circuit. Additionally PID’s work but can be difficult for most to program. Neil is right about design, cooling, and fabrication. If you are not familiar with kilns, SSR design, fail safe operating designs and electrical wiring practices this might prove to be a huge challenge. Using a manufactured kiln controller might prove easier in the end and provide a more pleasant operating experience with built in safety features.

Not the greatest pics and all test bowls I could lay my hands on. The one on the right was from a no drip lip video so thrown and test decorated in a hurry, ended up using it for years. Always ground with a diamond pad very smooth. Paranoid of scratching someone’s furniture.. They actually evolve from right to left where early on more pronounced foot and later (Left) minimal and always glazed inside these days. Unless it is an intended feature I like a minimal foot ring. Of course having glazes that don’t move is super helpful. Funny all of these quick thrown “test bowls” ended up as something very useful on a daily basis for us.

Definitely agree with all above but the simple answer is fiber or even rigid fiber generally perform better per inch than IFB. So to replicate or exceed what you have in fiber you need as much or more insulating value per inch as your IFB. Generally even rigid fiber thermally performs better and has less mass so less energy heating the bricks. Since fiber is not very structural, supporting the elements tends to be a functional issue and fabrication becomes a challenge. Just to mention, you may have a typo in the wattage posted. The size must be fairly small to fire quickly. One method is to build it with fire brick and wrap it with rigid high temp fiber to reduce the losses further.. Done correctly, you should be able to increase its size but reduce losses enough for it to remain a low power consumer. some material comparison below, comparing the conductivity per inch should give you an idea how thick to make it. Notice at the top temperatures, fiber begins to behave more like IFB.

My experience, the last 100c of the firing is where the heat work mostly is. If you look at the Orton chart this is specified for different ending speeds. So firing by cone gives a repeatable amount of work and I would argue very important for consistency. Having said that, there are folks who fire by temperature and figure out what works for them. Soaks or holds to me simply add heat work so I am curious to how much. Having said all that, the firing schedule before the last 100c is not as important to the melt but driven by ware thickness, moisture etc…. Some schedules from the Bartlett controller (many many kilns use this controller) and an excerpt of the Orton cone chart. You might find these useful. Sorry the Bartlett is in degrees f for rate, although zJohn Britts may have been as well.

You have it right, the manufacture has it right, the inspector has it wrong. Interestingly a 60 amp breaker is the minimum allowed. Breakers that you buy for home are usually rated and thermally limited in load to no more than 80%. 80% of 60 amps is 48 amps. Lots of folks know the 80% rule so if it dawns on him he may suddenly change his mind. In the end your electrician has it right and can point him to the NEC and NFPA requirements for a continuous load - resistance heat. Basically not less than 125% nor greater than 150%.

That’s the one - amtalc. It looks like 20g of silica gets you near 7:1 which progressed from very matte to satin to gloss. The recipe was made to dial in a level of desired matte / gloss just by raising the silica, just because everyone has a different concept of matte / satin. The excerpt above looks like it finished testing at 20g / 100 as glossy enough to finalize the progression and results. You likely could go higher as well, just never went any further and not intended as a gloss glaze. This clear along with Bills hard candy clear (high gloss) were a pair of glazes developed with additional boron to eliminate issues over heavy underglaze and certain underglaze colors. The additional boron seemed to help a great deal and allowed the brush artists freedom to paint, layer etc…. It was tested at cone 5 and appeared to melt well, never lower nor its upper end. It is so stiff, it never moved for us but was used at cone 6 with good results.