Bill Kielb

Btw - very hard to do this without enough load to drain away the leakage, especially with a typical VOM. SSR’s have forward voltage leakage.

It’s a 12 vdc relay, try and find out the cause of the 16.5 v reading. If the mechanical relay failed the continuity test and the meter tested good, the mechanical relay is bad. 16.5 volts if true will shorten the life of the mechanical relay, definitely check the transformer installed wasn’t errantly installed using the 208 v primaries.

@cadenrank 16.5 vdc for control voltage is high especially for 12 vdc relays. Check your meter or check the power transformer is jumped for 240 not 208 v. If it’s correct measure between ac1 & ac2 for 24 VAC and then between ac1 to the center tap = 12VAC and ac2 to the center tap = 12VAC. All those values ought to be within ten percent. Careful they are AC values from the transformer. The control board should change the ac from the transformer to 12 vdc, so there is a chance your meter could be off, or the input voltage to the board is high. 12v relays will heat and wear faster driven by 16.5 volts so let’s make sure that is right first. To (for sure) test the mechanical relay which really only needs to have one bad leg in this configuration, remove the power from the relay, turn it on so it is closed (make sure 240v power (both legs) is disconnected and safe from the input of the relay) and measure for continuity. Measure the relay input to output (across the relay) it should be zero ohms for each leg. If any leg measures higher than 0.1 ohm, it’s defective. Failure of either side of the relay or both will cause the kiln to simply not work as the elements are configured in series so without both phases, they just won’t work. To triple check, temporarily (and safely) jump both sides of the safety relay respective phase inputs to their outputs and confirm the SSR fires the elements. Please Always use appropriate caution around ALL live electricity. If you were to operate the machine for any length of time in this jumped configuration you would need to unplug the kiln before ever loading or unloading because of that SSR leakage issue and the potential to shock the operator. The SSR will have some leakage so you likely will measure some voltage even when it is off. With a very high impedance meter this certainly can measure in the double digits. It sounds likely the mechanical relay will test as failed but the 16.5 vdc is really too high so figure that out regardless. Since leakage on the SSR is hard to test, to test the SSR (when this is all working again), during operation measure the high voltage across it In the on cycle it should read zero or very near zero (record what your read) in the off cycle it should read line voltage. I have to say single SSR made possible by series elements, single zone. I think a bit disappointing for an initial impression for me.

Just to add, much of this will end up to be surface observation. Does the glaze melt fully and for instance does it appear uniform and thick enough for 100% coverage. Sort of subjective but also can be obvious for glazes that are applied too thin and end up rough to the touch. Glazes not fully melted that should be gloss but are more matte. Observing the finished product often reveals whether the application thickness was appropriate for the glaze as well as whether the firing schedule was appropriate. Test tiles created while varying coverage or schedule usually reveal a best or minimum application, best schedule etc….. absent any glaze defects like crazing etc… generally visual observation and correlation to how the ware was prepared.

Lots of very course belts (They clog rather quickly) and lots of paint booth exhaust ………… and ear protection for sure. Belt sander made it ok, kind of normally used in a dusty environment anyway.

Funny you mention, right here locally in Illinois. Used to go there as a kid all the time. Last trip (40 Years forward) was a few years ago to pickup cheap dental tools for ……. Carving clay and some cork stoppers someone in the studio needed for their clay project.

I belt sanded a bunch absolutely clean then started using Lees. Lots of dusty work, bonded nitride from now on!

If you look at several of the successful recipes you will find a great deal of similarity with calcining a portion of the clay to reduce shrinkage. I think Sue McLeod has nearly the same recipe as above but does include some silica and ……. Mixes it thin, then flocculates it to a desired thickness. They all seem to work, are super cheap and easy to prepare and many find them reliable. Folks have “speculated” that Lees is zircon based. I am not sure anyone knows it’s actual composition and while true it is very hardy, it’s also hard to remove comparatively in my experience with it. Since much of clay is geologic (Extremely old materials) old knowledge probably is still pertinent and effective. Specialized refractory coatings have however improved over the last decade or two though.

Suggest: single fire with a bisque type speed schedule

To my knowledge it’s been unique and lots of folks always wanted it. My last visit to Axner, (a couple years ago) the manager said the recipe was under lock and key.

First natural gas has half the energy of propane so the orifices will be waaaaaay tooooooo laaaaaarge using propane. The normal method to convert is to achieve the same btu per burner with propane as you had with gas. So, gas typically is designed to operate 0-8” (not psi) and propane usually is sized 0-11” (again not psi). Easiest way is to look in an orifice table and reasonably match btu at the max operating pressure. This does require a second regulator for your propane though, (psi to inches) but really improves adjustability a whole bunch.

Lees kiln wash is like iron, won’t flake and is fairly expensive but it does work well. Can be purchased many places, here is one https://www.axner.com/kiln-wash-lees-by-axner.aspx Sue Mcleod has a nice recipe that is simple to make https://suemcleodceramics.com/how-to-make-a-good-kiln-wash-to-protect-your-kiln-shelves/ There are others here as well, maybe search kiln wash on the forum. Flaky is a big complaint, Lees will not flake and the various good recipes you will find generally the feature folks like, not too flaky, can be touched up relatively easily and can be removed with reasonable pressure / scraping.

As you can tell from the video it needs to be applied fairly wet whether by brush or applicator. Here is an article which also happens to have a recipe which contains clay to keep things suspended for you as well. CMC for brushing is common and extends the drying time. https://ceramicartsnetwork.org/daily/article/How-to-Decorate-Pottery-Using-the-Cuerda-Seca-Technique

A couple thoughts It would be fairly easy to test if wetting the body before your first glaze coat would solve this. It appears as the air is displaced from the pores of the bisque the glaze is too dry or not fluid enough to heal over. I have used premixed glazes in bottles as well that seemed to arrive in a variety of thicknesses. I would also test whether thinning this glaze to an ideal thickness will make a lot of this go away as well. As to whether it heals in the firing unfortunately is a trial thing as well, as some glazes do much better than others.

Just so there is no misunderstanding a PID loop is a logic function or combination of components that create it. Controllers use PID logic, fuzzy logic or other logic. The ras pi uses some form of logic to emulate the PID loop function. The Bartlett control is a full control that stores multiple programs, can be up to three zones, has a program interface (keyboard and display) , relay outputs, fail safe programming, alarm output, etc… It is a complete control with built in PiD(s) that are already tuned for the typical kiln firing process. Since it is multi-zone, it also contains the equivalent of three PID control loops. I mention because there seems to be confusion, as PID is a function, not a control and yes most temperature controllers contain PID logic and auto tune. It also seems you have all the necessary peripherals and parts to build a complete control. so for a couple hundred dollars, the Bartlett just might be suitable and an easy way to get multiple zones with weighted (helping) function vs three independent cheap temperature controllers. In a pinch, any temperature controller capable of being programmed through a computer interface / keyboard could give you an equivalent way to store multiple schedules and easily load as needed through a computer interface. Just mentioning, you might have everything you need whichever way you go. I still suggest you write out the design and anticipated sequence of operation.

Tuning properly can be extremely difficult. Auto tune helps a bunch but good PID loop process folks spend a lifetime becoming good at it. If it’s several hundred dollars it is a control with faceplate, circuit board, built in relays, built in PID, etc…. If you intend to use SSR or mechanical relays you would use the output of the V6cf to drive them. You will need a box, transformer, fuse holder, cord, wiring, SSR’s heat sinks etc… regardless of which controller, even a Ras pi will require all the support stuff and probably more actually A stand alone control will still need something to turn on and off which means relays, SSR’s box to hold them etc…. I am just saying, plan this out start to finish and I think you will have a better idea of how it all will work within your design. Right now there seems to be some confusion. The Bartlett has a PID already tuned for the typical thermodynamics of a kiln and places to store programs. The RAs pi is all your tuning -100% and you need to write the entire program as well. Economical temp controllers have a PID and auto tune, else you are going to have to tune and they still require all the support: box, interconnect wire, relays, etc….. I think if you define this completely an easiest path will become obvious.

The Bartlett controls - touch screen and old V6cf are PID based, likely without the derivative portion and are reasonably priced as well as capable of storing multiple programs including many pre maid for glass. I think the price range for the controller board is 200.00 - 400.00 so maybe something to consider. Most temperature controllers are PID based and provide lots of segments for programming and can be had in the 50.00 - 150.00 dollar range. Problem is programming is a bit of reading and learning thing. Most folks do not know how to tune a PID process, yet auto tune is available on most.

Must be a cone ten kiln I assume. 200 firings (cone 6) would be a bunch if you can make it. How many watts for the size and how well insulated it is are the main variables that limit most kilns.

If it’s truly a cone 6 max kiln it really will not reach cone 6 unless the elements are fairly new and all connections are spot on in very good order. At 6000 watts ( if this is yours).it is more suitable as a lowfire kiln. Cone 10 rated kilns usually provide 100-150 firings when used for cone 6 work because kilns are designed with only about 110% capacity new. If the elements have worn by about 10% they generally struggle to reach top temperature. If your element resistance has risen by that much compared to brand new then likely they are just worn too much. So easy enough to measure and determine if this is the issue. Most folks recommend cone 6 kilns be used for lowfire work only for this reason.

Just a comment here, crawling can often be the result of the fired glaze surface tension preventing its ability to heal so cracks developed early on can exacerbate the issue. Calcining part of the epk often can help with the shrinkage and help with the early formation of cracks. Interestingly ball clay is know to shrink more, but does not necessarily translate to more early formed cracks maybe because it is more plastic or has a more favorable fired glaze surface tension or both so you might have an idea worth testing.

Tried searching also, no luck. This may help in the interim https://suemcleodceramics.com/how-to-calibrate-your-kiln-sitter-for-accurate-firings/ Sue McCleod also has a you tube video. May help.

Sure DM me - envelop at the top of the screen

Re bisque them Cheap is fine, use a regular high temp kiln thermocouple though. I would also suggest measuring your elements and recording where they are from a wear standpoint.

My opinion, timer to go through and make sure your elements are all good, or they have not worn more than 10% by measuring their resistance. After which if all good calibrate you’re sitter so you have something consistent to work with. Then re- bisque or just glaze firing is up to you based on the importance of the piece and whether you bisqued some test tiles in this run.

Thanks for posting them, Just a question: do they ALL exhibit issues or are one or two of the above worse than the others?