Bill Kielb

Well, just my opinion: Barium carbonate is not something I ever include in my glazes for food use. It has more boron than required to melt at cone 04 so appears to be excessive for 04 - maybe ok at cone 08. It.has very low amounts of silica and alumina and falls in an uncommon area of Stull. It’s R2O is 0.27:0.73 so not bad in that respect. Hard to know without firing and testing for sure but the barium carbonate and very low silica and alumina levels for me mean I would not use it for food service.

Yes but too much boron has its own issues. Earth geology basically melts at cone 10 so not really a need for boron there. My suggestion: do some tests lowering the Si:Al or in your case sib:Al and observe how it becomes more matte as the ratio falls to 5:1 or less to better understand this ratio and the effect it has on a true matte. The Glazy link I posted above has Peters chart and a paper written by the guy who created that chart (Matt Katz, 2012). Also has some great references to other research that may prove interesting. You might want to open it and give a once over. https://wiki.glazy.org/t/understanding-the-stull-chart/857.html Here is a quick Katz intro video where you can learn a bit more about Stull. It contains the screenshot below which illustrates things fire by composition which means if you raise the amount of Alumina high enough it will require more heat to melt. Your glazes have been fairly high in Alumina so they ought to fire stiff by composition. https://youtu.be/-oRFAxpmaqE

Here is a interesting guess and why: everything with more than 0.45 boron will melt at 04 and with sib:Al of 7.0 will fire as some form of gloss. The relatively high alumina 0.56 ish will make these fairly stiff and maybe difficult to melt at 04 though so there is the possibility of an underfired matte. Just a guess though interesting to see how they all fire.

Just a thought …….. don’t be afraid of reducing your raw silica to get your si:Al ratio towards more matte. Often worth a simple line blend reducing silica to see the effect. Glazy has a free calculator that you could sub materials out, rather than guessing types and quantities.

RT Stull - a long time ago (Ray Thomas Stull, 1875-1944) understanding the Stull chart: https://wiki.glazy.org/t/understanding-the-stull-chart/857.html BTW if you put your glaze in a calculator, you will know some of those numbers which can give you an expectation of the melt.

I think I would add my 240 vac telltale to terminals one and two, non element side. Add a green 12vdc to the SSR control voltage and maybe even an amber 12vdc to the control voltage of the safety relay. I can watch everything operate so to speak. My guess (Hope) is that your meter is a bit out of calibration at the lower voltages. If this was more like 14 volts dc we likely wouldn’t really be having this conversation.

Maybe old school …. Get a 240 vac miniature pilot indicator, hook it to the output of the SSR and L2 neatly and visible. Get a cheap 12vdc miniature pilot lamp and hook it to the control voltage. They both should light and extinguish unless the SSR is stuck on. Neatly done, should be visible through the ventilation slots, different colors so you can tell which is which. Old school, telltale! Keep neat and away from kiln heat. Remove when finished testing.

The transformer is a pretty passive device with a fixed ratio of windings. More likely the input voltage is high, so then why? That goes to does it measure the same as the mains voltage, does the home have an open neutral, etc….. from there if still really high a call to the utility company as you should be limited to 240 vac +/- 10% I believe. Grounding is something I would confirm for sure as it will be used to mitigate any noise on the thermocouple input. Use of an unbonded neutral for the ground can cause noise issues. It needs to be a good earth ground. Since this can still point to thermocouple input issues I would double check that the thermocouple does not contact the metal case. I have seen them inserted a bit off center and when the kiln heated the side of the thermocouple would just touch the metal of the kiln creating all sorts of random noise.

Seems high to me especially if from a regulated circuit but your SSR functions 3-32 volts so not likely to make the SSR stick on. Since the symptoms have varied since the start of this with lots of Odd measurements I would confirm exactly what it is doing first. Is it overheating beyond the traveling set point for sure? Then work from ther as to why.

Since you tested the SSR and fixed the safety relay, I think the rate programming as @neilestrick mentioned is a great thing to check. This error seems to be one for overheating though so possible as the SSR operates and heats up, it gets stuck on. Which would be hard to diagnose unless you were there testing when it happened.

some very general rules that may help In general 7:1 SI:AL is highest gloss under old Stull so mixing glazes let’s say from 3:1 to 5:1 often gets you some form of true matte, which is always a matte even over fired it is a runny matte. As this ratio approaches 7:1 and beyond it generally becomes glossy so: +5:1 to 12:1 generally gloss glazes and highest gloss in and around 7:1. The benefit of knowing the expected texture it often points out when expected to be a gloss but fires matte, something is likely wrong as ……. it’s simply under-fired. For true mattes, simply adding more silica will take them toward gloss. Flux ratio R20 of 0.3:0.7 oftentimes thought of as ideal for durability and probably as low as 0.2:0.8 still decent indicator of durability. Much higher than 0.3:0.7 or lower than 0.2:0.8 often can indicate likely non durable chemistry. Boron (in general) 0.45 gets you a cone 04 melt, 0.15 gets you a cone 6 melt. This can be helpful if you are way under or way over, it's likely not ideal. Fairly simple boron requirements here: https://www.ceramicmaterialsworkshop.com/uploads/5/9/1/2/59124729/katz_tf_boroninglazes_0912.pdf

Specs are good! Funny the drawing shows off-center tap. I am guessing it’s just the drawing.

Makes sense, last I looked at the relays just under 2 watts each.

One thing to add a good glaze fit generally strengthens the ware. Crazed glazes can weaken it by providing a nice starting path for any defect to occur. Depending on the joinery, this shape is hard to build and keep the shrinkage rates reasonably the same. I am curious to the order of assembly making these and if any molds were used.

I think he is good 24v ct so 12 and 24VAC. His original picture is 5 va (5 watts) too small. 12 va (12 watts) sounds right

Small signal transformer, stamped 5 va? Looks too small, I would double check. 3 relays (~2W each) plus the electronics. I think worth double checking, picture is stamped 5va.

If you have not fired the glaze, then simply wash it off as long as the underglaze is fired on. If you have fired the glaze, I do not know of anything that will remove it without seriously harming anything underneath it.

Unfortunately if this is a fired finished product then I am not aware of any way to remove the glaze without destroying the piece. So I need to ask, has this been fired already?

Just a thing or two to think about: 30 gallons of water weighs about 250 pounds. The pressure on the cylinder walls will be dependent on the height of the liquid. (0.433 - about 1/2 psi for each foot). And of course the container itself will be the weight of the container plus the weight of the water so picking this up with two hands will place a lot of force where your hands are placed on the cylinder. Assuming 50-100 pounds of clay, this container full will likely be quite a challenge to pick up and move around.

I’ll give you my take. The vinegar test is very helpful and many glazes ought to pass it. Does it indicate durability, not necessarily so. It’s a nice test that can be done at home and any commercial ware ought to easily pass it IMO. Will it predict some of the complaint issues mentioned earlier which could go to glaze durability, glaze fit? Most likely not. Will it always predict leaching? Really not necessarily so, that is more of a lab thing. It’s definitely a good test to pass though. When a glaze does not pass it, for sure it is usually judged not a good glaze for food consumption.

First I would really suggest you figure out how many watts this thing has. The old 1700 degree nameplate sort off indicates it really ought not to go to cone 5/6. Next, you will need all that wattage to get there so if you remove 1/3 of your power it most likely for sure won’t make it. Last, for someone skilled in kiln service it would likely be possible to invert this kiln and have elements in the bottom so gravity aids in retaining the elements. This also requires a little knowledge in zoning and how kilns fire evenly. The top and bottom generally being the coolest with the greatest losses. I would first figure out how many watts this thing has which will give you an indication of whether this can be used to cone 5/6 for any reasonable length of time. More importantly it may reveal any wiring and control deficiencies you presently have as a result of someone prior having changed the elements but not updating the data plate.

I think the observations above ( @neilestrick and @Pres ) are very pertinent. Since you are learning glaze chemistry I will mention it’s really hard to analyze the mix chemistry but I have never really found a well working well melted combination non durable. Most folks just layer all combinations so lots of testing indeed is often the norm. As others have said contrasts have been the best for me often true matte and gloss. I actually only feel good about designing one fluid glaze I made fluid with additional boron to overlay or be overlayed. So fluidity would be one of my only somewhat predictable rules of thumb, confirmed by testing of course. In the pictures below The test tile is actually the glaze designed to run but fire semi matte and the titanium usually crystallizes as a fluid matte so variations of violet and blue emerge from what often fires as a predominately cream colored glaze. Rim dipped blue over the base sort of produced the desired “designed” result. Interestingly, the designed glaze turned very golden and began to dry up when fired only one cone higher. Highly likely not the most durable composition also, so only intended for decoration. Lots of testing, funny, even though it acted as designed, I never really liked the combo in the end. So lots of trial to me is really key. To add I think the test tile was the eighth rendition of substituting titanium dioxide and a touch of iron for rutile to try and get some consistency with the base glaze and not have to rely on a particular batch of rutile. Test tile #8 looks like not enough iron for the intended color. This probably took several more tests to get closer. Test, test, test!

And of course drying at home, but never in any rush with a temp hold there for sure.

Another option would be Euclids, they can wind for most. https://euclids.com/pages/kiln-elements

Yes, I did not mean to make that sound negative, apology and it does seem very interesting so thanks for sharing. As you say, it definitely must save time so I would be curious how much? Again, I am just old and chicken, never gonna take someone’s full bust sculpture and not be ultra conservative - just me though. fyi I am not associated with any particular studio as well, I have unlimited access to several that I have helped over the years but they are hours of travel away.