Bill Kielb

interesting in the end Stull seems to have reasonably simplified all this to regions in his map and a matte / gloss line based on si:Al

Hmm, tell me that the new contactor is set up so power comes into the contacts marked L1,L2,L3 and the ELEMENTS are fed from the terminals T1,T2, T3.

There are several relays, including two solid state timers. You will need to locate where the hum is coming from. Does this kiln have a three position low, manual, high rocker switch?

If it is an intermittent high limit, you can jump the yellow and red for a supervised firing test. The thermocouple to that thing appears to be pretty small gauge as if it is only for use by that safety. ….. if it is a safety. Can you see where that thermocouple terminates? What temperature is it sensing?

I would submit, it’s powered (brown and blue) it has its own relay (nc, com, no), it has a pilot light that stays on and it’s thermally dependent but not adjustable. My total guess because of the non adjustable part, a fixed high limit.

Is that the controller or perhaps a high limit? Just curious what is on the front of that. It is powered and has its own internal relay.

Good catch! I thought his looked like 8 in the picture. Unfortunately 14 gauge has a lower lifespan, but if that is what fits. I have bent #8’s - no issue, just need a decent tool. I want to say the only #14’s I have found in a kiln was in someone’s alpine inside the protection tubes, twisted tip as well. Not good for longevity! Might have been a Geil that was reworked. For cone ten I would definitely try and use 8 gauge and if a complicated bend is needed a propane torch and decent needle nose pliers certainly make it easy to shape the 8 gauge wire neatly any way you might need. Looks like a standard protection tube with a spacer installed- just rechecking the picture.

I’ll be darned, nice relay! I see it’s rotary so one can always check if it is cycling by watching the rotation of the shaft. It can also be cycled manually from above with the right hex socket or needle nose players. The contacts look great, we don’t know what the drive coil looks like though. If this is a pilot relay it operates the large relay. One other thing to consider is your control likely has its own onboard relay that would drive this. Any and all those relays if intermittent likely would be affected by heat. If this is truly the pilot that drives the large relay, manually setting this to on briefly after the kiln stops cycling will narrow down the culprit a bit.

Hmm, my best guess here. It looks like element loads are split among the three contacts so prox 8.6 amps each. Depending on the rating which seems based on switching and derated at ambient operating temperature (60c), these contacts might be rated only at 9amps (switching prox. 300-600 times per hour) So the simple question would be if these contacts degrade rapidly, this relay is underrated and causing issues. The inrush from elements should be mild as compared with an ordinary tungsten lamp which is often briefly in excess of 8X, so this could work even at 60c - which is not that hot but seems underrated in and around kilns. It should be easy to inspect, if worn or burned with little use, you need a better rated relay, without the auxiliary contacts. Not sure why they are here anyway. If the other relay in the picture is the pilot for this, it could be damaged and likely will suffer a significant inrush to fire this relay. So simple to check relay contacts and understand what has failed or which contacts have burned excessively and replace as necessary. These are enclosed so not necessarily free air. 60c is not hot for kiln service, my thought is this is likely under rated. The pilot relay however will experience a reasonable amount of wear as well, even though only switching this contactor. It won’t last forever. Definitely check both for contact wear, obvious material transfer etc…. You should measure virtually zero resistance across any of the relay contacts when closed or if live definitely less than a 0.1 volt across them. Live stuff is live though and carries the danger of electrocution. Maybe a local kiln tech?

IMO, switching the neutral provides for the possibility of a higher resistance connection, something beyond zero volts. Most things are surrounded or in proximity to a ground plane of sorts so switching to me adds more risk. The specs are confusing to me, but why he has a three pole relay with an end switch is a bit of a mystery. If he has more than one set of elements, then that relay may be applicable. My assumption is those contacts don’t exceed 25 amps total load though. A few pictures of the wiring to the relay with context included for the connections would likely solve the mystery.

Yep, Stull! He was limited by available fluxes and his claybody at cone 11. The most useful for me is his matte / gloss line and with some indication of how it ought to fire which then prompts further diagnosis such as is this fully melted, etc…. We get the question of how to make a matte glaze here every so often. Slow cooling, magnesium matte are the typical responses and they are fine, but moving something between matte and gloss generally follows Stulls trend which is fairly easy. I have designed visually as well and Stull folks often group. I do like the simple true matte definition though and have observed the over fired runny matte as well as added silica from matte to full gloss. Sue M has some nice in studio testing and research detailing how to get better clarity etc…. Derek Au (Glazy) I believe is trying to gather data for a heat map to apply to the Stull chart. I am partial to Flux ratio as being an initial indicator if a glaze likely can be durable. The Katz research on boron required I find very useful as well. Cullen W Parmelee also interesting work - (Stull Era), lots more for sure not to be forgotten.

Looks like this is rated at 25 amps max and your load is 26 amps and each is rated at 9 amps @ 240 v.. This is also a three phase contactor with an end switch. You service should be single phase 240v, 1 hot wire and one neutral. Not sure this is the right relay for several reasons. Even though resistive circuits start without tremendous inrush, they do generate a lot of heating in the circuit though. It’s regular practice in North America to supply them with wiring and switching that is rated 125% though to minimize the effect of the heating on the switching device such as a circuit breaker. As a control relay, these contacts should be rated well beyond the maximum load for longevity. Since you have single phase 240v (not split phase like in North America) you really only need to switch the hot phase. Picture of how the elements hook to this would help, and the auxiliary contact is rated much less so depending how it’s used, could be an issue as well.

Yes lots of generalities around clay often don’t always hold up in all cases but being extra careful not a bad thing I suppose. Stull drew his map and did his research prox.. 1912 so maybe he indirectly inspired Currie. RT Stull was the head of the ceramics engineering department at the University of Illinois - my home state.

Nice picture(s). 8 gauge type K I believe. If you buy it 6” long then trim leads from the back to match the existing size. The good news is that the weld at the tip appears to be failing which definitely could cause erratic operation. Usually it corrodes away and is very visible see below. Yours looks like the weld is defective. To make a thermocouple the two dissimilar wires need to be reliably connected to each other. Your weld looks cold and twisted so may be intermittent. Still check all connections visibly and with a screw driver - the yellow thermocouple wire. Make sure the bare wire is actually under the screw and it is reasonably tightened FYI - After many firings, when we see the wear bellow we just replace them beforehand knowing they only have a few firings left on them. Picture of a new thermocouple below for reference

You may find this a good watch. https://youtu.be/DptgFBkynHA Sue is one of my favorites and recreated Stull and presented at 2018 NCECA. Her presentation was to simulate Stull in test tile form. To answer your question Si:Al ratio of 4.34:1 ends up to be relative as that glaze needed additional boron to ensure it would melt over heavy underglaze applications which was the specific issue we were trying to solve the summer of 2017. The additional boron does affect the surface. However, that glaze was designed as a true matte, meaning even over-fired it will be a runny matte. Anyway, no method is foolproof but if you use Stull as a reasonable guide to the expected surface it can become a game changer. Predictable surfaces often lead one to inquire and test whether things are under fired for the composition. Anyway, Stull kept his fluxes at 0.3:0.7 for good reason at the time, and fired and mapped the result. Sue emulated that in tiles as Stull becomes another tool in analyzing glazes. Sue does a great job of explaining it IMO and is worth the watch and read. Additionally there have been studies on mattes and durability and there certainly are many true mattes that are durable, so testing IMO is always wise. Funny, everyone wants to slow cool to get the matte look but a matte that develops later is ok and durable? I am not sure why that would be better but believe testing is always wise. Anyway, Stull can be helpful in my view and SI:Al has a pronounced effect on the final expected surface texture. Like anything though, just another tool, have not found the one stop analysis tool, limit formula, experience, etc…. Yet. It is interesting you sort of re-created Stull on your own. Sue has a wonderful site IMO and generally shares her research. Worth the read in my opinion. Her site: https://suemcleodceramics.com/understanding-cone-6-nceca-presentation-2018/

Type K are typical, post a picture of your thermocouple and the information on your equipment tag of the kiln. (Model, voltage, cone, etc…) to be sure. Thermocouples act like a battery and output a very tiny voltage proportional to their temperature so while it does happen, jumping from one reading to another may indicate a loose connection, contact with the metal shell of the kiln as things expand, etc…. The more pictures here (off the thermocouple and connections) the more informed the answers will be.

As you have experienced, there is a wide definition of matte surfaces often qualified as satin or semi matte etc…. Transparency varies as well, so some level of right up until it’s translucent. I think all perspectives are valid though. I have bowls matte on the outside for their aesthetic appeal. Some have gloss liners, some have satin finishes inside. The ones with zircopax often metal mark regardless of the finish. I think testing is the only way to find out if it’s appealing and acceptable and functional to you. I think my point about the recipe is it most likely can be done to fulfill your needs. The recipe I posted is simply one we created when we had similar needs. The real reason for my post is the glaze listed above appears to be is a lowfire or cone 05/04 style glaze. Since you are firing cone 6 it presents a bit of a problem or extra step to getting your clay fully vitrified and in the end may not fit.

It is true about the lids, for a few months for various odd reasons I lost lids to the pots I made. The rest of the topless accounting was a light hearted joke created by members in the studio surmising what could be done with the bottoms. It grew into the topless pottery marketing approach. Just a little fun.

Babs is spot on, post some pictures. Patch A Tatch is a fired solution. Your best solution could likely be an epoxy product protected from UV rays.

This should get you close. Less silica = dryer look, more silica it will go to a full gloss. No guarantees it fits your clay but fits our porcelain, Bmix and some others. And yes it’s relatively transparent. https://glazy.org/recipes/19734 Quite obviously you cannot reduce silica forever nor increase it. Our experience per the recipe posted it’s fairly dry per the existing recipe, fairly transparent and a sample has been in the dishwasher for years now without any signs of degradation. Some folks have posted very positive results on Glazy as well. I may as well add, for interior glaze you can add silica till more satin and generally eliminate metal marking etc… we had folks do this regularly so they could clear glaze the entire pot and maintain the look. I have a progression of it somewhere from very matte to gloss. If I can still find it I will post here. Ok found some of them, not the greatest but they go from a fairly dry matte to a full gloss. If you follow Stull at all, this is a fairly easy thing to work through. Sorry about the order and the Glazy picture is probably truest for the base glaze. Actually the sugar bowl below is probably the best close up example of the recipe posted on Glazy. It’s fair to add I am compelled to add any of the pots or references I post are for educational purposes and often are solely produced by me or in collaboration with my Marcia. The collaborative works can only be attributed to Madison pottery a single entity, but in many collaborations I am the thrower / glazer, Marcia loves the artwork and is truly a gifted artist. We do not sell any of the work, including any technical work I write about where the pottery community is the focus. Even though some of the work is my sole production, most often it is the result of a some form of collaboration over the years. The pot below was thrown by me, decorated by Marcia Grant and glazed using a glaze we worked on together under Madison Pottery. The glaze was subsequently published on Glazy for use in the public domain under Marcia’s Matte.

The samples above remind me of fashion art. Simple line work using pen or brush to capture the essence using gestures etc… If you google fashion artists you may find more samples and more inspiration. Folks who are good at it often capture things using pen and simple gestures very effectively with simplicity. Some fashion Artists here : https://www.fashionillustrationgallery.com/artists Andy Warhol definitely is in this list

How about painting / drawing it to your taste with underglaze.

@Roberta12 As they say, check anywhere lead can be so walls, blinds, surfaces kids can get their mouth on. For me it’s inside lid and sidewalls. 3m instant test instructions here https://multimedia.3m.com/mws/media/815979O/3mtm-leadchecktm-tri-fold-brochure-08-28-2012.pdf

Sorry to hear that, hope you do find some success and get a replacement or two.

Not sure what your elevation is but Northern California has had temperatures near or below freezing lately. It does look like the shelf is delaminating and might have experienced freeze thaw type damage. Just a possibility.