PeterH

If the slip is pourable when you come to emptying the mould then an airlock is a possibility. As is narrowing of the opening if the walls are too thick. However if the glaze is gelling it's a different problem -- think thixotropic house paint which sets on standing. The long-term answer is to adjust the slip until it doesn't gel during the time you are casting. Stirring the slip well just before casting (without introducing bubbles) can also give you a little extra time. While Jeff's stirring approach can break the gel in the mould. Long ago I was using a mould with a long thinnish neck very next like this, and an unsatisfactory ready-mixed slip: Pushing the handle of an artists paintbrush down the centre of neck and pushing it up and down for a while (while avoiding the sides) broke the gel in the neck for long enough for the mould to be emptied.

Congratulations. Fingers crossed. Presumably you improved some connections and/or the last switch you examined? But there are two pretty independent sets of (switch + element-pair), and some thing(s) have affected both of them. Maybe where two wires shared the same switch terminal (presumably on the switch you have just re-connected)? PS Reminds me of my software days. Heisenbug https://en.wikipedia.org/wiki/Heisenbug In computer programming jargon, a heisenbug is a software bug that seems to disappear or alter its behavior when one attempts to study it.

Idle thoughts ... sometimes you can error-guess, sometimes you need more data What tests have you been doing, and are they on the powered or unpowered kiln? Do you have a multimeter? Lets assume that the wiring corresponds to the diagram, and the components work. With the kiln unplugged and the meter measuring resistance you should be able to test for continuity ("zero" resistance) between the L1,Ll2 or neutral at the plug and the ends of the elements. Repeat with the 4-way switches in each position. So with one switch off there are 12 measurements for each position of the active switch. (L1,L2, neutral)x(both ends of top element, both ends of bottom element) = 3x4 = 12 ... if, as looks likely, the "middle" ends of pairs of elements are physically connected (e.g. go into the same switch connector) this reduces to 3x3 = 9. Basically demonstrating the the connections shown in red are there, and no other connections exist from an element end to the plug's L1, L2 & neutral. If some connections aren't there, trace them from L1/L2/neutral through the wiring, and see where connectivity is lost. If spurious connections exist, think about it. PS Two wiring diagrams for the A88B at https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/A82WD.pdf One for push-on terminals and the other for screw-on terminals. It also has a legend converting the b&w line-type to wire colour. I'd be inclined to colour-in a copy.

Two answers in one. Digitalfire https://digitalfire.com/ is a mine of pottery information, for example Underglaze https://digitalfire.com/glossary/underglaze

It looks to me like the top element (in the diagram, not necessarily in the kiln) is only fed by one of the 120v lines (the upper one in the stylised plug/socket). Although you say that both 120v lines are getting to the controller, is the upper one also getting to the switches and/or elements? PS >I have peered closely at that wiring diagram and wished for higher resolution a lot the past few days For a different kiln, but probably/possibly the same circuit https://content.invisioncic.com/r278179/monthly_2021_11/AFFD763E-B04E-4A36-A21B-049717307DB1.jpeg.d8d19f63656d62487cfde60f695535d2.jpeg ... asking for coloured felt-tips on the different styles of dashed lines

Something to keep at the back of your mind. IF the 4-way switches need replacing OR you don't have a 4-wire 240v circuit (L1,L2, Neutral, Ground wires) ... you can change to using infinite switches ( which also gives you finer temperature control) As (in some cases) recommended by the experts, and apparently Paragon (who seem to no longer stock 4-way switches). ... and Paragon don't seem to sell replacement 4-way switches anymore https://paragonweb.com/product-category/parts/switches/ ... remembering that a generic infinite switch from a high-volume supplier may be cheaper than one from Paragon.

I'd a faint memory of somebody trying this ... got it. Tutorial: Making paper plaster mould http://andrea-ceramics.blogspot.com/2015/05/tutorial-making-paper-plaster-mould.html I think I've also read of people just building up plaster layer by layer. PS With less plaster about it presumably will not be able to absorb as much water, so possibly slower casting and thick-walls/solid-casting an issue. It also must have less strength, so high-volume moulds are probably out. Although I think I've read of somebody supporting the thin plaster shell in a bucket of sand.

Maybe reconnect one switch and disconnect its outputs -- and then see what happens when you turn the switch on?

I've no experience in this area, but your problems might be to do with allowing time for crystal growth rather than reaching "maturity". Just a standard reference to slow cooling in an electric kiln, to emphasise sometimes changes in appearance are controlled more by the cooling cycle than by the peak temperature. Which may require down-firing in a kiln that cools too rapidly for that glaze/effect. Super Cool! Slow Cooling in an Electric Kiln https://ceramicartsnetwork.org/daily/article/Super-Cool-Slow-Cooling-in-an-Electric-Kiln

+1 After a little googling, this looks similar: https://www.thepostsupply.com/products/vase-no-8 I got largest image I could access from that page by opening this image into another window -- then clicking on it to enlarge it further. https://www.thepostsupply.com/cdn/shop/files/AnemoneVaseno.8_Red_1024x1024@2x.jpg Similar treatment for this one. https://www.thepostsupply.com/cdn/shop/files/AnemoneVaseno.8_main_1024x1024@2x.jpg

I assume that you are making moulds for slip casting (this limits the choice of release agents). Any idea what your masters will be made of? Are you intending to make drop-out or multi-part moulds? A picture of your master would give an idea if you are going to have to worry about undercuts. PS Somebody will probably move your post, as it will get a better audience in Mold Making and Slip Casting

Drifting off topic ... I'm starting to get confused, because there are two ways of measuring the density of powders. Bulk density is the weight of the powder divided by the volume it occupies (that's both the volume of the particles and any entrapped air). Obviously this can be influenced how the powder is handled before the measurement. Particle density is the weight of the powder divided by the volume of the particles. This volume can be measured by adding the powder to a liquid and observing change of volume. [The liquid must obviously wet the powder well.] I'd always sort of assumed that heavy & light ZnO differed in bulk density rather than particle density. Can anyone clarify things? BTW references to light and heavy ZnO seem thin on the ground. But this supplier seems to be offering 98% pure heavy ZnO. Which suggests that "heavy" doesn't relate to density variations due to contamination with other elements (but may relate to the production process used.) The listed "density" for this "heavy" ZnO is 5.606, wiki gives 5.6 for ZnO. https://ie.vwr.com/store/product/787678/zinc-oxide-heavy-98 PS An earlier glazenerd posting describing the two processes in more detail.

How do you support your slab when you move it?

How an Infinite Switch Works https://techcircuit.org/how-an-infinite-switch-works/ Surprisingly minimal inside the box. how stove infinite switch works. Internals/inside of it

The red box seems to have 20ER2 on it This infinite switch advert says Will also replace a 20ER1 and 20ER2. https://tdspares.co.uk/product/original-diamond-h-energy-regulator-simmerstat-burco-swan-water-boiler-thermostat-cooker

From https://community.ceramicartsdaily.org/topic/1557-gold-lustre-and-alkaline-glaze/?do=findComment&comment=10521 1. Lustre is a thin film of metal deposited on the surface of a fired glaze. It is NOT a glaze in itself. It relies on the glaze interaction with the lustre for adherence and this can be anywhere between 720.C-820.C depending on the hardness of the glaze. Earthenware glazes are usually refired between 720-750.C while stoneware and porcelain usually refire between 780-820.C but that is not set in stone. Every glaze is different and you would have to test to find the common denominator for your glazes. Glass, depending on the type, starts to accept lustre from 600.c onwards. You will know if you haven't fired high enough as the lustre will rub off. If fired too high it will start to burn off and be patchy. Commercial porcelain blanks can be tricky to find the optimum temperature as a lot of these follow the procedure of high fired bisque with a low fired glaze. This appears to be the same with bone china. It takes on the characteristics of the glaze it is on. If the the glaze is very glossy then the metallic layer is very glossy. If the glaze is matt then the metal layer is matt and this then follows on for all the permutations in between. However I have noticed in my own work that copper glazes seem to be more problematic as my lustres always seem duller. This then brings me to the second point. PS These lustres (there are reduction lustres as well) are based on resinates, which are metallic soaps. When they are heated they decompose to metal atoms and various gases such as CO2. Why most of them (e.g. copper) don't decompose to the oxide is complex, and apparently relates to the electron distribution within the resinate ion during its decomposition. Which is why resinates are still used. Danger of skin contact & fumes until they are fully fired, then you've got a metallic thin film (somewhat amalgamated with the surface of the underlying glaze). Some of the dangers are inherent to the resinate, others relate to the solvents used. Johanna DeMaine Lustre Ceramics Monthly Health & Safety and Overglaze Background Overglaze: Challenging the Myths

If your professor has a web page there may be some more handouts on it.

This might give you a better idea of some of the issues involved in getting the deflocculation right. Determining Dispersant Additions for Casting Slips https://static1.squarespace.com/static/527ac372e4b0d4e47bb0e554/t/527fd7f1e4b0c046bfa9b90d/1384110065234/Dispersant+Addition+Procedures.pdf

I wonder what is the relative contributions of the resistance of the wires and that of the various connections (crimped? push-fit? compression? soldered?).

KilnSitter models P & K manual http://www.fireright.com/docs/kilnsitter/pandk.pdf

+1 PS If you find the connectivity better with a phone it might be worth looking at phone lens adapters to give you a slightly longer focal length. Maybe a photographer here can recommend the best camera-subject distance and focal length for these demos.

From https://www.cressmfg.com/resources/ ... the best I could find is Basic Kiln Manual, for A,B,C Kilns (366kb) Kiln diagram C11HT Can you post a picture of your kiln sitter, or tell us what make† & model it is? For example, two popular kiln sitters are described in KilnSitter Operating Manual - Models P and K Lots of hits if you google Dawson kiln sitter parts ... purely as an example (as it has a nice picture) https://www.cromartiehobbycraft.co.uk/Catalogue/Ceramic-Kilns-Electric-Kilns-Pottery-Kilns/Kiln-Spares-Kiln-Elements/Dawson-Kiln-Sitter-Spares ... while Skutt has a more comprehensive list of KilnSitter® parts https://skutt.com/images/KilnSitter-Parts-List.pdf † And this is a trademark

Same here. I think its designed like that so that you can enter both @Pyewackette and @Pyewackette ... otherwise a lot of strings starting with @ could not be entered.

I thought that these were quite neat

Video of the polisher in action Possibly examples of the OP's work at: https://toaf.ca/gallery/jason-schiedel