PeterH

Example of cobalt concentration vs depth of colour Cone 6 Ultramarine Cobalt Blue Glaze (Glossy Clear plus Cobalt Carbonate) https://www.thestudiomanager.com/posts/cone-6-ultramarine-cobalt-blue-glaze-glossy-clear-plus-cobalt-carbonate Tst ... but it doesn't have the cyan-ish tinge.

A picture showing the inside of one of the busts might help. Even better if there is something like a ruler in shot to give the scale. Either posted here or on your website.

Just another data point: electrical heating film for underfloor or sauna heating @ 440w/sq meter. https://tinyurl.com/2abs2xdf Didn't quite believe the difference in the wattage figures, so checked my maths. The rather large difference maybe related to the speed of response required?

Lots of good stuff by the experts over in the Equipment Use and Repair forum. Especially if you are considering a second-hand kiln.

Be aware that kilns advertised as cone 6 may have a short element life if regularly fired to cone 6. In https://community.ceramicartsdaily.org/topic/30261-paragon-dtc-800-kiln/?do=findComment&comment=228238 A cone 6 kiln firing to cone 6 will only get maybe 50 firings before the elements need to be replaced. Once they wear even a little bit, the kiln can no longer reach its max temp. In a cone 10 kiln firing to cone 6, the elements can wear a lot more before they need to be replaced. If your cone 6 kiln is getting more firings that that, then it is probably under-rated.

First a few caveats. 1) As you ask what is the diameter of the wire I assume that you haven't got it yet. If so, why use expensive nichrome when you are operating it at such a low temperature? Oxidation of the conductor isn't going to be an issue, so nichrome's big selling point doesn't apply. 2) At the temperature you mention the wire looses heat mainly through conduction and convection rather than radiation. These are very dependent on the (changing?) surroundings of the wire. 3) The amount of heat required to melt snow off the wall (I'm assuming the fabric is inside the wall) may significantly exceed that required when the outside conditions are dry. Do you have any guestimate of the weight of water that might need to be unfrozen? (It takes about 0.1 Kwh to melt 1Kg of ice once it's at 0C.) 4) While it still needs careful engineering, I suspect that a thermostat-based solution would handle the wide range of conditions better. Then a reference from the Electrical Engineering section of a Q&A site How do i find nichrome temperature https://electronics.stackexchange.com/questions/84516/how-do-i-find-nichrome-temperature ... I rather go with the second answer You can't. Sorry. The temperature of the wire depends not only on the electrical power on this wire, but also on the ambient conditions - i.e. how the heat is dissipated. This way, the temperature of the wire will not be constant in time, but will change depending on the air temperature and movement, materials that are in contact with the wire and so on. In order to make the temperature constant you will need to make the ambient conditions pretty stable, or to use temperature regulator that to regulate the electrical power on the wire in order to get the same temperature in different conditions. As long as the theory behind such phenomenons is too complex, the calculations are actually possible, but very complex. In most cases, experimental way is much more reliable and useful. Simply use regulated power supply and change the wire current until the temperature becomes what you need. But always remember that in other conditions it will be different. PS I see that StackExchange have tags that direct heating questions to interested readers. Maybe posting there would give you a better answer. https://diy.stackexchange.com/questions/tagged/heating https://diy.stackexchange.com/tags/heating/info I've almost no personal experience with StackExchange, other than it's software section which is always informative.

Interesting to know. Probably not an easily DIY-able process (unlike calcined alumina, kaolin, etc.) as seems to be melted & reground not simply pre-heated. Anhydrous Borax Alternate Names: Calcined Borax, Dehydrated Borax, Pyrobor https://digitalfire.com/material/anhydrous+borax Anhydrous borax is made by fusing hydrated borax into a glass and regrinding it.

https://lindabloomfield.co.uk/ ?

NASA seem to have had similar problems creating wind-tunnel models, there might be some interesting thoughts in: Improved ceramic slip casting technique https://ntrs.nasa.gov/citations/19940015904 ... and the associated patent Not least the idea of using a shell mould (i.e. constant wall thickness). PS They seem to apply (paint?) the shell on a wax positive. If you prefer to cast it then a previous reference might be relevant 3D Printing a Mold for a Slipcasting Mold https://www.instructables.com/3D-Printing-a-Mold-for-a-Mold/

I'm not convinced that the shrinkage of the clay against the undercuts will not harm the casting, but ... Recycling of plaster of Paris https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7276351/ Conclusions Plaster of Paris can be produced by thermal treatment of recycled gypsum powder at a temperature of 180°C for 2 h. The results of this project show that POP could be recycled repeatedly with the same procedure without altering the required setting time and working characteristics of recycled POP powder for prosthetics and orthotics, and even improving the compressive strength of casts. Thus, recycling POP could preserve the environment and reduce pollution. It seems that recycling POP could reduce the cost of importing new POP. However, further study is needed to compare the costs of importing versus recycling POP. ... remembering they were recycling dry plaster. ... and grinding it to a powder. In your case the firing cycle would have to be slow enough at the right temperatures to successfully candle the clay. Also you would need to dry out the plaster. PS Faint memory that maybe freshly made pieces can be candled faster/hotter than partly-dry ones. From https://community.ceramicartsdaily.org/topic/29727-candling-temperature-drying-greenware-in-kiln/?do=findComment&comment=227839 What I certainly don't understand is a point I heard Ian Gregory make. That he could fire (without candling) pots a few hours after he made them, but otherwise has to wait about a week to do so. A tentative guess is that a half-dry pot could have a dry (and thermally insulating) outer layer that lets the outer layer to become "too hot" before evaporative cooling kicks in, while a fully damp pot supports an evaporatively cooled interface moving gradually from the outer surface inwards.

I'm unsure that you can produce a plaster slip-casting mould with a lost-wax process. Wouldn't melting the wax contaminate the plaster surface? A highly speculative, but possibly relevant thread, relying on the thermal degradation of the plaster. @tkw954 Did you have any success? PS More details on the size and shape of your master would be helpful.

Rubbing indian ink (or black felt-tip pen) over a glaze, then wiping it off is a good way of revealing unnoticed cracks in your glaze. See from about 1:49 into this video

Related thread, especially

I would be wary of using a memento as a flower vase unless you are really sure that it will be fully waterproof. This requires a well-matched clay body, glaze and firing schedule.

+1 ... but my goto book source doesn't have anything cheap delivered to Malawi https://tinyurl.com/ff2mm2th

For a start just try UL Ferro frit in your search engine. For a start just try UK Ferro frit in your search engine.

If you are interested in glaze-over-glaze effects ... Basic "evening-class stuff", but a big test tile with a stripe of each of N glazes one way, overlain with a stripe of each glaze at right angles shows you the effects of all N glazes under/over all the others. I wouldn't try with N=60 though! ... a blank line in one direction [so an Nx(N-1) grid] shows single and double coverage of each glaze as well. The chief drawback is that you are only showing a spot of glaze fired on a smooth horizontal surface. Which probably isn't a big issue with tests for mosaic tiles. Still doesn't explore variations of glaze thickness (although the N+1 idea helps). PS Cannot find a picture at the moment, so I'll try to draw it. Underlined letters written on the test-tile. x/y indicates glaze x over glaze y. top A B C -- a b c A a/a a/b a/c B b/a b/b b/c C c/a c/b c/c ... here is an example with paints rather than glazes https://www.chrishilbig.com/review-golden-open-acrylic-paints/

A visual reminder that a little water expands into a lot of steam, rather quickly.

There is a user manual Page at https://device.report/manual/5720904 PDF at https://device.report/m/1c60d3e1d7c310b0b77655d1833e5aed8cbe06b41c530da1e376becee2620554_optim.pdf ... although it doesn't say much I expect that the RCD (residual current device) avoids the need for a user-replaceable fuse. (Although there might be a service-engineer-replaceable fuse hidden in the guts of the wheel somewhere.) Between them the two lights should indicate if power is reaching the wheel internals. I suspect that the stand-alone light indicates that power is reaching the box, and the light on the blue panel indicates if the RCD is letting it through. Can you say what lights you have on? from https://m.media-amazon.com/images/I/81Hi6FfkgqL._AC_SL1500_.jpg ... possibly from a different wheel.

This has been a learning experience. I've posted fresh ideas, new readers start there. PS Some of my previous posted ideas left here for completeness. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- A quick google failed to find a public domain manual. Although there was a site offering/purporting to have it, I'm always a bit suspicious of those. I assume that you've checked the fuse in the plug. It looks like it might have what we call an ELT (earth leakage trip) in the UK. from https://tinyurl.com/39sknyej Have you tried pressing what looks like a rectangular button on at the top RHS of the blue plate (while the power is off) it might reset the ELT. PS The "Leakage Protection Device" arrow seems to be pointing to a lamp, rather than the second button ELTs usually have. Can you confirm? ... found a better image (possibly from a different wheel) from https://m.media-amazon.com/images/I/81Hi6FfkgqL._AC_SL1500_.jpg Which looks like the rectangular button is a "test" button (trips the device). So how do you reset, is it just switching it on (which you are already doing)? So maybe I'm just saying make sure you switch it off then on again while the power is connected -and report what the lights do. PPS If you want to risk it (they might be clickbait) https://lb.manuals.plus/vevor/gcjx-series-pottery-wheel-machine-manual#axzz88NpegZVN https://device.report/manual/5720904 ... the second has some general advise on the page

From Neil's Links To Kiln Manuals, Wiring Diagrams, Repair Parts, Elements, Etc. The Paragon Kilns link leads to the circuit diagram for this part number https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/S0743-1.pdf The 1/2amp fuse guards the transformer and the 24v controller it supplies. > As it was ramping up, about 45 min. into the firing, the internal fuse blew and there was a slight electrical fire smell. > I replaced to switch and the fuse blew again immediately upon plugging it in and turning it on. Naively, if the fuse now always blows at switch-on, I would suggest to the shop that they: - check the connections to the transformer - fully unplug the controller - and see if the fuse still blows - if the fuse doesn't blow check the voltages at the transformer between ORN/BLU, ORN/WHT and BLU/WHT. I would expect one of them should be the board's 24VAC? power supply. ... should help differentiate between the transformer (and its wiring) or the controller (and its wiring) being a problem.. But wait until one of the experts here confirms this is safe/sensible to do. PS I'm confused by the inverted-U shape shown on the diagram . It looks like it might be a link/strap but the transformer seems to only have seven terminals. https://paragonweb.com/home/transformer-2/

What model is it, there are several Caldaras. There should be a plate on it somewhere showing voltage, amps, watts, etc. Look for something like: Can you post a photo?

A google for dutch molds turns up several hits, including Catalogue at https://www.dutchmolds.nl/ ... but seems to be in Dutch.

There is a John's Noxema 117/5 at https://www.flickr.com/photos/glazes/40006967621 ... is this the recipe you use for the bottom glaze? PS Glazy has a Noxema https://glazy.org/recipes/6522 and a Noxema Blue https://glazy.org/recipes/2475

> And beside that how can I calculate it so that the object would get out of the setter in one piece? Note that the bone-china reference I sent used a one-time internal setter. As this was made of the same body as the pot being fired their shrinkage should be similar at all stages in the process. Obviously this isn't true for kiln-furniture style setters. As I've said previously, my concern with an outside setter is managing to keep the slot-ridges undamaged. > This would achieved with a fully closed mold I take that to mean you will be using a 2-piece mould, with the each piece defining one face of the cone. This mould would presumably also fully define the slot and its associated ridges. (Concerns about de-moulding the thin ridges and "dropping-out" a form with a slot.) I've done almost no solid casting, and worry that the thinness of your walls might be an issue when filling the mould.