PeterH

Apologies to all, a real senior moment.

If you heat air from 0°C to 1000°C it expands to less than five times its size. [It goes from 273°K to 1273°K and expands to 1273/273 its size.] Water expands by about 1700 times when it turns into steam (over a much shorter temperature range). at's a lot.

You could prevent the mould by adding a biocide. Short lived ones (that require topping up) are hydrogen peroxide and bleach (but bleach may be hard on the hands). A long-lived one is copper carbonate. The Best Way to Eliminate Odor from a Stinky Ceramic Slop or Glaze Bucket - Try to make sure that your waste doesn't get near any aquatic life, especially if you use a long-lived biocide. - I could understand your "wild" clay going mouldy if it has lots of organics in it, but am surprised that shop-bought bentonite does.

Thinks for posting the kiln plate. I hope that the experts will chime in, but I suspect that the max temperature of 1300C means that the element life - when firing to your desired temperature -- is likely to be quite short. For example see the first answer in PS I'm not certain if the figure of 50 firings includes the lower-temperature bisque firings.

You may find this of interest, especially the sections What is Heatwork? and Put Witness Cones in Every Firing. Temperature vs Heatwork – Why We Use Witness Cones https://suemcleodceramics.com/do-you-put-witness-cones-in-every-firing/

I don't know the best place in the UK to get elements, but some of them will probably try to reproduce elements for kilns from defunct manufacturers. For example: Kiln Elements, Repair, Servicing and Support https://www.potterycrafts.co.uk/Products/kiln-elements-servicing Can you post the information from the plate here as well. PS The plate probably looks something like this, partially printed and partially stamped.

Both seem very sound advice (while the elements are worn). So does this mean waiting for appropriate safety glasses? Are we talking about welders glasses for IR & UV protection? In the Studio: Eye Health for Potters https://tinyurl.com/3tcnc8tp PS Or -- in the absence of goggles -- could you measure the rate of temperature rise towards the end and stop the kiln closer to the right heat-work. Although you only have figures for 15C/h, 60C/h & 150C/h. BTW -- assuming you have a controller -- what is the rate of your last ramp?

A cone temperature chart confirms that this is a real effect. A cone number relates to an amount of heat-work and the maximum temperature needed to achieve this depends on how fast the kiln is heating towards the end of the firing. https://www.overglazes.com/PDF/Orton-Cone-Chart-C.pdf Did you previously fire by observing the cone drop or just use it as record of the firing?

I haven't heard of this before, do you have a trade-name for them? This explains a/the mechanism, and may be a starting point for some DIY-er . How to Build an ON/OFF Switch for a Permanent Magnet https://interestingengineering.com/video/build-on-off-switch-for-permanent-magnet The ones I saw on the net looked expensive, and possibly overpowered for the application.

Possibly the right wiring diagram, but too blurred for me to read https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/W-EA-820-8-Control-Panel.pdHasf It looks like the lower elements are fed by a power relay, are we certain that it isn't suck? (It might still click.)

Lots of pix at https://tinyurl.com/2rkyb27z ... two particularly lo-tech ones are It would be interesting to know if "fingerdips" work Use a car dent puller to dip your pots in glaze! https://tinyurl.com/2p9y6bn3\\\\\\\\\\ Apparently suckers can be useful in some circumstances

And I understand that slow-cooling can add to the available effects from some glazes in electric kilns, by giving them more time to develop crystals. Super Cool! Slow Cooling in an Electric Kiln https://ceramicartsnetwork.org/daily/article/Super-Cool-Slow-Cooling-in-an-Electric-Kiln From https://digitalfire.com/picture/bestenazoh Firing for Atmospheric-like Effects in an Electric Kiln https://tinyurl.com/cf7ef94y Fuel-burning kilns tend to be much larger than electric kilns. Because of their size, they usually have a slower heat rise, a soak at the top temperature, and slower cooling cycles. If you want similar results from an electric kiln, especially when firing to cone 6, one of the most important things you can do is emulate the heating and the cooling cycles of larger kilns. This means slowing the temperature gain to about 100°F (38°F) an hour during the last several hours of the firing, soaking the kiln at the top temperature, and then down-firing to slow the cooling cycle. Electric kilns are built with thinner insulation and legs (to allow for air circulation), and they cool very quickly, especially at higher temperatures. If you are seeking buttery, matte surfaces but have trouble achieving them in the electric kiln, it is most likely due to fast cooling. Matte surfaces are usually caused by microcrystal growth during cooling, and, if the cooling cycle is too steep, there isn’t enough time for crystals to develop. In extreme cases, I’ve even seen matte glazes go glossy and transparent. ... note that the 100F(38C) above is "finger trouble", see What is the difference between fahrenheit degrees and degrees fahrenheit? https://digitalfire.com/picture/2704

Can you give a reference? It would be interesting to know why he chose to mix by hand rather than mechanically, sounds a bit hair-shirt to me. You may find parts of this video of interest, especially from about 24m to 31m. It describes the gradual realisation of the nature of the slip used in antiquity for things like Greek red-and-black and "Roman" Samian ware. Terra Sigillata: Lost & Found by Peter Pinnell & Rhonda Willers Long before glazes appeared, clay finishes were widely used. Potters around the Mediterranean developed surfaces employing the unique properties of clay. Once lost, Terra Sigillata was found after 1500 years. This co-lecture provides a history of this surface with an overview of today’s practices. ... of course this doesn't say how it was made. I suspect this is lost in history. I doubt deflocculation would leave identifiable traces, and it the process may well have been a trade/craft secret. Use of deflocculants such as soda/pearl ash would have been possible. I've even seen a suggestion that a good way to find a natural source is to wait a decade or so for a major drought and then explore the dried-up beds in the local lakes. Some of them will consist of ultra-fine particles (sort of a super ball-clay*). Personally I've wondered if waste-water from the production of clay for the bodies could have been a starting point, as it would probably have contained colloidal particles. * Supposedly the change of pH when river water enters a lake favours the precipitation of colloidal particles, potentially leading to a very fine silt. PS The video quotes the historic use of the term "magnetic" - obviously we would now say "electrostatic".

I think this is the right manual Duncan Energy-Saver ES & EA Instruction Manual LX851 https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/LX851_Duncan_Energy_Saver_Owner_Manual.pdf On p13 it says What is the relationship between your "clock-face" numbers and any labels on the on the kiln, such as ... and why doesn't this picture show anything that obviously corresponds to the "low" marking mentioned in the manual? Unless "off" in the picture is the equivalent of "low" in the manual? Which makes some operational sense (as you report that it does heat up the kiln) but no linguistic sense.

Still a very good question.

First a brief statement of the pros and cons from Understanding the Deflocculation Process in Slip Casting https://tinyurl.com/2p96x33r BTW https://digitalfire.com/ is a great site for background reading So, it's a bit more complicated than simply adding x% of a deflocculant. For a given clay/water mix you are basically trying to add defloculant to achieve a low viscosity, while keeping safely away from the over-deflocculation ... and hoping that the result doesn't gel unacceptably. A comprehensive process to do this from scratch is given in: Determining Dispersant Additions for Casting Slips https://tinyurl.com/34khjunr Even if you don't do things this way it gives a clearer picture of what you are trying to achieve. PS I understand that the modern polymer deflocculants (eg Darvan) give superior results, are easier/more-foolproof to use, and damage the moulds less. While many sodium silicate based slips also benefit from the addition of soda-ash/sodium-carbonate. [Warning: Darvan should be store above 10°C.]

Any relevance, or are there too many non-standard cables about? Thermocouple Cable Colour Chart https://www.pyrosales.com.au/blog/thermocouple-information/thermocouple-cable-colour-chart/ ...and https://www.hgsind.com/videos/how-identify-thermocouple-wire-color In this video we’ll be focusing on the ANSI wire color coding used by the United States and Canada.

... or type it in if you are having problems posting pictures.

Googled across this image transfer technique. It uses a laser-printed image to produce a one-time transfer "plate" needing to be inked up. How to Create an Underglaze Transfer using a Photocopy , Our Halloween Project https://www.baileypottery.com/blog/post/print-out-photocopy-transfer-in-halloween-style.html PS Sorry @oldlady's image transfer pics are gone. Some tiny snippets of Kim Kirchman’s work 30 second video of her painting an image https://www.youtube.com/watch?v=NVNuEJU5uQ8 A still of a different image being pulled, looking pretty crisp https://www.instagram.com/p/CRMUaH2DBQ8/ Low resolution video of an image transfer at 7:38ish in https://youtu.be/-txcJjLjQZ0?t=421

Can you post a close up of the plate?

This is a very informative site: Maturity https://digitalfire.com/glossary/maturity

BTW I quite like this colour combination, and the visual interaction with slightly blotchy background. ... its a manganese dendrite, typically formed by manganese rich water seeping into a crack in a limestone bed.

A low-tech way of achieving a deflocculated slip is find a bed of clay which deflocculates well when alkalies -- such as soda ash or wood ash -- are added. When this happens it can be because the clay contains tannins or lignite/lignates. Taking a more chemically informed and proactive route both tannins and alkali can be added directly, as in: Mechanisms for efficient clay dispersing effect with tannins and sodium hydroxide https://tinyurl.com/m5w2cyz8 Tannins appear to be fairly easily extracted from natural sources, and historically may already have been in use in the tanning industry. How to Extract Oak Tannins https://www.ehow.com/how_12001502_extract-oak-tannins.html A paper recommending the use of tannins for deflocculating drilling mud: Evaluation of a Naturally-derived Deflocculant (Terminalia Chebula) in Bentonite Dispersions https://tinyurl.com/5n6crm5r PS Also found this reference, but have not managed to access the text. The book is available for ~£35 ... I expect this relates to current practice, and is not inconsistent with the use of something more like water-slip than deflocculated slip.

Just maybe relevant: Slipcasting https://npceramics.wordpress.com/2017/09/06/slipcasting/ Historically, there’s seems to be some debate as to when slipcasting was actually ‘invented’. It is fairly widely documented as being a process that became established as a viable manufacturing method around 1745. This is when both deflocculated slips and plaster of Paris moulds were readily available. Prior to this ‘water slip’ had been used for casting, but it had a variety of disadvantages; the main on being the saturation of the moulds. This not only drastically shortened their working life, but it also took ages for the plaster to dry out between each casting. And any casts that were then successfully removed were prone to high rates of shrinkage and distortion, due to their high water content. Overall, this meant the failure rate from start to finish was uneconomically high. ... it then goes on to mention Peruvian panpipes My understanding is that the Dawson's paper you referenced is suggesting that the pipes were cast individually* and then joined by adding additional clay by hand. This sounds like a relatively undemanding requirement, so perhaps a relatively low-tech casting technology would be adequate. * Although the set of pipe moulds for a complete panpipe were held in a common structure. Chinese slipcasting is probably a different story, but so far I've only found statements that is was done and not found any description of the pots produced (let alone the process).

Robin Hopper confirms that the use of stains is OK in Mocha Diffusion https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/Mocha-Diffusion# A comparison of different "pigments" "acids" is given in An Exploration of the Variables Involved inCreating Mocha Diffusions https://francesgwilliamceramics.files.wordpress.com/2019/06/an-exploration-of-the-variables-involved-in-creating-mocha-diffusions-frances-gwilliam-st20086157.pdf ... on p21 it states that At stoneware temperature there is colour loss in the tendrils. The main body has the same metallic brown as it has at the unglazed earthenware stage, but is slightly shinier. When glazed the colour is almost completely absorbed. Even on the main body the colour vibrancy decreases significantly. The tendrils become very faint lines. Manganese Oxide works well initially as colourant for mocha diffusion, but I wouldn’t suggest using it above earthenware temperature with glaze. The colour stays mostly consistent through firing temperatures but is absorbed too much by the glaze at higher temperatures. PS Stumbled across these, which might be of interest A rather "different" style of feathering See https://www.youtube.com/watch?v=cSrWRWILaZo Thought provoking eye-candy Satisfying Mocha Diffusion Compilation https://www.youtube.com/watch?v=WjocYCaPsUM And a classroom science paper in Japanese (Google translate doesn't seem to work). Fractal growth method applicable in class: Fractal dimension and growth characteristics of Mocha diffusion patterns with surfactant https://tinyurl.com/mr3hfj6v The pattern when the dye solution containing polysorbate80, a surfactant, was dropped on a 1: 1 mass ratio of kaolin and water was analyzed. so it's definitely not a pottery experiment, but it does raise some interesting questions - would surfactants work instead of the usual "acids" (e.g. washing up liquid or dishwasher rinse aid) - as altering the concentration of the surfactant influences the "openness" of the pattern, would watering-down the concentration of the acid have a similar effect? Maybe 50:50?