PeterH

Perhaps a more eye-catching title title would be "Korean-speaking potter needs help".

Good idea Pres. May I suggest that @scottiebie considers trying to enlist the help of those Korean speakers on the forum. Perhaps by starting a new thread (with a title something like "Korean-language beginning-throwing videos and posters needed") explaining the problem. Maybe one of the more mainstream groups such as Studio Operations and Making Work would be more likely to catch their eye. A very superficial search suggests that English speakers might easily get overwhelmed by the number of Korean-language items on throwing Korean-style pottery (usually by experts).

I'm a great believer in "If it ain't broke, don't fix it". So I'm in total agreement that keeping to your tried and true process is the smart thing to do. To play devils-advocate. You are ensuring that there won't be problems during candling (by keeping below boiling point), and relying on your experience to know that any residual pore-water won't cause problems during the bisque. While somebody candling to 240F is ensuring that there won't be problems during the bisque (by removing virtually all the pore-water) , and relying on their experience to know that this won't cause problems during the candling. IMHO both are admirable strategies.

Most of it according to the first diagram I could find. Their ramp looks faster than yours, but I've no idea how "dry" the clay needs to be before starting this bisque firing. https://cawstudiopotters.wordpress.com/exp/kilns-firing/ Hamer & Hamer gives: The water of plasticity dries out from the clay in the atmosphere. The pore water is driven off by heat up to 120C (248F). The bound water remains as part of the clay compound (Al20O3,2SiO2,2H2O) until red heat, 600C (1112F). Elsewhere H&H say: the point at which the clay is theoretically bone dry is 120C (248F). I'm not sure what is meant by theoretically here. Is it the same thermodynamic style of argument that says diamond spontaneously decays into carbon (which it probably does, but it takes geological timescales to do so). I've no idea where (on the above diagram) all the water of plasticity has been expelled. Nor how much might be present before candling starts. PS Looking athttps://www.lakesidepottery.com/HTML Text/Tips/Clay drying and firing process.htm When the water has evaporated form between the clay particles, and all the remaining clay particles are in contact, drying shrinkage is complete. This is called the leather hard stage. The particles themselves are still damp, but their drying will not cause any additional shrinkage. So maybe the terminology is as simple as: Wet clay has water of plasticity, pore water & chemically combined water. Leather hard clay has only pore water & chemically combined water. Bone dry clay has only chemically combined water. Bisque clay has no water at all. ... which still leaves the practical matter of telling when an actual pot reaches these idealized states.

All embarrassingly good questions, I'll only answer the last one. Stuntman, singer and potter, he was somewhat of an exhibitionist and - at least at exhibitions - fired fast. His shopping-trolley kiln took about 10 mins for bisquit or raku, and 30 mins for stoneware. My vague memory was that his little-rocket reached cone 9 even faster. [Not certain if he used temperature or cones.]

In answer to your question. For water below it's local boiling point inward heat-flow causes the temperature of the water to increase, when the the local boiling point is reached some of it is converted to steam. The local boiling point is a function of the local pressure, which in turn will be influenced by any back-pressure generated as the steam tries to escape. AFAICT bara = absolute pressure in bars (atmospheric pressure is around 1 bar). My post was really just applauding @Kelly in AK for making the point that the thermocouple temperature doesn't indicate the current temperature of everything in the kiln, rather than offering a solution to the candling problem. And throwing in a little physics to indicate the complexity of the situation when evaporative cooling is involved. Hence just looking at the kiln's thermocouple probably doesn't give much insight into what is happening at the water-air interface within a damp clay body, and certainly not the temperature there. So - for example - wondering if the thermocouple can safely show a temperature just above boiling point (at atmospheric pressure) probably isn't a useful question. BTW I calculate that the 240F mentioned in the first post is the boiling point at ~2bar, so it cannot produce an back-pressure of more than about ~1bar. Hence 240F could well be safe for "normal" pots. ... figure generated via https://www.engineeringtoolbox.com/boiling-point-water-d_926.html?vA=2&units=B# ... I would certainly agree with treating "demanding/thick" and "high-invested-effort" items such as sculptures more conservatively. 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. Anyway Ian Gregory's comment suggest that all damp pots are not equal, so we probably have to allow for the likely worst case in the load. In which case for normal pots perhaps a temperature picked to be incapable of generating "high" back-pressure might be a starting point, and a time derived from experience. Which is pretty well where we started. PS Has anybody done IR temperature measurements on pots while they are candling?

This background reading explains how the various types of electric motor can run "backwards" if mis-wired or a replacement wasn't a "drop-in". How to Reverse Your Electric Motor https://www.hecoinc.com/blog/why-is-my-motor-running-in-the-wrong-direction

Yes indeed. While it takes 100 cal/gm to heat water from freezing point to boiling point it takes another 541 cal/gm to turn it into steam. In domestic terms you put an uncovered stew in the oven at 180C and it fairly rapidly reaches boiling point, but then quietly sits there evaporating for several hours at 100C. The downside of course is that water expands by a factor of 1600 when it turns to steam, which needs to escape. Don't know the figures for chemically combined water. Latent Heat and Freezing and Boiling Points https://www.e-education.psu.edu/earth111/node/841 PS Loosely related The Art, Science, and Allure of Spain’s Water-Cooling Jugs https://www.atlasobscura.com/articles/botijo-jug But behind its apparent simplicity, the details of the botijo’s cooling system are incredibly complex. In the 1990s, two Spanish scientists developed a mathematical model to explain the details. They placed botijos in an oven and measured the water evaporation rate and the temperature drop over time. In the end, they came up with two lengthy and complicated differential equations to explain the mechanism. An ancient method of cooling water explained by mass and heat transfer http://quim.iqi.etsii.upm.es/botijo.pdf ... they placed a botijo full of water at 27.5C in an oven at 39C (simulating a hot day), seven hours later the water was at 24C. ... and you certainly don't want to follow the maths, but I don't expect that for candling pots is any simpler.

I'm not an Instagram user, but this might be worth looking at https://www.instagram.com/explore/tags/glazesharing/

Joanna Oliver uses it see https://tinyurl.com/mr23nadx You might try asking her, contact link at top RHS of https://www.joannaoliverceramics.com/blank-mpvle She sounds like she might be willing to share recipes:

Could you share the picture with us?

Although never say never ... https://www.plumetismagazine.net/technique-poterie-tournage-corde/

I cannot remember where I first saw mention of this technique, but I suspect that it was in one of your postings a decade or so ago. This image part-way through the stop-motion video I linked confirms that the clay is not coiled. Also note the profile board defining the outer shape The clay looks (and is described) as rather softer in another reference https://deborahsilver.com/blog/tag/handmade-garden-pots/ It is much more efficient to press the sticky clay into the rope. The form keep the clay from succumbing to gravity. ... These pictures detail how the wet clay is pressed into the rope covered form. The texture you see here-the finger marks of the person making this pot. ... Once the wet clay is pressed into the ropes, the wheel turns, and the surface is smoothed.

While trying to re-find earlier references I came across this smaller-scale example: John Maude demonstrates 'Jarre a la Corde'. https://www.easybats.com/jarre-a-la-corde-fun-stuff.html The frame and central axle idea looks really promising for heavy/tall pots, and might also take pointy bottoms in its stride. ... John Maude might be a useful contact. A google for Jarre a la Corde throws up a lot of interesting hits, including videos. PS An earlier ref still seems to work. ... although sadly the reference http://www.terre-en-formes.com/en/savoir_faire.html no longer works. PPS An image search for Jarre a la Corde also turns up some interesting pictures, for example showing different frame constructions. The first to catch my eye was http://www.prometheas.fr/blog/rencontres/rencontre-avec-pierre-bruzzi-la-corde-sensible-du-potier.html

I assume that this graph shows the progress to 1080C (and the kiln just hangs from there, but this isn't shown) ... is it coincidental that this glitch happens at the end of one ramp and the start of another? If the kiln was simply running out of steam wouldn't the angle of the ramp gradually reduce -- unless there was a sudden change in the thermal situation (like the lid springing a little further open).

For what it's worth, a firing schedule by original 4-way switch positions and the resultant power to the elements.

Is the handle also cast, or are you joining dissimilar bodies? PS Should you contemplate changing your process you may find some relevant comments in this thread, which covers more than the title suggests.

My guess at the physics of the process... Sodium Silicate is not a release agent, it's a deflocculant. It lets you make a workable slip with less water. But it's not the more the better, there is a sweet spot (which your usual casting slip will/should-be close to). Basically the mold sucks water out of the slip causing it to cast. The casting get slower as - - the cast walls get thicker (more resistance to water flow) - the mold gets saturated with water (and stops sucking) The first required patience (and perhaps optimization of slip properties). The second requires -- - either a thick mold which can comfortably absorb all the water that needs to come out of the slip to complete the casting. - or exceptional patience to wait while water evaporates out of the saturated mold, which then can start sucking again. - in either case starting with a really dry mold can only help. That's because in that case the extra water may saturate the mold even when you are only casting thin walls.

MOP over a black glaze

But probably only if you have high-current sockets installed. First can you confirm what your actual supply voltage is. I suspect that you are like the UK in having a notional 230V supply but actually receive 240V. [Most of Europe has the same notional 230V supply, but actually receives 220V. This gives inter-operability for most electrical appliances, but doesn't work too well for heating devices & light bulbs. The full story is in https://www.se.com/uk/en/faqs/FA144717/#:~:text=The UK used 240VAC 50Hz,including UK and Irish Republic.] Assuming your supply is -- and will continue to be -- 240V the socket will need to safely supply the current drawn by the kiln. Obviously this is at least the 20A on the kiln's plate. In the USA it would legally need to be at least 25A (see PS), other locations may differ. [If the actual supply isn't 240V you may need to worry about element resistances.] So which of these socket types do you already have installed? https://en.wikipedia.org/wiki/AS/NZS_3112 PS PSS I cannot read all the details on the kiln plate, could you post a larger image? Does the kiln have a plug? If so which socket type does it fit? Again a photo might help.

A and B series instruction and service manual https://ltt.arizona.edu/sites/ltt.lab.arizona.edu/files/SM and MED Paragon A and B series Instruction and Service Manual.pdf A diagram showing which elements should receive how-much power for various settings of the rotary switches is shown on right -hand side of p24 (26th page in pdf) and the top left of p25 (27th page in pdf). For example ... Firing Schedule Poster https://paragonweb.com/wp-content/uploads/A-82B-FSP.pdf ... I've no idea what the "Extension Switch" is.

Hopefully somebody knows how to achieve the "shimmer" you want without spraying. Can I suggest that you don't take the airbrush idea any further until you have carefully assessed the H&S aspects. I have no practical experience with lustres, but did know years ago I did know somebody who had a garage industry making them. He was so un-enamoured with the solvents used in main-steam commercial lustres that he restricted himself to using turpentine. Expensive but safer to use. A couple of references to start the ball rolling. How to Use Ceramic Luster Glaze https://ceramicartsnetwork.org/daily/article/How-to-Use-Ceramic-Luster-Glaze Use a properly fitted respirator that blocks fumes during application (1), and work in a ventilated space with plenty of airflow. Ceramic luster glaze has toxic fumes when it’s in liquid form. As long as the weather is nice, I apply my luster outside. Lusters https://demaine.org/wp-content/uploads/2022/04/lustre-ceramics-monthly.pdf Health and Safety and Overglaze (in particular lustres) https://demaine.org/wp-content/uploads/2022/04/health-safety-and-overglaze.pdf Health and safety in ceramics is always an emotive issue and I am well aware that it is up to the individual to become acquainted with the potential hazards and the risks associated with the materials and work methods employed. Ultimately we all have to take responsibility for our own actions. The options available can be discussed under the following headings • Substitute materials/work practices • Dilution ventilation • Local ventilation • Personal ventilation Unfortunately lustres contain solvents and there is no safe way around this apart from switching to reduced lustres. Dilution ventilation means having windows open and a fan drawing the fumes away from the workplace. This is satisfactory if only small amounts of lustre are being used. Local ventilation means a booth constructed over the workplace drawing the fumes away. Personal ventilation is the use of a respirator while working. My method of protection from fumes is as follows. I use a fume booth constructed by my husband together with a respirator while I have developed a method of working that limits my exposure to the hazards involved. I use a resist method whereby I estimate that 90% of my time is spent using lustre resist which is quite inert. The other 10% is the actual application of the lustre, as all the fine lines apart from some gold pen work is achieved by resist. I am confident that I am limiting my exposure to lustre.

Just to remind you that volumetric blending is sometimes helpful. If you wanted to make test tiles with 1.5%, 2.0%, 2.5% & 3.0% SiC you could mix up 4 glazes, or you could mix up a 3.0% glaze and "dilute" it with commercial glaze. You can then make a smallish quantity of an x% glaze by mixing 1 volume of the 3.0% glaze with (3.0/x)-1 volumes of the commercial glaze. (I would use a small syringe). Obviously this is an approximation, which assumes that the volume of SiC is negligible. 1.5% = 1:1, 2.0% = 1:0.5, 2.5% = 1:0.25, 3.0% = 1:0

+1 Would it be easier to use Brongniart's formula? http://www.potteryatoldtoolijooaschool.com/brongniarts_formula_made_easy.pdf A popular way to measure specific-gravity/relative-density uses a plastic syringe. https://ratcitystudios.com/blog/2017/11/14/specific-gravity PS If you cannot measure grams on your scales you will want to calculate the weight of water to fill the syringe. https://www.rapidtables.com/convert/weight/gram-to-ounce.html

You might also be interested in this Service Training Manual. Skutt:Troubleshooting Theory https://skutt.com/images/Error-Codes.pdf