PeterH

One line of thought The quest for the illusive leaf bowl: John Britt describes his search for an ancient technique. https://tinyurl.com/7bfmn6fc ... with the intriguing content Then, while on Facebook, a Japanese woman named Mia Ishiguro (no relation to Munemaro) noticed that I was researching the leaf bowl and having trouble, so she sent me the symbols for 'leaf bowl' in Japanese. ([TEXT NOT REPRODUCIBLE IN ASCII]) I copied and pasted these symbols into Google and found a lot of information, unfortunately written in Japanese, which I cannot read but, being a visual learner, I decided to click 'Images' and voila--thousands of images of the leaf bowl instantly appeared. I started to click the links and many connected to museums and historic books, while others led to blogs of people who, like me, wanted to figure it out. Several others led to newspaper articles allegedly describing the technique. I was excited, saved these articles and printed them out. Although I could not read them, I could deduce what was being done by the pictures. Today Google will translate text for you but not images and some of these were photos of newspaper articles. Nevertheless, this gave me some excellent techniques to try. Google translate gave leaf-bowl => リーフボウル Which sadly gives lots of images of leaf-shaped bowls! Printer friendly version at https://www.thefreelibrary.com/_/print/PrintArticle.aspx?id=372884215 The article appeared in print (no idea about the Japanese symbol) Ceramics Technical ISSN:1324-4175 Issue:38 Page Range:84-88 First Page:84 Last Page:88 John also sold an ebook containing this and other articles, don't know if it's still available. Not here, but some photos https://tinyurl.com/mvmnu3xf Guarded praise from J Baymore ... PS An historic example at https://www.britishmuseum.org/collection/object/A_1973-0726-279 PS Google translate into Chinese (traditional) gave leaf bowl => 葉碗 A google search for images then gave a few hits, the first of which was https://m.fei123.com/10000/4218.shtml

Suggest you post a picture of the label with kiln model number etc for the experts. PS If you haven't found it already this may be helpful https://www.cressmfg.com/resources/ especially Kilns - Instructions Manuals (and parts replacement guides) Kilns Diagrams Kiln Price Lists (both kilns & kiln parts) Looks like a Firemate controller, which does have relays (and infinite controllers switches, it's an ingenious design). PPS Can you guesstimate how many firings you've had? Do you regularly fire to near your kilns maximum temperature?

I'm way out of my field, but the term "farm duty" on the recommended motor raises a few alarm bells about the necessary "robustness". BTW the motor originally used may now be discontinued (C63KXGLD-4575?) https://www.grainger.com/product/DOERR-High-Torque-Farm-Duty-Motor-4K034 ... their suggested non-identical substitute is $255

Tony has a page on different mixers Propeller Mixer https://digitalfire.com/glossary/propeller+mixer Do you mean one described there or something else? If so, perhaps you can give the url where you saw it?

From the archives

Cheaply available second-hand, adjust this search for your location and currency https://tinyurl.com/mw873skd I found the second half of Ian Currie's book - which examines several important glazes -- very interesting. Especially as it reflects that there are many mechanisms that make glazes interesting. Online at https://wiki.glazy.org/t/ian-curries-stoneware-glazes/367

LOI (Loss on Ignition) https://digitalfire.com/oxide/loi

As an example here is the entry on cracks http://ceramicsfieldguide.org/pdf/materials-handouts/ClayCracks.pdf

Historical aside Code stone. Sold as an artificial stone, it was really a ceramic with a very narrow firing range. Coade stone https://en.wikipedia.org/wiki/Coade_stone The Secret of Coade Stone https://tinyurl.com/y2ckdhyy What is Coade stone? https://tinyurl.com/2s3b5j76

Naming an issue, see https://en.wikipedia.org/wiki/Calcium_phosphate Tricalcium phosphate (tribasic calcium phosphate or tricalcic phosphate, sometimes referred to as calcium phosphate or calcium orthophosphate, whitlockite), E341(iii) (CAS#7758-87-4): Ca3(PO4)2 https://tinyurl.com/bdds5ssf

Scarva offer it at a higher price, but lower postage. No claim this is best UKish price available. https://tinyurl.com/2t33eypa Partially completed order for 1kg

My understanding was that everything for sale is probably mined as hydroxyapatite, but sold as either triphosphate or synthetic bone ash. Two recipes:

I think the recipe is essentially the same, substituting calcium triphosphate for bone ash. Bone china https://digitalfire.com/glossary/bone+china True bone china is a special type of translucent porcelain. Instead of feldspar as a flux, bone ash is used (today available in synthetic form tri-calcium phosphate). ... my note tricalcium phosphate is Ca3(PO4)2 Unfortunately the terminological plot thickens: Phosphate Triphosphate https://en.wikipedia.org/wiki/Tricalcium_phosphate Most commercial samples of "tricalcium phosphate" are in fact hydroxyapatite Bone Ash https://digitalfire.com/material/123 Bone ash is TriCalcium Phosphate in the form of Hydroxyapatite Ca5(OH)(PO4)3. This reacts when making bone china to give Anorthite (CaAl2Si2O8) and Ca3(PO4)2. 2*Ca5(OH)(PO4)3 --> 3*Ca3(PO4)2 + Ca(OH)2 So I've no idea if you you substitute 1:1 hydroxyapatite (sold as calcium triphosphate, or maybe synthetic bone ash) for "real bone ash". But it probably isn't far off.

I can think of two possible reasons 1) Historically that's the way bone china was [always?] produced commercially. 2) You may only get marginal transparency gains from using bone china unless you make thin and fire close to warping. When you do - you need setters and hence a high bisque. If you don't - porcelain and white-stoneware are easier to use.

... while waiting for the experts to arrive. Sasha Wardell is an artist who works in bone china, her site is at https://sashawardell.com/ Her 1st book Slipcasting contains some bone china specific information. I haven't seen her 2nd book Porcelain and Bone China but I expect it's well worth reading. She gives an overview of porcelain vs bone china in Tempting Transparency https://tinyurl.com/mryx92z7 You need to high fire first because bone china has a short firing range and tends to warp. It's usual to use setters the support the work during this firing. Obviously you cannot glaze the parts the setter touches, so glaze fire afterwards. Glazing the vitrified body is difficult. Heating the pots helps, as does spraying. Tempting Transparency https://tinyurl.com/mryx92z7 Bone china has a low-glaze cycle following low-fire clay temperature ranges. The pieces need to be warmed up, usually to about 212°F (100°C) prior to glazing. This helps to evaporate water from the glaze slurry as it’s applied to the piece. When glazing, I pour glazes on the insides of the ware to line them and if I glaze the outsides, I spray them. Use a thicker application of glaze with a drop or two of gum Arabic added to the glaze to help with adhesion, as the body will have vitrified during the high firing. Bone China https://digitalfire.com/glossary/bone+china The process is completely different than what a potter would do: Bisque fire, glaze, high fire. Bone china is bisque fired to high fire and then glazed at a very low temperature. Since the porcelain has zero porosity, getting a glaze to stick and dry on it is not easy, the process needed goes well beyond what a normal potter would be willing to do. PS If you are not using setters, then I don't see why you cannot do a normal-ish bisque firing.

Might be worth snipping the resistor out and trying to clean it with an abrasive cleaner. PS It's a long time since I read a resistor, quick recap. Resistor Color Code Chart https://tinyurl.com/5n6ud78n A handy tool for reading resistor color code values https://tinyurl.com/5n6ud78n

... also see Power caulk gun to extruder conversion https://community.ceramicartsdaily.org/profile/894-pres/

@liambesaw You seem to be joining plastic handles to slip-cast pieces. Any comments for this thread?

Two page article (as jpegs) by Preston Rice & Madeleine Coomey ? https://1.bp.blogspot.com/-xYr-ZLHHRyc/XGsvzDufnKI/AAAAAAAAA0U/zISVLs-TKzQ3RPNKwFoc2rZ4CNnpzi3iQCLcBGAs/s1600/TT_RiceCoomey.jpg https://4.bp.blogspot.com/-6bczNxLZFgI/XGswHUKVTOI/AAAAAAAAA0c/K5DZtUz323YGyY0UNfsVDQCP0k-LhPtRgCLcBGAs/s1600/TT_RiceCoomey2.jpg From https://picworkspottery.blogspot.com/ (Pres's site?) Also as Tips and Tools: Extruder Conversion https://tinyurl.com/47cbbuv9

I don't think anybody has directly addressed this question. Understanding the Deflocculation Process in Slip Casting https://tinyurl.com/2p96x33r A simple mix of clay and water will not work well at all for casting. Not only will it quickly waterlog the molds but it will shrink too much (and therefore crack in the molds) and it will take much to long to cast. It will also gel and settle out and generally make the process miserable. Optimal casting requires that the slurry have minimal water content (e.g. 30% instead of 60%), good flow and draining properties and that it not settle out or gel too quickly. When the slurry is right the casting process works amazingly well. ... I suspect that these issues are amplified if you are trying to solid-cast.

Different methods of making handles for mugs https://tinyurl.com/yckrtf6r Video: https://tinyurl.com/mrnwfa5b

a sprig mould?

Which reminded me of an early paper on local reduction. One of the most interesting ideas was the use of a SiC containing engobe/slip which then influenced the colour of a SiC-free glaze applied over the bisqued piece. - They give combinations for copper reds at cones 012 and cone 9. - They suggested that silicon carbide achieves reduction effects over this remarkably wide range by only reacting when in contacted with liquid glaze. I haven't seen this idea mentioned elsewhere (and would be very interested in pointers). More detailed summary of the 1932 paper in an earlier post PS If the slip idea does work I wonder if an SiC/CMC "underglaze" would also work. PPS A full copy of the paper is now online via https://ur.booksc.eu/book/9078584/3dc696 PPPS I get the english version of this paper using this button ... your mileage may vary. If so see the later posts from those who had difficulties..