PeterH

Opened OK for me, try this URL instead https://community.ceramicartsdaily.org/applications/core/interface/file/attachment.php?id=15303

I was asking if you changed your casting process to make the seat significantly thicker would the seat then be less inclined to slump on firing. Two ways to achieve this increased thickness might be: 1) After emptying the mould immediately add enough slip to - say - double the final thickness of the seat. 2) Only partially empty the mould and let the remaining slip increase the final thickness of the seat.

The flat surface with holes that you sit on. Didn't want to say top because of the possibility of bisque-firing inverted.

A question rather than a suggestion. What would be the effect of casting the seat thicker than the sides (by manipulating the slip level)?

https://ceramicartsnetwork.org/daily/article/A-Colorful-Variation-on-the-Naked-Raku-Firing-Technique After the bisque, we apply the resist slip and glaze combination that gives naked raku its special look (Figure 3). For the resist slip, we brush on a thin layer of our Amador throwing clay. It holds on to the pot very well throughout the process and comes off with ease after reduction. We have experimented with making the resist slip from lots of different stoneware clays with excellent results. Be sure that the pot does not feel too “cool” to the touch before glazing. ... my emphasis, maybe Amador has no unique/special properties (except already being used by the Jacobsons).

While registration is required to access info from minarikdrives.com a google for Minarik Drives XP Series User Manual gives two freely-accessible manuals on another site. Minariks DC Drives - XP-DC Series - User Manual https://www.galco.com/techdoc/mnrk/xp08-60dc_um.pdf (44 pages) MInarik DC Drives - XP-AC Series - User Manual https://www.galco.com/techdoc/mnrk/xp10-115_um.pdf (32 pages) I've no idea of their status relative to current or historic versions of the boards. Note that both MAX SPEED and MAX SPD are used, so allow for this when searching the documents.

Having difficulty finding the full firing range for "sax trueflow glaze", but this https://www.amazon.co.uk/Sax-True-Flow-Gloss-Glaze/dp/B0044SCR6O says Dinnerware safe when fired to cone 06-05 (so cone 08 seems low).

Nice, and very haunting. There does seem to be an issue in getting enough iron deposited to form a good image when fired, let alone high-fired. I came across this thread which may be of interest How to improve density in Cyanotypes? https://www.photrio.com/forum/threads/how-to-improve-density-in-cyanotypes.175947/ ... I haven't read it all, but it contains interesting snippets such as This tonal reversal is the phenomenon of ‘solarisation’ first observed and named by Herschel. It is actually desirable for making a print-out image, because it can ultimately yield a higher maximum density: the self-masking action by the Prussian blue in the shadow regions of a printed-out image is diminished by the reversal to white, which allows the ingress of more light and formation of more (white) product. After the exposure, the Prussian white so formed is oxidised back to Prussian blue, either slowly by the oxygen of the air, or more rapidly by including a bath of an oxidising agent, such as hydrogen peroxide or a dichromate, in the wet-processing sequence: Prussian white + hydrogen peroxide ---> Prussian blue + hydroxide ions. ... my emphasis It also mentions Mike Ware, who I hadn't heard about before. He is "a chemist and photographer who has spent part of his career updating old photographic processes". As he is a member of the Royal Society of Chemists this looks like it would be an in-depth study. wiki: https://en.wikipedia.org/wiki/Mike_Ware_(photographer) Home page: https://www.mikeware.co.uk/mikeware/main.htm The new cyanotype process: https://www.mikeware.co.uk/mikeware/New_Cyanotype_Process.html 406-page downloadable book on the cyanotype process (including lots of history): https://www.mikeware.co.uk/downloads/Cyanomicon.pdf

Oops, I was completely mislead by the controller's manual stating that "the controller will display PF when first plugged into an outlet". Especially as elsewhere it clearly indicates that the switch should be in the off position between firings. Apologies to the OP @socrasoup

Interesting ... This may be the same reaction New Positive Siderotype Process using Iodine/Starch Colorant https://tinyurl.com/5zda5fmv This "development" process looks like a variant of the starch/iodine test, and IMHO the iodine complex is pretty sure to burn out. Just FYI Sanity check: Iodine does indeed form a blue complex with PVA (which is in the Elmers glue used in first reference). https://link.springer.com/chapter/10.1007/3-540-56579-5_3?noAccess=true

ChoCoLate from New Mexico Clay https://nmclay.com/chocolate-clay

The kiln should have been left with the "safety switch" turned to "off". Can you confirm that it was back "on" before this test? From The Safety Switch https://paragonweb.com/wp-content/uploads/IM-126-DTC-600C-DTC-600-Instructions-1.pdf p1

Kiln and controller types models?

Don't think anybody has mentioned applying excess wash and then sponging it off to emphasise texture yet.

Do @Bill Kielb's tests first. PF is a controller display DCT 600 manual https://paragonweb.com/wp-content/uploads/IM-126-DTC-600C-DTC-600-Instructions-1.pdf My naive interpretation is that it could just be "finger trouble" Or else it requires working through a list of probable causes. See p1 To Begin, display IdLE p1 The Safety Switch p4 Controller Displays PF. PS I find a fuse resistance of 4.2ohms difficult to credit, they are designed to be near zero resistance or open circuit! Two possible explanations are: 1) The resistance is really zero but there is some in-circuit corrosion whose resistance is also being measured (cleaning contacts and measuring out-of-circuit reduces the chance of this). 2) The measurement was taken with a meter not really up to the job (especially a poorly-calibrated analogue meter on a scale intended to read much higher resistances). ... Although when I've been in this position I asked myself "is the fuse open-circuit" rather than "what is the resistance of this fuse". Not open-circuit => fuse not blown (usually).

Just to emphasise that the "height" of your final mould can more than the "height" of your cottle boards. Not least because it may be easier to create multi-part moulds this way.

That doesn't seem consistent with the figures in http://www.skutt.com/pdf/service_manual/11_4.pdf OTOH the wiring diagram https://skutt.com/images/KMT714-W_8510.pdf shows one element across the L1/N split and two elements in parallel across the L2/N split. If the socket is fed from a split-phase supply these voltages are 120V (if the socket is fed from a 3-phase supply they are 108V). If all three elements are 11.7 ohms this gives power consumptions of 3,692W & 2,990W (close to the published figures of 3,600W & 3,000W). I can find no combination of 11.4 & 5.7 ohm elements which gives comparable power consumptions.

Confused thread about the two versions of the kiln Although Mop (a UK resident) seems to be talking about 13 & 16 amp 230v versions, rather than the 208 & 240v US versions. Anyway, the UK versions have max cones of 8 & 10, which will effect the element lives when firing high. What cone do you glaze-fire at? The US versions (which both have the same element resistances but different voltage feeds) look like they have similar differences in power -- and presumably max cone rating. PS Slightly surprised to see the UK classified as 230v rather than 240v, but I was forgetting about the great non-standardisation. The voltage used throughout Europe (including the UK) has been harmonised since January 2003 at a nominal 230v 50 Hz (formerly 240V in UK, 220V in the rest of Europe) but this does not mean there has been a real change in the supply.

Minor insight in PS, the rest is just cut & paste of potentially relevant facts. Looks like DIAG is used to indicate the kiln's diagnostic tests, which include VOLT. https://skutt.com/skutt-resources/troubleshooting/diagnostic-tests/ Specification sheet https://skutt.com/pdf/service_manual/km_kiln_specs.pdf ... which seems a little economical with the truth. - Will fire with 240V or 208V power. - should never be fired on a 240V supply without first installing a full set of 240V elements. Wiring diagram (without element resistances) https://skutt.com/images/KMT714-W_8510.pdf BTW the element resistances for 240v & 208v might be the same! PS It might be interesting to use the AMPS feature in the dIAG (if fitted)? Am I right in thinking that the current resistances of the elements are given by VOLT/AMPS(1), VOLT/AMPS(2) & VOLT/AMPS(3)? http://www.skutt.com/pdf/service_manual/11_4.pdf

Pure & Simple suggest https://cdn.shopify.com/s/files/1/1130/0194/files/INSTRUCTIONS_2021.1.pdf?v=1609298598

Thread on pancake opening ...

Would adding an "inert" stain to the commercial glaze serve your purpose? I suspect stains consisting of spinel pigments would be suitably inert, although obviously check the small-print. For example Mason 6600 best black 6600 https://www.masoncolor.com/ceramic-stains/blacks/6600-best-black). reference notes https://www.masoncolor.com/reference-guide >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>^^^^ Don't know how serious the advice "Use only as a body stain" is. For example https://www.scarva.com/en/gb/Mason-Stains-By-Mason-Color-6600-Best-Black-Stain/m-2170.aspx Our range of Mason colours with over 60 ceramic stains can be used in a wide variety of cost-effective applications. All stains in this revolutionary new colour system contain NO LEAD and can be used as glaze stains ...

- If there is iron in the recipe I would strongly suspect that it's there to alter the redox chemistry. - OTOH from what I've read tin increases the solubility of metallic copper in the glaze - aiding the formation of copper colloids/nanoparticles. Suitable redox conditions are necessary but not sufficient for this. [Digitalfire points out that lead, bismuth and zinc may also act as solvents.] - Although orchestrating things to end up with suitably dispersed nanoparticles of the right size at the right time ( in the cooled glaze) remains elusive. And there may well be several different redox/solubility paths to achieve this. It's worth noticing that the formation of copper ruby glass seems far better understood/managed. Probably because controlling the redox chemistry of a covered vat of glass is far easier than maintaining the redox chemistry of a thin film of glaze in contact with a changing kiln atmosphere. There are also a lot fewer variables to play with when experimenting. Most readers stop here, long ramble follows Substituting iron for tin I'm reluctant to comment on this, but it's a fair question so here goes. - Beside it's redox properties tin can be used to increase the solubility of metallic copper, and also to act as a colloidal protector of colloidal copper. Iron provide some redox properties, but non of the colloidal-enhancing./protective ones. - Several of the recipes in https://puttgarden.com/crystal/friends/tom-turner/9-9-09/cu-red-tc/art0003.htm contain red iron oxide. Interestingly the two with the lowest tin levels contain iron. - If you try any experiments I'd start substituting atom-for-atom. Confirm with wiki, but molar masses are SnO2=150.7 & Fe2O3=159.7 so for atom-for-atom use about half the weight of red iron oxide. - Personally I might try adding iron to an existing recipe first, and see what happens. Tin seems to be involved in keeping a lot of balls in the air https://digitalfire.com/article/copper+red+glazes In terms of composition, the glaze needs to be able to support the solution of Cu. To achieve this it needs to have things in it that are friendly to the presence of metal. The best of these is PbO - I can hear the gasps of horror now. Yes, that Godzilla of the Elements. Bismuth is another good option in some glazes, Zn helps and there is, of course, tin (Sn). Sn does a couple things. First it improves the solubility of Cu. Metals, per se, aren't really very soluble in glaze and if you can't get the metal dissolved, it can't very well be precipitated in any organized fashion. Second, on cooling, Cu tends to attract Sn atoms from the glaze. These atoms sort of "coat" the crystals as they are developed and thus serves to control their size by limiting the attachment of further Cu atoms to the crystal. This behavior is that of a protective colloid and it is of great advantage. Because if the crystals get big, the glaze turns "livery" looking, and the doughnut remains elusive. Third, to the extent that Sn has limited solubility in SiO2 or B2O3 based glassy material, it probably also serves to provide nuclei on which the coloring crystals can grow. Tin oxide is added to all practical non-lead Cu red glazes in amount way beyond what's necessary to promote good solution of Cu in the glaze - many compositions contain up to 4-wt%. Of course, if there's too much tin it doesn't all dissolve -- causing opacity. This may or may not be desirable. Tin is volatile at high temperatures and a lot of it leaves the very thin glaze film by evaporation. Compensating this evaporation is important to how much tin will remain dissolved in the glaze. This explains the large amounts of SnO2 in many reported glaze compositions. Some kilns have turbulent atmospheres and a larger amount of evaporation would be anticipated in these circumstances. In glassmaking, if you melt in a covered pot, in which evaporation is not an issue (in most cases), the amounts of SnO2 required seldom exceed 2 wt%. If you use too little Sn to promote the solution, Cu will precipitate on the spot with dreadful results. This is one of the reasons that application of the glaze is so important and why really thin films often fail to develop a nice red - when red color forms at all in a tin depleted glaze, it often has the color of liver instead of a crisp red. The amount of Cu necessary to develop a good red depends on how much of it can be dissolved. This depends on how much the glaze would dissolve on its own and how much this is improved by the presence of Sn. Many pottery glazes contain what I feel is a lot of Cu-oxide in the batch, but that's just an opinion. The best reds always contain the least amount of Cu. Reduction is the critical step in producing a nice Cu red. Note that some of the tin in the glaze can be lost by evaporation (especially high-fire & gas?) . By reducing evaporation you may be able to reduce the tin in the recipe without needing to substitute. Maybe some of the ideas here (to reduce the loss of copper) might also reduce the loss of tin? https://puttgarden.com/crystal/friends/tom-turner/9-9-09/cu-red-tc/art0003.htm One must be able to apply a red glaze fairly thickly so it can make it through the higher fire reduction periods without dissipating its copper content. There are all sorts of simple methods one can use to ease this problem: Brush on iron oxide over the glaze. This will help seal the surface at high temperature. Brush a thin solution of copper slip under the glaze. This will produce a barrier to hold in the copper. Fire the pot in a sagger that has copper carbonate brushed on the inside of it. This works to keep the copper gasses flashing back on the pot. Put a clear, slightly lower-firing glaze over the base red glaze. This acts in manner similar to the iron oxide but allows more color to come through. Add a small amount of silicon carbide powder to the glaze. This creates an internal reduction that dissipates less rapidly.

Nice discussion on copper/tin interactions in Copper Red Glazes https://digitalfire.com/article/copper+red+glazes Well worth reading the whole page, but the highlight is perhaps Sn does a couple things. First it improves the solubility of Cu. Metals, per se, aren't really very soluble in glaze and if you can't get the metal dissolved, it can't very well be precipitated in any organized fashion. Second, on cooling, Cu tends to attract Sn atoms from the glaze. These atoms sort of "coat" the crystals as they are developed and thus serves to control their size by limiting the attachment of further Cu atoms to the crystal. This behavior is that of a protective colloid and it is of great advantage. Because if the crystals get big, the glaze turns "livery" looking, and the doughnut remains elusive. Third, to the extent that Sn has limited solubility in SiO2 or B2O3 based glassy material, it probably also serves to provide nuclei on which the coloring crystals can grow. Tin oxide is added to all practical non-lead Cu red glazes in amount way beyond what's necessary to promote good solution of Cu in the glaze - many compositions contain up to 4-wt%. Of course, if there's too much tin it doesn't all dissolve -- causing opacity. This may or may not be desirable. Also of possible interest The Dual Mechanisms of Tin Oxide in Copper Red Glazes https://glazy.org/posts/168150

Only hand-waving, but I expect the importance of tin (and iron) in some copper glazes is because all three elements have variable valencies; and in the right circumstances can help redox reactions move copper from Cu(II) to Cu(I) or even Cu(0) -- and/or buffer it against oxidation once it's in the desired state. There is also Weyl's point that the presence of tin increases the solubility of metallic copper in a glass (or glaze), which can be important in obtaining colloidal copper particles. Woldemar A. Weyl Coloured Glasses has some interesting thoughts on the colouring mechanisms in glasses. Not cheap, but if you can borrow it on an interlibrary loan ...