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PeterH

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Everything posted by PeterH

  1. Sorry, I don't seem to have made myself clear. I'm thinking of a power-side that consists of - 3 x 208V elements - a power relay for each - the complexities/cost of a transformer. Seems likely to be as least as simple in the boxes as Neil's 1st & 2nd options to fix the 250V safety issues, and would presumably allow per-zone control if required.
  2. Have you tried an indian-ink test? Easy enough to wipe off if there are no cracks. My first crackle glaze was pre internet and I very much had to guess the recipe. Came out without a crack in sight. Thought well I've got the indian ink so lets see, lo and behold lots of crackle.
  3. Would a 208V 3-phase to 208V single phase conversion have any attractions? Need a big transformer of course.
  4. I have a very imperfect recollection of an idea that might be repurposed to help. I think somebody needed to remove pots from the bat "early" to avoid drying issues, but was distorting the pots when doing so. The solution was to put high-wet-strength paper (teabag paper) on the bat before throwing the pot. When the pot was dry enough: wire-cut under the paper and then pull on the paper to slide the pot off the bat without touching it. If the OP is dead set against bats, maybe paper could be used as a partial substitute? PS I seem to remember the teabag paper was available in 6" rolls (or was it squares). No idea of current availability. ... well at least somebody sells it https://www.thatscrafty.co.uk/thats-crafty-surfaces-tea-bag-paper.html https://www.vycombe-arts.co.uk/onlineshop/prod_3687465-Tea-Bag-Paper.html ... most hits seem to be for huge rolls of ill-defined product for commercial use https://tinyurl.com/5x2yt4sj PPS Obviously there must be a knack to get enough clay under the paper before you start throwing.
  5. So is it likely that both the new and the (rewired) old kiln could share an (installed to code) NEMA 6-50R socket? ... really what should be considered/needed for house re-wiring for both kilns, if the rewired one will be 10KW at 240V (~42A). [To be confirmed when more details emerge.]
  6. My thinking was that the 48/1 -- on the plate about replacement elements -- was consistent with 3 x 208V elements which -- if wired in parallel -- would be a 48A single-phase load giving 10KW. On the other hand I read the main plate as saying 3-phase (PH/HZ 3/60). If the plug was factory-installed it is highly likely to be within code (in some context). My knowledge of 3-phase practice only goes as far as knowing √3 is a magic number, and 16*√3 = 27.7
  7. Just sharing my confusion about US power supplies. All NEMA 14 devices offer two hots, a neutral, and a ground, allowing for both 120 and 240 V when supplied by split-phase power, or 120 and 208 V if the supply is three-phase. Might we be talking about a 208v 3-phase kiln? 3-phase would imply 3 208v elements each generating 10000/3 watts. For each element i=W/V = 10000/3/208 = 16A per phase. So 48A in total.
  8. Is this "Laguna MS-29 Clear Bright Glaze",? If so in https://www.axner.com/lagunams-29clearbrightglazedrysoldperlb.aspx points to Laguna's general dry glaze mixing instructions in https://4e1a0199-e3cb-4bc6-9d1a-f62c39960aec.filesusr.com/ugd/e5330f_6bae0b4596374aa7960ca367393ac0db.pdf Where it says Approximately 8 to 11 ounces of water per pound of dry glaze will be needed, but the amount needed varies per glaze. ... For specific recommendations on how much water to add call 1-800-4Laguna I make that a ballpark of 9.5 oz water to 16 oz dry-glaze. So there are 100gm of dry-glaze in 100*(16+9.5)/16 gm of made-up glaze (~160gm). Can someone do a sanity check on the figures.
  9. Not competing with Neil's excellent suggestion, but an example using wire. The Nichrome Wire Solution: An Alternative to Raku Tongs Makes Raku Firing Large or Lidded Pots Easy https://tinyurl.com/539u7ky2
  10. Which ball-clay are you using, and do you have a choice? Organic Matter in Clays: Detailed Overview https://digitalfire.com/article/organic+matter+in+clays%3A+detailed+overview Note: According to F. Q. Al Khalissi e W. E: Worral (Trans. Brit. Ceram. Soc., 8,1982,pag.145) organic substances can be completely removed by treating the ground clay with water oxygenated at 30% vol. and heated for several hours at approx. 80 C. https://www.potclays.co.uk/ball-clay-twva?search=ball clay PS Have you checked for black-core? PPS LOI looks like a simple way of checking the level of organics in your ball-clay. PPPS Would pre-burnout of some of the ball-clay as a power help? A thought inspired by this comment in https://digitalfire.com/material/ball+clay Ball clay typically does not comprise more than 30% of a body recipe so its opportunity to burn away is sufficient.
  11. At low concentrations, gaseous carbon dioxide appears to have little toxicological effect. At higher concentrations it leads to an increased respiratory rate, tachycardia, cardiac arrhythmias and impaired consciousness. Concentrations >10% may cause convulsions, coma and death. A few of the sites I used to visit had equipment rooms with CO2 flooding in case of fire, and took the dangers quite seriously. I think somebody had died in an incident at another company.
  12. Apparently yes https://www.mondaes.com/products/wonderwhitedryclaycone06 I cannot see a part number associated with it by this supplier. https://www.georgies.com/pdfs/catalog/Page PDFs/01-9.pdf But part number is CCD547
  13. Can you take a much higher resolution picture of a few of the spots? The fine-detail might give somebody a clue about their development. PS There seem to be a few low-density regions in the spotting, does that say anything about glaze/spot application (or movement)?
  14. That's a bit clearer, but I'm failing to see how the main pour could distort the shapes or lead to bleeding between the two slips. Are you certain that some of the slip in the main pour isn't infiltrating between the shapes and the mould? Perhaps you could scratch an unsuccessful casting to examine the 3D structure. If that's the case you might find this of interest Inlaid Slip Casting https://tinyurl.com/2j6ubnue
  15. Are you trying to do something like this? Or like one of these? Slip Casting Molds: What are they, why use them and how to achieve different aesthetics. https://www.jennyrijke.com/blog/slip casting molds different aesthetics-
  16. If it helps anyone understand things: The new relay 20850-81 is described in https://deltrol-controls.com/sites/default/files/pdf/data-sheet/270-275 Series Data Sheet.pdf under Model 25F Coil 24VDC on p4 (DPST-NO of I've read it right) The only reference I could find to the new old relay 23640-70 was in the "View all part numbers" list at https://deltrol-controls.com/products/relays/power-relays/275 Maybe Detrol could clarify the picture, or confirm the identify of a plug-in replacement?
  17. From Bisque Direct's mug page https://bisquedirect.com/bisque/mugs.html Earthenware Clay - Glazing and Firing. The recommended glaze firing temperature is 1000˚C to 1080˚C and soak (hold) 30 minutes + for all our Earthenware bisque items. For tableware items firing 1030˚C to 1080˚C produces a more durable product. Which is repeated on their dipping glaze page https://bisquedirect.com/glaze/clear-gloss.html They offer three glazes all firing "Approximately cone 06 to 05." Also gives Bullers ring ranges for each glaze.
  18. @Kate in Kentucky only This report on somebody having trouble with a "stuck" thumb-wheel seems to provide some insight on how it's supposed to work (and how to try to unstick it) https://www.yellowcottagestudios.com/manually-firing-my-cress-kiln/ Also this posting I'm under the impression that when correctly setup the thumb-wheel turns automatically with a speed (or profile?) governed by the speed control.
  19. For comparison with the roasting temperature you unearth the TG curve (red line) in this diagram seems to be a loss-on-ignition curve for colemanite: Figure 3: DTA-TG analysis of colemanite powder from https://tinyurl.com/v8z3nas2. The page you referenced stated that by 1750F the colemanite is almost melted... [1750F ~ 954C] PS The decrepitation seems to be analogous to a crystal-lattice-scale version of pots exploding because the chemically-combined water cannot escape quickly enough. Thermal decomposition of colemanite https://tinyurl.com/yz7u8u9v Thermal decomposition of colemanite Ca[B3O4(OH)3]H2O monocrystals has been investigated by thermal, X-ray, IR and optical microscopy methods at normal as well as at elevated temperatures. Investigations have revealed that thermal decomposition of colemanite occurs in the whole volume of the crystal and is divided into two independent stages: (1) formation of H2O from OH groups and (2) breaking of H2O and borate chains bonds and then removal of both kinds of water from the anhydrous phase of the preserved borate structure. Each process corresponds to a separate DTA peak, the second being accompanied also by loss of weight due to explosive water escape. This represents a rare event of dehydroxylation with distinct separation of H2O formation and removal of water molecules from the parent substance.
  20. From glancing at a few cement papers sucrose/table-sugar works better than most [all?] the common sugars, presumably because its shape and charge distribution help it make good "contact" with the surfaces it effects. On the other hand sucralose doesn't seem a major change in shape (no idea about change in charge distributions). Probably worth repeating Callie's 2.5g test with sucrose and sucralose? PS The bond for the Cl on the left seems to have changed from into the plane of the paper to out of the plane. https://www.thoughtco.com/wedge-and-dash-projection-definition-602137 A wedge and dash projection is a drawing, a means of representing a molecule in which three types of lines are used in order to represent the three-dimensional structure: 1. Solid lines to represent bonds that are in the plane of the paper 2. Dashed lines to represent bonds that extend away from the viewer 3. Wedge-shaped lines to represent bonds oriented facing the viewer PPS Looking up the Molar Masses in wiki suggests that molecule-for-molecule substitution requires 1.16 the weight of Sucralose. Looks like ~27% of the weight of Sucralose is chlorine.
  21. @Chris Campbell Care to comment? I cannot find your earlier post on soda ash (I think it started with you looking for a soda ash substitute).
  22. This paper seems relevant, a one-line summary is: ... sugar not only alters the rate of cement paste hydration, but the microstructure of calcium-silicate-hydrate (C-S-H) as well. New insights into the effects of sugar on the hydration and microstructure of cement pastes Can be downloaded (hopefully securely!) from: https://fdocuments.in/download/new-insights-into-the-effects-of-sugar-on-the-hydration-and-microstructure The effects of adding sugar to cement paste on hydration and microstructure were observed. While 1% sugar delayed hydration as expected, the delay period was shortened by increased curing temperature. When samples containing sugar began to react, hydration progressed very quickly and the degree of hydration soon surpassed that of control samples. Sugar addition increased the surface area and altered the pore size distribution, as measured by nitrogen, of cement pastes. Results indicate that sugar not only alters the rate of cement paste hydration, but the microstructure of calcium-silicate-hydrate (C-S-H) as well. PS I'll also give a couple of tiny quotes from another paper: Reactions and Surface Interactions of Saccharides in Cement Slurries https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.464.7279&rep=rep1&type=pdf Specifically, sucrose is stable in alkaline cement slurries and exhibits selective adsorption at hydrating silicate surfaces ... In the presence of additives such as saccharide molecules,cement hydration is known to be even more complicated.
  23. Found on Pintrest: ... and https://ceramicartsnetwork.org/ceramic-recipes/mid-range/richard-buschs-nutmeg/
  24. Can you be a little more specific? PS Best I could find was: T. Lam, G .L. Wynick, and W. M. Carty, “Melting Behavior in Traditional Ceramics”. J. Am. Ceram. Soc. 90 [3] (back cover). Publications. 5 pages ... although the significance of "(back cover)" escapes me Expecting to be able to access the abstract online I looked at vol 90 issue 3 and failed to find any trace https://ceramics.onlinelibrary.wiley.com/toc/15512916/2007/90/3 An author search for the most distinctive author name returned 0 results for "Wynick" in Author published in "Journal of the American Ceramic Society"
  25. If it's mica, are we assuming that it's added to the body? Certainly sounds easier to get a compatible collections of bodies that way. For cone6 it's probably worth reading Digitalfire on Mica https://digitalfire.com/material/mica Data sheets for various mica products quote a wide range of decomposition and melting temperatures (as high as 1800C for melting and 1500C for decomposition). A typical melting point of muscovite is around 1250-1300C. However there are many different kinds of mica. Thus it is impossible to give a formula and difficult to give a general chemistry (micas are never employed in ceramics for their chemistry anyway, the mineralogy of the material is what is important). Doesn't look too promising for cone6 but there are interesting comments on grain/platelet size so I'll continue. An example of how a small addition of mica affects the fired appearance of a terra cotta clay. The effect is still working at cone 03 (left) but is more commonly employed at cone 06 (right). Notice that it is still visible even under the glaze. This body is popular on the west coast, it was designed by D'Arcy Margesson. Standard grades of mica are too fine for the effect, this is likely Custer LCM Drilling Mud Mica. No idea how that Sourcing might be an issue, are there retail outlets for these products? A Following links from the Digital page give a little more information, and even a a page to request a small (1lb) sample -- presumably aimed at companies intending to order large quantities. For CusterMica : Analysis https://digitalfire.com/material/custermica Custer Drilling Mud Mica - gets to an error page not found on Pacer site Products->MuscoviteMica->LCMMica give overview and sample request option
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