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bny

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  1. I have two of the Paragon Caldera kilns with Orton digital controllers. They will run on a standard household circuit. It would be better to have a dedicated circuit installed with the most heaviest gauge copper wiring allowed by code. I tried running mine on an outdoor patio outlet distant from the panel, but this did not work well. Any energy that is not being dissipated inside the kiln, is being dissipated by the house wiring, and who knows how hot that is getting. I now run it on a garage outlet, which is the closest outlet to the panel. It will not run well on even the heaviest gauge extension cord; it must be plugged directly into the outlet. If you are having a new circuit installed, it might as well be 220V, which gives you a wider choice of kilns for cone 10. I am partially satisfied with these Paragon units with one notable exception: mine will make 2300 F only for around 6 firings. Both degraded to be reluctant to make even 2200 F in any reasonable amount of time. I replaced the elements in one, and the replacement elements also made only around 6 firings at 2300 F. The time to reach 2300 F increases with each firing. My work is technical (small wares dry-pressed from powder). I do not use a cone schedule, and instead typically run the kiln at full rate to the target temperature, with a designated hold time at that temperature. My most pleasing and technically best results come from a feldspar+kaolin composition that requires 2300 F. I have had to compromise the composition by removing kaolin, adding an organic or sodium silicate binder to replace the binding function of the kaolin, then adding one or another type of frit to get the firing temperature down to 1900-2150 F. This does not give a pure nearly translucent white result, but it is good enough to investigate most other aspects of the process. This without having to deal with sharp fragments of brittle used elements, and abuse of the delicate firebrick. Replacing elements in the close quarters of the Caldera, is not a pleasant process. It is possible that the Caldera would have a longer element life at higher temperatures, if it were on a lower resistance dedicated circuit.
  2. Print by what method? Laser print is only iron unless using special ceramics color toners. Even iron comes only from certain toners like HP LaserJet 4.
  3. I just put the feldspar and frit as-purchased into a plastic jar and shake to mix. I then tare-weigh a plastic cup, transfer the powder mix into that, weigh with container tare subtracted. I then calculate say 8% of that weight and add that much water with an ordinary misting bottle. Then mix with a popsicle stick and transfer to an ordinary unglazed porcelain mortar. Then use the pestle to mix so that the water is uniformly distributed. The mixture still is a powder but coheres somewhat and may form a sort of cornmeal texture. Scrape it out of the mortar into a sealable container or press now. Nothing special about the mortar - I got it at an art store. You might get different results by milling but I have not bothered. It works quite well without. Mix ratios and temperatures take some experimenting. To get a colored body I dry and grind one or another glaze to a powder and mortar grind dry before weighing in the water. Glazes tend to lower the required firing temperature, sometimes way too much. Fire on something expendable or on an alumina bed. I have not yet tried Mason stains or oxides directly in body compositions. The strangest result was from adding bone meal (nutritional supplement, not calcined bone ash). This gave ceramic foam with a closed glassy surface.
  4. Erratum: 73% G-200, 27% EPK dry weight. 10mg digital scales are inexpensive and readily available thanks to the gold trade worldwide and the weed trade in many regions. My typical batch is 10-20 grams dry.
  5. I was beginning to wonder if I might be the only person experimenting with dry pressing on a personal craft scale. My interest has been in reconstructing aspects of the process by which china buttons and beads were manufactured from circa 1847 until the mid-1900s. (Prosser process.) Starting point: 73% G-200 feldspar, 23% EPK. Mix the dry powders, weigh out a portion and moisten with a spray bottle to 6-9% water by weight then grind in a mortar. I press in a cheap Harbor Freight arbor press, no hydraulics. My typical ware is around 3/4" diameter. I use an ordinary oilite bronze bushing as a sleeve, and dies either improvised from hardware or machined from copper or bronze rod slugs or cast in epoxy by transfer molding from an original object. The pressed wares can be handled with some care. I sometimes hand drill holes with e.g. #51 drill held in the fingers. Also I smooth off pressing ridges and flaws by rubbing carefully with fingers. Fire at 2350 F at kiln's full rate of rise, hold maybe 20 minutes. They come out quite white. My little 120V test kiln elements only make 2350 a few times so I often add 3124 frit to get more survivable firing temperatures. Exploring one reported variant of the old process, I eliminate the EPK entirely, using G-200 and 3124, and add an organic binder. The old process was reported to use milk, but I interpret this as being casein. I use white vinegar to drop casein from milk then press the water out and resuspend in hot alkali solution (sodium carbonate) and dry down to something between slushy paste and quite dry. 70/30 G-200/3124 ad lib the casein, and 8% water will press and cohere, and give a white result around 1900-1950F.
  6. I bought some from japancrafts.com.au . Their web site has a page that gives instructions for applying the transfers. They worked fairly well for me, but I have made only limited use of them and on very small dry pressed wares that were bisque fired to only a quite fragile state. The seller above recommended 1100-1300 C firing. Dampen the ware with a lightly dampened sponge, apply the transfer, smooth down with a lightly dampened sponge, wait 2-3 minutes then cautiously peel the paper, laying it back down and sponging again if the color is not completely transferring. Too much water will dissolve and run the color. I read somewhere that these transfers may have a limited shelf life. There is video online showing similar transfers being printed in China. They were printed by intaglio from metal plates on small hand presses in a very rudimentary workshop.
  7. Buzzing and erratic operation could be from degraded filter capacitors in the DC power supply to the electronics. Capacitors, especially cheap electrolytics, are usually the first components to fail.
  8. For transfer printing tests I routinely refire white glazed wall tiles 4 inches square, made by Interceramic and sold by Lowes for a whopping 16 cents each. I fire to 1900F full rate in my little test kiln, taking a bit over 2 hours. They come out looking good as new. Sometimes I overglaze with a clear glaze from Gare. Not certain exactly which product, because I buy it in small amounts from a local studio workshop. If I let these cool too quickly I see some cracking of the glaze, but it does OK if allowed to cool in a closed kiln.
  9. bny

    Screen Printing

    Speedball framed screen, Speedball or Jacquard emulsion, Speedball or Duncan glazes, Coyote underglaze, Mason stain and frit in neutral screen print ink base. Proofs on ordinary paper did not look good and attempts to print onto decal paper were worse. I could not reconcile the fine feature sizes that I needed with the screen mesh and poor ink transfer through the screen. A design with larger features might work better. Stuff is mass produced this way (like the cartooned tea mug next to me), but with engineered specialist materials and processes.
  10. bny

    Screen Printing

    For a brief interval in the video below at time 2:44 you can see an example from Faiencerie de Gien, of screen printing to tissue paper, then transfer by hand onto a compound curved surface. https://www.youtube.com/watch?v=NpMzhOANjpQ Classically, the tissue transfer technique used engraved copper plates, with a stiff oil-based ink, printed hot. There might be one commercial pottery who still do it this way (Burleigh). Screen printing gives some advantages, especially in wider choice of ink vehicles, and the possibility of using ordinary water-based glazes or underglazes. One problem is that the solids in glazes or mix-your-own colorants tend to be coarser than typical screen printing ink pigments. This could argue against using the more convenient pre-sensitized screens, and instead toward coating a coarser screen material with liquid photosensitive emulsion. My own results with screen printing were not good, but I did not persist at it. My objectives have been more toward understanding the old copper plate technique (reconstructing some industrial history) than toward creative expression.
  11. The Potclays tissue goes beyond "some promise" of soak-off release with no soap or other special treatment, and with the simplest ink vehicle: #8 burnt plate oil, no pine tar. It would be good to understand exactly why this paper works as well as it does.
  12. "Current transformer" very likely refers to a specific circuit component that is not the familiar step-up or step-down transformer within the power supply. A current transformer often looks like a plastic or ferrite rectangle (core) with a hole through the middle and a wire passing through the hole, or wound a few times around one leg of the rectangle. Another pair of wires will be connected to the circuit board. This is used to measure the AC current passing through the single wire, either as a part of a feedback control loop, or as a safety guard (cut off the power if over-current is detected), or both. It is also possible that "current transformer" is a misnomer for a DC current sensor that does the same thing with e.g. a Hall effect magnetic field sensor. (Transformers work only with AC, not DC, though they might be used with chopped DC as could be seen in a motor control circuit.) It is cheaper to just put a low-resistance (but high enough wattage) resistor into the circuit, and measure the voltage across that current sense resistor. Look for something resembling a rectangle with a hole and a wire through it, then look for bad solder joints, broken wires, or loose or corroded push-on connectors on the wires connecting that to the circuit board (the current transformer could be on the circuit board itself), or on the wire that passes through it.
  13. The idea of resurfacing paper is interesting; I might give it a try. I already have tried crayon-ing bar soap onto paper, and obtained poor results: uneven distribution of the soap, and poor ink take-up. Interactions between ink vehicle, ink solids, plate features, paper, and sizing are manifold and baffling. "Cicada wing" paper for example is alum-sized, takes ink beautifully without soap (less well with soap) but does not want to soak off even if soaped. Interesting behavior observed with the Potclays tissue: it shows some promise of soak-off release without soap sizing, at least with one of my inks.
  14. bny

    Deflocculated Wax Resist?

    "Mobilicer" is or was a Mobil Oil trademark for a family of wax emulsions, doubtless from "cera", Latin word for wax.
  15. In case someone is interested, there is one source who still sell a paper that they specifically call "pottery tissue": Potclays Limited, Stoke-on-Trent, item 5785-02. I just received some of this and have not yet tried it, but decided to give an early report. It is around 30 cm wide and appears to be cut to order length from a roll. It appears to be substantially similar to cigarette paper, but almost certainly without the whitener/opacifier additives (calcium carbonate, titanium dioxide) or combustion/ash modifiers that go into the paper for factory-made cigarettes. It differs from typical MG (machine glazed) tissue like medical table paper, in having both faces compact and smooth, but without either surface being glossy. It differs from roll-your-own cigarette paper in size and in not having a distinctive watermark (though it does have a faint rib or grid pattern, probably from a screen in the papermaking machine). The weight is comparable to cigarette paper. The width of this material suggests that it is or was specifically made for whatever might remain of the traditional transfer printing industry (Burleigh being perhaps the only survivor), who print from engraved cylinders. The width looks very much like what may be seen online from pictures of Burleigh's printing operation. I have found that smooth (not creped) medical table papers can work reasonably well for transfer. A distributor of this paper commented that it is a low-end commodity, and within his experience does not appear to be highly consistent even within their container-load lots. It is however quite cheap and readily available. I have also found that especially Elements Kingsize brand of roll-your-own cigarette papers (110 x 55 mm, so the design must fit within this constraint, and these are the largest papers that I can locate) are better at wash-off than anything else that I have tried to date, though they might not be as good at ink holding as medical table paper or sewing pattern paper. Amusingly, I have also found that wrapper paper from some types of individually wrapped toilet roll may be usable. I soap the paper by brushing with a fairly strong solution (cloudy/turbid at room temperature) of a locally made simple bar soap (Bare Bar from Swan Haven Soap, Petaluma, California), allow the paper to air dry, then iron against a glazed ceramic tile with a household clothes iron. Unlike what appears to be described in the old books, I do not print with the paper wet. Instead I print dry, with a slightly moist backer sheet of newsprint. I will post again once I have had a chance to try the paper from Potclays.
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