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Dick White

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  1. Zinc in glazes

    First, can you identify the strong acids in your glaze recipe? If not, then the problem of zinc solubility in the presence of strong acids isn't a problem. I don't know about your glazes, but mine tend not to have strong acidic properties. The bigger problem with zinc glazes is the unattractive way it interacts with chrome as a colorant. If you are in total control of the oxide colorants in your glazes, just keep chrome away from a zinc-bearing glaze. If you use stains, either in the glaze or in an underlying slip, you need to learn what oxides were used by the manufacturer to achieve that color. Mason publishes a reference guide, but other sources are a mystery. As for replacing zinc, that is a challenge. Zinc performs as one of the RO fluxes. But it also imparts other qualities to the glaze (opacity, surface durability) which are not easily replicated by swapping with other fluxes.
  2. Table top fountain design

    I agree with Neil, don't have any openings in the main vessel that will be below the water level in the reservoir. It will leak when you least expect it, and in the worst possible location. As part of the overall design, develop some sculptural elements around the edge of the vessel that can hide the cord. The particular element that will house the cord must be designed so that the cord tucks under it somehow, out of sight but still removable. The small pump will need to be removed periodically to clean the gunk that will inevitable clog the filter inlet.
  3. Genesis Controller

    I really like my Genesis. I bought it direct from Bartlett and built my own external wall-hung controller with it. The additional features and ease of use over the earlier V6-CF are worth the extra cost. The only thing I don't like about it is that Bartlett doesn't seem to have any idea how the customer side of a software company operates, in that they don't offer any information about the changes that are in each firmware update. The version number of the user document on their website can only be determined by the download filename, not printed on the cover page, and is an older version than was most recently installed, and thus I have no clue what new features are being installed in my controller when it updates itself other than a page-by-page line-by-line comparison of this document vs. the last one I happened to have collected. Neil, what can you tell us about the availability of this new mobile app?
  4. Why Calcine China Clay?

    China Clay and Kaolin are generic names that are often used interchangably. There are some specific technical/chemical differences between brands of kaolin, e.g., EPK, Tile6, Grollegg, but unless you are working with a highly nuanced recipe or situation, it probably won't matter which brand of kaolin/china clay was calcined and put in that bag.
  5. Updating kilns

    The power side of it is easy, though expensive, with an appropriately rated transfer switch. We have 2 of them in the community center studio where I teach. Handle up, 60A kiln plug on the left has power; handle down, 60A kiln plug on the right has power. We do that not for control purposes, but because there isn't enough power/circuits in the building to run both at the same time. A shared digital controller is going to be the issue. The thermocouple driving the controller must be in the kiln that is being powered by the controller. We can swap the power from one to the other with a switch (or manually unplug kiln A from the receptacle on the side of the wall controller and plug kiln B in), but swapping thermocouples from one kiln to the other (or installing a switch to change between 2 thermocouples in different kilns all the while ensuring that the thermocouple switch position matches the power direction) is a another kettle of fish.
  6. Updating kilns

    Depends on what you mean by "hook up." The controller panel in a wall-mount is the same as installed directly in a digitally controlled kiln, and can only turn one kiln on/off at a time. When such a controller is installed directly in a kiln, it turns the elements on and off as needed. If the controller is in an external wall-mounted box, it turns a plug on the side of the box on and off, and the old manual kiln is plugged in there, not into the wall socket, while the external controller is plugged into the wall socket. The manual kiln is turned on High for maximum heat whenever turned on, and the controller trips it on and off as if unplugging it for a few seconds and then plugging it back in for a few seconds (in tune with the relays clicking). On the other hand, with Bartlett controllers (regardless of the brand of the kiln, as many use the same Bartlett controller while other kilns use Orton controllers), you can get additional adapters for the digital controller in each kiln and computer software that will allow you to manage up to 50 individual kilns with controllers from a single central computer. I think Orton has something similar.
  7. Updating kilns

    The Electro Sitter is made by Olympic, but it isn't specific to only Olympic kilns. They have several models, based on the configuration of the Dawson Sitter it is replacing, e.g., one in a separate gray box (e.g., L&L) or one mounted in the wiring box (e.g., Skutt), long tube, short tube, etc. In addition to the reasons Neil gives, consider cost. Since you have 2 kilns, you can buy 2 Electro Sitters for ~$500 apiece, or 1 wall-mounted controller for ~$500. Either way, you apparently don't have an appropriate circuit, so you will have to install one, and then you will have to unplug one and plug in the other when you change kilns. Would you rather unplug/plug the kiln power cables into the plug on the side of the single external controller, or would you rather pay $500 more so you can unplug/plug the kilns into a plug on the wall. Either way, you are unplugging/plugging to change kilns. Or you could pay several hundred more and have the electrician install 2 separate 240V/30A circuits, and then you can run both simultaneously. For that, you would install the Electro Sitters so each has digital control. Finally, you asked about combining them into a single kiln. Yes it can be done. Should you do it? Probably not. If you did it, you would have a kiln that is twice as tall (and deep once you are inside) and likely to be next to impossible to load.
  8. what is your favorite wax resist?

    Any canned shellac typically used for woodworking will work, though there is no need to pay extra for the blonde/supper blonde varieties. Standard orange is fine as we don't care whether the finish will alter the natural color of the wood. An issue with shellac is it is alcohol based. You cannot wash out the brush in plain water, but must use alcohol solvent or - old painter's trick here - household cleaning ammonia for the initial cleaning of the brush.
  9. My sentiments exactly. In the glaze calc class I teach, I have a fully annotated step-by-step spreadsheet table to show all the details of the derivation of the unity for a single simple recipe, which I give to the students and walk through once. They can study it on their own to work the math if they want to, but this shows exactly what is going on with the math already done (but annotated and visible) so one knows how it works. And then we go to the computer which does all the math (and more) so we can start making conclusions and hypotheses about a recipe. Doing the math by hand only proves pedantry.
  10. Well, maybe it is aluminum somethingelse. Perhaps rather than the precision implied by the word oxide we should use the undefined words tarnish or corrosion? Googling tarnish and aluminum tarnish leads to a lot of commentary about alkaline detergents causing darkening of aluminum cookware (sometimes the explanations involve atomic hydrogen too). Sounds like fluxes for clay to me. (Queue the trumpets for the entrance of Nerd to tell us about Na vs. K in clay bodies...). But exactly what is the black residue - oxide, sulfide, hydride (did I just make up a new chemical word) - ? But back the hantremmer's original question, I think we are all in agreement that it has no consequence to the clay/ceramic outcome. Or at least many of us have seen the black goo and suffered no consequence from it. Just part of the deal here. dw
  11. My considered opinion on the practical side without submitting my dirty sponges to an analytic house for spectroscopy: The wheelhead is probably not pure aluminum, rather is an alloy of some sort? Never tried rubbing my wheels (including those of the school and community centers, various brands and ages) with sandpaper to examine the abraded content, only that which happens naturally through use. Plastic wheelheads (ClayBoss) don't do it, nor an ancient steel one, only aluminum alloy wheelheads. If one leaves clay debris (esp. porcelain, where is Nerd when we need him to explain the chemistry behind it ) on the wheelhead, it will discolor. (Same thing as aluminum barrels on pugmills vs. porcelain.) Then you can "polish" it shiny again with a bit of white clay and water as a fine abrasive, but the abraded slurry will be black on the sponge or your hand. If the clay is brown/dark, it will still happen but you just won't see it as clearly as black on white. If you polish it long enough with intermittent clean sponge squeeze-outs, it will stop coming up black, suggesting whatever black oxidation has now been removed. The same will happen if you don't use the wheel for a long time, the surface of the aluminum will oxidize very slightly, perhaps imperceptibly when looking at the dry wheelhead, but the black slurry will come up as soon as you hit it with the white clay/water/sponge. As for color, yes the ceramic grade alumina oxide or hydrate is a white powder. But aluminum oxide sandpaper/grind stones/etc. are not white. And black is just concentrated gray, perhaps made to appear blacker than gray by the water? And so I stand by my opinion that it is abraded oxidized detritus from the aluminum wheelhead, and of no significant consequence to the ceramic ware in process.
  12. The black stuff is a slight amount of aluminum oxide that abrades off the aluminum allow wheelhead when you rub it with clay on your hands or sponge. It happens with all clay, but is more visible with white clay or porcelain. Aluminum oxide is one of the standard oxides in clay and glaze, so there is no adverse reaction that will occur if it is left on your sponge or clay. Even though it is black in color, the color will disappear when fired. There is not enough aluminum oxide involved to materially change the chemistry of the clay or any glaze on top of it. If your sponge has a lot of clay on it, squeeze it out in the reclaim bucket, no problem. If you still get some residual black on your sponge during the final wipedown of your clean wheel, rinse in the sink drain.
  13. confused over earthenware and glazes

    With stoneware, the typical bisque vs. glaze temperatures are bisque low (often the same as earthenware) and glaze higher. With earthenware, it is often reversed. Bisque a little higher to solidfy the ceramic and glaze lower. Just use the appropriate cones for each stage.
  14. Firing An Accidentally Glazed Green Ware Pot?

    Joseph, a question about your holds. It seems logical to me to have the 30 minutes at 550F as that's a bit above ignition for many organics and this would encourage/improve burnout - or maybe you have a different reason. But I'm coming up blank in my little head what might be happening for an hour at 1600F?
  15. Minspar

    As Min indicates, Kona F4, a soda spar that is now obsolete and unavailable, is reasonably close to Minspar200 and can be substituted with little or no change in the fired glaze. However, just for clarification, back in the day Kona also produced a potash spar labeled A3. Check your recipe and confirm that it was F4 or A3.