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Dick White

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  1. One thing I will add to the discussion about flocculating and deflocculating a slip (or glaze) is the chemical reactions are reversible. If you mistakenly over-flocculate, you can just add some deflocculant to thin it out again, and vice versa. In your case of wanting a thickened decorative slip, the issue is complicated by shrinkage on drying. A slip that has been flocculated to thicken it so it stands up on the surface of the vessel still has the same clay-to-water balance, and will shrink and crack as it dries. It is better to create a slip that has more clay in the same amount of water. The problem is that you can't put enough clay into the same amount of plain water to accomplish this as it becomes too thick as mud to stir. You then deflocculate the slip and it instantly turns runny, and now you can add more dry clay. You must add dry clay, not more slip. You are trying to raise the amount of clay in the existing water, and adding more slip adds more water at the same time as it adds clay. So, as Callie suggests, take some dried greenware made from that same clay, crush it to powder (inside a doubled plastic bag to control the dust) and add it to the developing slip until it finally is the thickness you want. Be sure to sieve it to get all the lumps out.
  2. This is not responsive to your question in the second paragraph, but about the causal issue you refer to in the first paragraph. If you put some green or blue food coloring in the wax resist, you will be able to see exactly where it has been applied. Don't use other colors as they are hard to see against some clay bodies.
  3. Check your connections and the continuity of all elements. It is possible for a kiln to reach the 1700℉ range with one element out. But it won't go much past that. Perhaps the connector to one of the elements has come loose or there is some damage to one element. For a quick test of whether all elements are coming on, slip a scrap of paper behind every element, then turn it on to some program, doesn't matter what program, for 5 minutes. Then turn it off and check the paper scraps. Any that are charred are behind working elements, any that are not charred that element did not turn on. Troubleshoot from there.
  4. If your floor sags and wobbles when you walk around on it, then the wheel will wobble when someone else walks by. If your floor is steady when you walk, then the wheel will be fine too. The motor of some wheels has a bit of hum when it runs, and the wood floor may act like a sounding board and the noise will be louder than if on a non-resonant surface.
  5. As a glaze chem instructor, recipe formatting is a dicey subject. Each roll of the dice produces a different answer, depending on who you are, where you came from, and why you are here. So let's cover the basics. The total quantity of materials in a base recipe should always total to 100 or very near to it. That 100 then can be interpreted as 100 percent, or 100 grams, or 100 ounces, pounds, or tons. Each individual material in the recipe will be measured in the same unit of measure, except for percentages as percent is not a discrete unit of quantity. But that's where the notion of 100% becomes useful. No matter what size gross batch you wish to mix, an item that is 27.2% of the 100% total base will always be 27.2% of the gross batch. Now it is just arithmetic to make a small batch, a larger bucketful, or a barrel, and the proportions will always be correct. There are 2 schools of thought on the 100% rule. Some believe the entire recipe, including the colorant oxides, opacifiers, suspension agents, etc. should total 100. After all, it's 100% of the whole recipe, right? Others, including me, believe the 100% should apply only to the fundamental materials (fluxes and glass formers) while the colorants, etc. are additions above the base 100%. This allows one to change the color of a glaze without changing the underlying glass, or easily analyze or compare the content of a several base glazes without needing to recalculate them to a common denominator. Next, you have batch sizes. Many potters consistently mix each of their palette of glazes in a particular batch size based on their studio's needs. Some batches are large, others small. A potter's notebook may show a glaze that is a mainstay of the studio as having a list of materials totaling 8,743 grams while another recipe totals only 954 grams. There are no calculations to be made, just weigh out what the list says. That's what works for that potter's routine, but may not be useful for others. Finally, we must address the presentation order of the materials. Classical methods of using glaze chemistry to construct a glaze recipe typically start with the most complex of the raw materials, usually the feldspars or frits. These bring in the necessary fluxes and the quantities are manipulated to create the desired balance of fluxes. Single-oxide flux materials are also added at this time. Next, the clay materials are added to bring alumina up to the desired level, and finally pure silica is added until the recipe is fully balanced. Listing a recipe in this order demonstrates an intellectually rigorous development of the glaze, and many old-school potters keep doing it that way because that was what they were taught was the proper way to do things. However, that makes mixing the glaze more difficult than it needs to be. Some find it easier to stir the various materials into the water if they are added in order from largest amount to smallest, stirring the bucket after each addition. I find it best to always add the clay materials first so that the beginning slurry is immediately flocculated, and thus subsequent materials do not quickly sink to the bottom and hardpan. Then the rest of the materials in size order, largest amounts first. Thus, my preferred format is probably different than any you might find in other potter's notebooks. You have Mr. Beardsley's books in whatever format he kept them, so you have a choice - you can simply republish them as found (and we must sort it all out), or you can do the recalculations and reformatting to suit some other standard.
  6. I am not familiar with exactly what Skutt might have done to change the standard Bartlett Genesis programming in their version of it, but the stock Genesis has a checkbox to turn "Slow cool" on or off at the end of a standard cone fire. When enabled, it does a 9999 drop to 1900F and then 150F/hr to 1500F. This may not be exactly what is in M^6G, but it is close enough. Check if your Skutt device has that same checkbox.
  7. It is common that DC motors are harder to spin one way vs. the other, the Shimpo Whispers are the only ones I'm familiar with that are totally free spinning when not on. It sounds like you'll need to do some electrical diagnosis to determine if there is a controller fault or cable fault and there is no power reaching the motor, or if there is power reaching the motor, then the motor is faulty.
  8. Could you get a science department lab coat and modify the lower part of the back so that when you leave the bottom several buttons open, the long coat functions like a split leg apron but now with sleeves?
  9. Can you loosen the belt tension (and possibly take the belt partially off) so that the motor can run free? What happens now? Does the motor spin up (and change speed with the pedal)? If the motor spins up with no tension on it, then the problem is later in the drive train. If the motor hums but doesn't spin up (even with a little twist to get it started), then it's a motor problem. If the motor doesn't even hum a bit, its a controller problem.
  10. Not trying to defend the kiln manufacturers, but if they felt obliged to put 60A plugs on their power cords (which in turn would oblige us to put a 14-60 receptacle on the wall), now we are all at 4 wire configurations. Given the basic price of a kiln (and for the user, the price of the installation), another wire shouldn't be a deal killer. But then I don't own a kiln company. I just fix them.
  11. interesting discussion, Bill, always learning something new from you. Regarding the continuous draw, a manual kiln on high will be a continuous 48A draw, so the circuit needs to have 60A capacity. Even with digital controls, the relays will cycle, but I doubt an exactly-sized wire (8ga copper for 50A) inside the wall will cool enough between the 10-second cycles to mitigate the overheating. I've heard of this 125% rule not only for kilns and similar high demand heating devices, but for commercial lighting, e.g., a shopping center store with the entire ceiling of light fixtures on one circuit. Add up all the fixtures and wire/fuse it at 125% because that circuit is full-on all day and half the night. The kilns are manufactured with 50A cords and 6/50 plugs (consistent with the 48A rating), but the whole idea behind NEMA plug design is you can't plug together incompatible amps or voltage. So the manufacturer's 6-50 plug won't go into the higher rated 14-60 receptacle even though the circuit before it must be wired/fused at 60A. And of course, when we get into kilns bigger than 50A (single phase), the 125% rule pushes us to something more than 60A service, and there are no plugs/receptacles above 60A, thus direct wire is the only option. Regarding the Skutt chart, it only specs the receptacle and minimum wire gauge, no reference is made to fusing. Both the L&L and Paragon sites show specs of seemingly mismatched 6-50 receptacle and 60A breaker/6ga wire. And that design factor you looked up for home duplex outlets needing full 20A internal capacity despite the 5-15 face explains why all the ("modern") kitchens and bathrooms I've lived in had 12ga wire and standard 5-15 outlets. Never saw one with a T-slot that could take a 5-20 plug. And on the other hand, our brand new school studio has nothing but 5-20 duplex outlets - there are a lot of them and I'm pretty sure each of the 15 wheels (for which there is a separate outlet for each) does not have a separate breaker in the utility closet (which we, appropriately, can't get into to check). Could very well be solely because of the difference between commercial vs. residential codes/practice. cheers on this rainy day here.
  12. Denice and Bill, the notion of needing consistent rated ampacity of everything in the circuit (i.e., 60A breaker requires a 60A receptacle, or the 6-50 plug on the kiln should not be fused higher than a 50A breaker) is incorrect. The code is not about protecting the end device (that's UL's job), but about protecting the wiring from overheating and catching fire inside the wall. For example, bathroom and kitchen circuits are required to be 20A, but the receptacles are all ordinary 5-15s. The issue with kilns and other constant draw devices that leads to the 125% rule has to do with heat dissipation of the wire. There are no perfect conductors in general commerce, so all conventional wires generate some heat as current passes. Larger wire generates less heat for the same amount of current, and if a current is intermittent as in most situations, the wire can cool between uses. The engineers who wrote the code determined the maximum ampacity that can be carried by any particular wire gauge (and in a particular installation type, e.g., open air, enclosed raceway, conduit) in normal usage without overheating. However, if a particular circuit is intended for an end device that will draw full ampacity constantly (as when the kiln is running at full heat for the last several hours of the firing), the circuit must be upsized to 125% of the device rating so that the circuit won't overheat as there won't be any intermittent cooling time. Circuit breakers protect not only from the overcurrent surge of a short circuit, but also from overheating due to a long draw of a lesser current. The largest plug-in kilns are typically are 48A or so with 6-50 (or 15-50 3-phase) plugs, but the servicing circuit must be rated for 60A for the heat dissipation. (And if the circuit is longer than 50' from the panel, the wire gauge should be upsized to account for voltage drop, but the breaker need not be increased.) Thus, the 6-50 receptacle on the 60A circuit is ok, and the 50A breaker (even with heavier wire) on the kiln circuit is not ok.
  13. The wax will make the alumina powder stay on the surfaces you paint it on until you can put it in the kiln. Then the wax will burn up, but the alumina powder will still be there. With water or just the powder, it might fall off as there is nothing to make it stick.
  14. The float is an imperative - for both of us. You don't want to lose your chamois in the throwing slurry, and I don't want to have to take the pugmill apart to pull out your lost chamois, or just as bad, find your chamois in reclaim as I am throwing. Another easy float is a common fishing bobber. A small one is enough. Poke a tiny hole using your needle tool in the end of the strip of chamois, and put the spring-loaded line clamping wire hook through the hole.
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