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Dick White

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Posts posted by Dick White

  1. 8 minutes ago, Theresa Buckner said:

    Does anyone know if you can fire a piece of ceramics that I primed with GESSO?

    I have not tried that specifically, but my general knowledge of ceramic glazes is that would not work. The raw glaze needs to adhere to the surface of the ceramic body, and if there is anything in between, such as dirt, dust, oily residue from fingers, stray wax from the bottom, etc., the glaze will shrink back from that dirty spot as it melts. I would think the gesso will do the same.

  2. You have the basics from the UToobs. As for timing, I set the bottom switch only on low for as long as the ware is still damp. This warms it up from below. You can test the humidity coming out of the kiln by holding a small mirror or piece of glass by an open peep hole and any invisible steam coming out will condense on the colder glass. When no more humidity is coming out, you can start the bisque firing by turning all switches to low for an hour, then twist them all up to medium for an hour or so, and then up to high for the remainder of the firing. Be aware that the kiln sitter is designed as a safety cutoff device only. Good protocol uses witness cones on a shelf visible through a peep, and manually turn the kiln off when the appropriate cone is down. Some folks rely on the sitter to turn it off at the right time, but that requires careful calibration of the sitter for accuracy, and even then it can be off depending on the load.

  3. Those are what are known as infinite switches. Unlike switches that click to a specific position, e.g., on/off like a sideways light switch, or a rotary off/lo/med/high switch, these switches are akin to a dimmer that can be set anywhere (an infinite number of positions) from off through full on. When the pointer is at low, it turns the elements on for a short time (a few seconds) and then off for a longer period. When the pointer is closer to high, the elements are on for a longer time and then off for a shorter time. The numbers 0 through 100 are not exactly the percentage of time that the elements are on, but they are indicative of the relative range of off most of the time to on most of the time. At 100/high, it probably will be on continuously. Each of those switches controls one set of elements inside the kiln, so you have to turn them up in tandem for the kiln to heat evenly. At the same time, if you find that a particular area of the kiln tends to run hotter or cooler, you can change where you set the dial for that area to adjust the heat input.

  4. Direct copy and paste from the Mason Color Works FAQ:

    WHEN I USE BLACK STAINS TO MAKE GREY SHADES THEY TURN GREEN/BROWN/BLUE/PINK ETC. WHY ARE THEY NOT SIMPLY GRAY?

    Do not use black stains to make gray shades by using small amounts in the glaze. Blacks are made of combinations of cobalt, iron, nickel, chromium, manganese, etc. If low percentages are used, the resulting color is often that of the predominant oxide in any particular black pigment. Care should be taken to use the correct glaze chemistry to avoid combinations that create color problems. It is better to use the gray pigments that we offer.

  5. The FireRight top knob is an early version of automating the ramp up in temperature. The numbers on the dial approximate the number of hours it will use ramping up from cold to full heat, so you don't have to go back every hour and turn up another regular switch. I'm not exactly sure what the bottom knob does or why it should be set to a particular number. Need to know the make and model, as Bill suggests, to find a manual for it. I have recollection of an old kiln that used the second knob to set a final power level dependent on what is being fired. The kiln sitter, of course, is a final shutoff.

  6. If you are in a commercial location with only 208v available, the kiln rated for 240v will be about 15% underpowered, and thus will probably reach only bisque/low-fire earthenware temperatures. Mid-fire cone 6 is highly unlikely. The switches and controls will still work. What is not working are the elements. If you replace the elements with ones that are designed to give the full temperature from 208v, then you should be able to get cone 6 from it.

  7. I have fiddled with mica some, using it in sodium silicate stretched/crackle forms, and then a modified very low temperature (cone 018ish) raku-like firing to put in the smoke bin to carbonize the crackles. The issue is that the fun colored mica products are for cosmetics and soap (bath bombs) and they either melt out at hotter than ~1400F or the color burns out. There are a few types of mica used in ceramic bodies that hold their own at the higher temps, but you have to order them specially and they don't have the fun colors.

  8. 25 minutes ago, Bill Kielb said:

    one exception: I had an engineer / potter present the argument that they did not want to exceed 400 degrees because that was still below the ignition temperature of most paper and textiles. Who could argue against that? I reminded her to remove all flammables including the lawn mower gasoline can from the shed where they kept the kiln. She laughed and said good idea!
     

    :rolleyes: Perhaps she had neverboiled water for tea on the stove and watched the steam come out of the spout of the kettle. It's not the paper burning, it's the water exploding.

  9. On 9/2/2020 at 1:02 PM, Benzine said:

    Neil, does this work with any of the old digital controllers?  I have a JD236 in my classroom, and have been interested in getting a controller that would allow me to monitor the kiln via an app.

    Just an FYI,  for the phone app to work, you need to have wifi internet available at the kiln. The controller communicates via the internet to a cloud server maintained by Bartlett, and the phone app logs into that same server to read the data. You may already have wifi in your classroom, but if your school doesn't have it, then you'll have to work with the IT department to get it.

  10. 7 hours ago, Hulk said:

    Any road, if spod is a feldspar, is Petalite also?

     

    Yes, petalite is classed as a feldspar. Petalite is more often used in clay bodies than glaze, so that's why I didn't include it in my comments about feldspars in glazes. But you can use it if you have it. As for the foaming/washing issue with spodumene, a soap is used during the crushing and processing of the ore, and traces of it remain on the final product. When mixed with water in the glaze slurry, it will generate its own miniature bubble bath, which can cause problems as the glaze dries on the ware leaving bubble voids which become pits in the fired glaze. The soap can be eliminated by washing the spod first in a bucket of water and then drying it. I find that a messy process. An alternative is calcine it to 5-600℉/~300℃ to burn off the soap. I keep tubs of calcined EPK, ZnO, and spod on hand for use as needed.

  11. The sitter bar is not "bent nicely." In a properly calibrated sitter, the bar or mini-cone is bent to a 90° angle for the claw on the outside to release the drop plate. Yours is bent less, so it released early. Hence the hard cone 5 not yet cone 6 result. If you don't have one, get a calibration disk and adjust the sitter claw and drop plate. There are uToob videos how to do that.

    dw

  12. Kona F4 was (again, "was" is the important word) a soda feldspar mined in Spruce Pine, NC. A bit before the turn of the century, there was an unfortunate fire in the mine, and it was uneconomical to repair and reopen. End of Kona F4. There was another company mining a soda feldspar on the other side of the same mountain. That was named NC-4. For whatever marketing reasons, the company selling NC-4 decided to change the name to Minspar. So, if you ever run out of that historic bag of Kona F-4, Minspar is almost the same. In some areas of the world, the feldspars are typically not sold by brand name, but by generic type. Soda feldspar, F4, NC-4, Minspar, all about the same and mostly interchangeable with each other (after testing to be sure exactly how whatever you just got works in that particular recipe).

    Potash feldspar is the flip side of soda. Feldspars typically have both sodium and potassium in the percentage analysis, and whichever of them is higher gets the name attribution.  Potash spar is the generic term for spars that have more potassium than sodium. Custer, G200, G200HP, G200EU, and Mahavir are US brand names for spars that lean to the potash side in varying proportions. If your Custer is fairly old, it is similar to the G200 and I would just mix the small amount of G200 with the Custer and not worry about it.

    In the interest of completeness, but not really part of this specific question, spodumene is a feldspar that has lithium among its alkaline fluxes. If you need lithium and can't pay the current highway robbery for it, try recalculating your recipe to use spodumene. And finally, there is nepheline syenite. From the geologist's perspective, it is not a true feldspar, but is close enough to be called feldspathic. Names, schmanes, whatever. It is a flux material very high in sodium, higher than proper soda feldspars.

    carry on as you were,

    dw

  13. We had this very discussion a few weeks ago with a different person who had a new-to-them Paragon kiln with a similar issue that the controller limit was set lower than the rating of the kiln, and thus made the kiln unusable at its full rated temperature when the controller cut out too low. The user manuals from Paragon all claimed this could only be adjusted at the factory, but @Bill Kielb found an instruction page that indicates how to get into the special options menu of the controller and fix this. Below is the page he found.

     

    B12C3555-B0C6-47DC-AFEC-0426145EA919.png

  14. This is a question for the knowledgeable electrical engineers in the audience. I am trying to remotely help an acquaintance far across the pond who is having trouble with her kiln taking too long and tossing E1 errors. There are no proper kiln technicians in her area, so she must rely on a local sparky to do the necessary maintenance and repairs. We have been tossing ideas back and forth, including information reported to her by the sparky. One issue is her house appears to be suffering some voltage drop, but a review of the log of a full power test shows a severely lagging ramp of between 30 and 40℉/hour above 2000℉. That tells me the elements are shot. She claims they are only a year old and not many firings, but then she dropped a comment that sent me scratching my head. The sparky, seeing that the resistance of the elements was increasing (a sign of decreased amps/watts being pulled) and "corrected" that by shortening the elements until the resistance went down to original spec. I am thinking a serious WTF was he doing, but please, one of you who really knows what you are doing, am I nuts or is the local sparky nuts? I understand the Ohm's Law calculation, but my less-than-complete understanding of kanthal elements is that the amount of heat radiated is a function of the surface area of the wire. As the wire oxidizes and wears over usage, the diameter of the wire decreases, thus decreasing the surface area, and consequently the heat radiated. The measured increase in resistance, thence transferred through the Ohm's Law calculation to watts of power, is merely a proxy by which we can estimate the degradation of the heating power of the elements, and shortening the element to decrease its resistance is doubly counterproductive to heating the kiln. Please help me help her. Thanks!!!

    dw

  15. 17 hours ago, Bill Kielb said:

    I believe G200 Is being replaced by G200 HP which is slightly different but still worth trying IMO these are all so close that some simple glaze calc ...

    Some history and clarification about the G200 series feldspars - G200 was (the important word: "was") a potash spar roughly equivalent to Custer at the time it was in production. The G200 mine in Monticello, GA began to run out in the early 2000s, but they were able to keep the brand going by using a feldspar from another mine in Siloam, GA (about 50 miles distant). That feldspar, however, was considerably higher in its potassium content. They resolved the chemistry by trucking a soda feldspar in from Spruce Pine, NC (about 250 miles distant, probably from a mine near the Minspar source and the now-closed Kona F4 source mines) and blending it 70:30 Siloam potash spar:Spruce Pine soda spar. In about 2009, the company decided it was getting too expensive to truck both feldspars for processing and blending in Monticello, so they announce to their customer base that henceforth they would sell only Siloam product with the higher potassium, now labeled as G200HP. They revealed that they had been blending it for years and customers could either blend it themselves with Minspar or recalculate their glazes to the higher potassium content of the G200HP.  Lauguna, for example, began mixing them in their own facility and selling it as "Old Blend." However, as happens in the world of mined products, the Siloam mine ran out in about 2013, and G200HP is now unavailable. To meet the demand for a potash spar, they began to import a potash feldspar from Spain that was comparable to the original G200, and labeled it as G200EU. This product remains currently available, but not as widely carried by distributors and a bit more expensive due to the transport costs from Spain.

    At the same time, Laguna found a potash spar in India that is very similar to the original (and blended) G200 and imports it under the name Mahavir feldspar.

    Shifting now to the Custer issue, the original G200 and the blended G200 were roughly equivalent at the time, and often subbed 1 for 1 for each other in glaze recipes with no problem. When potters began to realize the bag of G200 they had so blithely just picked up from their distributor was in fact G200HP (the bag and label coloring were similar, only the printed name with the additional letters "HP" was the give-away) and their glazes were overfluxing, some did their own blending but then changed to using Custer. But then people who had long been using Custer began to notice their glazes were underfiring. After some potters sent their Custer out for testing at independent labs, it was found that the Custer product was now actually significantly lower in potassium and alumina and higher in silica than advertised. Pacer Corp, the producer of Custer, still claims in its technical literature that the analysis is basically the same as advertised some 20 years ago and blames the problem on customer (the potters) misuse. In my experience and similarly reported by others, if you have an old recipe containing a significant amount of Custer (40%+), you might need to recalculate your recipe, or change to G200EU or Mahavir.

  16. 1. Get a 5 gallon bucket for each bag you want to reclaim (or just a few buckets and work through the clay a few at a time).

    2. Open a bag and pour one or two cups of water into the bag around the dry block of clay.

    3. Put the bag in the bucket. I like to leave the top open for now.

    4. Start filling the bucket with water. As the water rises in the bucket, it will expel the air from the bag.

    5. When the water in the bucket reaches just above the level of the top of the block of clay, seal the bag with a twisty wire or rubber band. There will be only a little bit of air left in the bag.

    6. Add some more water in the bucket to cover the bag of clay.

    7. Wait a few days. The pressure of the water in the bucket pressing on the side of the bag which is pressing on the  water that was poured into the bag will force that water back into the block of clay.

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