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Dick White

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  1. There is some conflicting information about the first firing floating around, both from different kiln manufacturers, for different purposes, and even within the same manufacturer's instructions. L&L's printed manual has long instructed owners of their new kiln to do an initial break-in firing of the empty kiln (but with the furniture) slow bisque to cone 5 (yes, five, not oh-five) with a 3 hour preheat for the dual purpose of seasoning the elements to develop a protective oxide coating and to set the cement used during manufacturing to hold the kiln bricks together. Their newest manual indicates these instructions are for both the Dynatrol and Genesis controllers. Conventional wisdom by some other kiln manufacturers instruct owners of their new kilns to do the initial firing slow to 04. This is consistent with the recommendation from the manufacturer of the Kanthal elements for seasoning newly installed replacement elements, again to develop a protective oxide coating on the wire. Out on the interwebs, many commenters who own these other brands of kiln will adamantly (but incorrectly) assert that new owners of all brands of kilns should do the initial firing to 04. And now we have this new video from L&L for programming the first firing on a Genesis controller that instructs a glaze firing to 04 with a 1 hour preheat. However, if one looks around on the L&L website, there is another video for programming the older Dynatrol controller for the first firing that is consistent with the printed instructions, i.e., slow bisque to 5. Is the basic kiln constructed differently for a Genesis vs. Dynatrol controller that it would need a different initial firing? I don't work there, so don't take my word for it, but the conflict seems fishy to me. With 3 instruction sources to choose from (the printed manual and 2 videos), I would go with the 2 that are consistent, i.e, the printed manual and the Dynatrol video. But maybe that's just because I am a recovering accountant...
  2. DigitalFire can tell you about the usage of most of those. https://digitalfire.com/material/list
  3. Ok, now download the firing log and feed that sweet thang into @jay_klay_studio's graphing program to visually see the tracks of the 3 sections. And if you really want to have some fun, add another 9999 drop all the way down to 100 after your regularly programmed cool to log how looooonnnggggg it takes for the last several hundred degrees. Several times over the years I've printed the extended graph of a few kilns as a teachable moment for the students of the virtue of patience, i.e., "Can I get my piece tomorrow?" "No, next Friday."
  4. For the brush hair, you can go to a full line fishing store and get squirrel tail and deer tail used to tie fishing fly lures.
  5. The reason most studios are picky about not allowing outside clay is because of the risks involved in the glaze firing. Earthenware bodies or glazes mistakenly put in a mid-fire glaze firing will create a terrible mess. "But the label on the box had a number 6 in the cone rating. Oh, the zero in front of the 6 was meaningful? How was I supposed to know that." (Yes, I have had that very conversation with students.) The other side of the issue is just about all bisque traditions are similar no matter the intention of the body in the final glaze firing. So, bisque firing a low-fire raku clay to cone 06-04 is no different than bisque firing a cone 5-6 clay to the same 06-04, or even a cone 10 clay bisqued to the same 06-04. My guess is if you respectfully talk with the studio management about your opportunity for the raku firing and ask them to bisque fire this non-standard body, hopefully they will understand there is no risk and accommodate your special request.
  6. @Bill Kielb alludes to an important aspect of a kiln vent - make up air. For whatever air is being exhausted, there must be an equal amount coming back into the room. The challenge for a kiln vent, is that make up air must come from a different direction from the exhaust. If the location of the make up air, such as another open window or door in the room, is too close to the exhaust vent, the stinky air will just be sucked right back in through that opening. The make up source needs to be around the corner from the exhaust so that the stinkies dissipate in a different direction and the make up air is clean.
  7. The Bartlett and Orton controllers have an algorithm (designed by Orton, licensed to Bartlett, so both have it) built into the cone-fire mode that senses actual heating rate (which may or may not be what was programmed) and adjusts the final temperature for the intended cone bend. As @Bill Kielb notes, the Orton tables focus on the last 100C/200F, and the published cone-fire firing schedules for Bartlett controllers all start the final segment at 250F below target temperature regardless of cone or rate. In my kilns which are all performing well, the Genesis logs show this happening as programmed; the final ramp at medium speed is a straight line at 120F per hour. What I do not know is, if the kiln were faltering in the final segment, does the controller average the achieved rate over the segment, or adjust incrementally as the segment progresses. In some of my diagnostic work with others' failing kilns, the rate of increase may be reasonable at the beginning of the final segment, but slows down significantly by the end of the segment (i.e., the graphed temperature is a curve, not a straight line) so how does it calculate the appropriate end point? What does this mean for your programming? I don't know, just throwing it out there that many potters think that if the controller finished without an error code, their kiln is in good shape, when it is not. The controller is working around the kiln failure. You'd like to mimic that, which is awesome.
  8. Do not replace the 50 amp breaker with the required 60 amp breaker unless the wire is 6 ga. or better.
  9. When defloculating with sodium silicate, a funny thing happens if you go too far. It begins to thicken rather than get even thinner as you would expect. And you add more and it gets worse. Solving the problem requires understanding how defloculation occurs. The clay particles are sensitive to the acidity or alkalinity of the water. If the glaze slurry is too loose and separating quickly, a small dose of an acid, such as epsom salts or vinegar will flocculate it. If the glaze slurry is too thick, a small dose of an alkaline, such as sodium silicate or soda ash, will deflocculate it. But, as mentioned, if you deflocculate with too much sodium silicate, it starts gelling. Because the underlying problem is too much alkalinity, you just need to neutralize it with some acid. It seems crazy to flocculate this glaze that has gotten too thick from over defloculation, but that is what you need to do. Scoop out some and try it with a few drops of saturated epsom salts solution or vinegar. p.s., in your recipe, did you mean manganese dioxide instead of magnesium dioxide?
  10. As I see it, there is a lot of good work establishing ground zero for the perfect glossy durable midfire glaze - flux ratio of 30:70, Si and Al molar within limits, Si:Al ratio around 7-8, boron molar within limits, etc. Yes, perfect, but boring glazes. Mayco Stroke and Coat, a solid performer from 06 to 6. In my glaze chem classes, I tell them to consider theoretical perfection, but also realize there is are a lot of more interesting effects to be found outside of ground zero. Some of it may not be durable, though some may be just fine, do your tests. I have to this point stayed away from subjective experience with this particular recipe, but one of the reasons it is so popular in my community studio is because of the interest it creates. When layered with certain others of the studio glazes, we put the Amaco drizzles to shame. It is a solid glaze by itself, or Amaco/Mayco Flux in the same bucket. Why? In my studies of glazes, it is the high boron in this one when layered with other lower boron (conventional theoretic levels) glazes. Higher boron levels create a borosilicate glass. Lower boron levels create an alumino-silica glass (not quite soda-lime bottle glass, but the chemistry is moving in that direction). Layered borosilicate glass and alumino-silica glass do not mix to a homogeneous blend, but rather they are immiscible and flow through each other in rivulets or create a faux-oilspot effect. Now I have the student's attention (and if they are not careful, a kiln shelf to clean). As DuPont said 90 years ago, better living through modern chemistry.
  11. And back to arguing about the Katz documents - all those graphs are based on a flux ratio of 30:70 R20:RO. Stull ran his infamous chart on this flux ratio. There is wide agreement that this ratio is optimal. There is also modest agreement about silica and alumina molar limits of generally 2.5 to 5 for silica and .25 to .5 for alumina for mid fire with a Si:Al ratio of around 7 or 8 being a nice glossy glaze. There is less published documentation showing that when keeping the flux and Si:Al ratios constant, cone 10 melt occurs higher up the diagonal on the Stull chart and cone 04 melt occurs lower down the diagonal. There is also wide agreement that boron is helpful at mid-fire and necessary at low-fire, with the Katz diagram showing recommended molar levels across the range of temperatures. But when we mix all that together and do something different, we don't really have any guidance, so as @davidh4976 just said, we talk past each other. The recipe @GEP is asking about is completely outside of conventional limits . The flux ratio is 22:78 - Katz spoke of not going above 35:65, but nothing about going below, where this one is significantly below the gold standard. The Si:Al ratio is 7.8, nice for a glossy, but the molar levels of 4.1 and .52 are in the cone 10 range. The boron molar level is at .72, a bit high for cone 04 (i.e., off the Katz chart). So what we have is a high calcium semi-matte (based on the flux ratio) with cone 10 glass (based on the silica and alumina molar levels) and cone 08 boron molar levels that comes out a nice glossy cone 6. As @Bill Kielb said, "there are an infinite number of fired combinations to which research could be applied."
  12. @Min et al, I just pulled the tile after 24 hours half submerged in 30%* cleaning vinegar. There is no change in gloss or color (we use this glaze with a bit of copper and some tin/zirco for a nice turquoise). I will go shopping to find some plain lye (Drano brand has other stuff in it) - when home-brew testing, I like to hit the sample tile with something stronger than kitchen cabinet chems (since I run my dishwasher so infrequently, it would be next year before I would complete the Katz-recommended 30 cycles...). *Grocery store vinegar is diluted to an acidity of 5% - sometimes. In recent years as manufacturers everywhere try to reduce costs by invisibly reducing quantity in the same package, some grocery vinegars are now 4%. That might not make any difference in your oil and vinegar salad dressing, but if you like to make your own pickles, you need to check the label and make sure you are getting a 5% vinegar. And there, I did it again, took the pottery discussion in another direction. Now we can share recipes for pickles...
  13. Mea, this is a interesting recipe that shows up in a variety of places. The version you have is very close to one that we have been using in the Audrey Moore/Wakefield (Ffx County Parks) studio since forever. That one is Gerstley 50, EPK 17.5, Silica 32.5 (our Gerstley vs. your 3134, about the same effect; your EPK and silica are reversed from ours). From a chemistry standpoint, the massive amount of Gerstley or 3134 generates so much boron that it could/should be a low-fire glaze - and indeed I have seen it in published collections of earthenware glazes. At the same time, the alumina and silica levels are quite high, and so the glaze is robust enough to survive at cone 6. With the demise of Gerstley, I am reformulating it to use 3134, and my revised recipe becomes similar to yours. Something to consider - 30 EPK is a lot to have in a recipe, and will cause issues with shrinkage and cracking (leading to crawling during the firing) so replace half of it with calcined EPK. It just so happens right now I have a test tile with my revised recipe soaking in vinegar, so I will come back in a day or so with the outcome of that.
  14. Agree with @Bill Kielb about the possible worn breaker. Note that element resistance and watts/amps are inversely proportional. Worn elements with higher resistance pull lower amps (and generate less heat, hence the drawn out firing times until it just can't finish), so when you replace them, the amperage pulled suddenly increases again to kiln spec. And just as suddenly, a worn breaker begins causing trouble. Breakers are specific to the particular brand and type of the panel, usually not interchangeable with any universal substitute, so you will have to look around to find that Siemens brand and type breaker, perhaps even needing to go to an electric supply house instead of the usual orange or blue big boxes.
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