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Bill Kielb

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Everything posted by Bill Kielb

  1. If it helps we found color and thickness to be a primary cause. In our case we needed a tested glaze that worked pretty much no matter how the artist wanted to paint it else be accused of stifling creativity! Hence the glaze solution. I think I only increased the boron a few points, so .15 to .19ish. Marcias matte is on glazy if you want to double check what it was brought up to. Anyway, IF this is your issue folks have been successful at adding a tiny amount of boron fritt or GB to their underglaze colors prone to this. Tiny amount seems to be key else the glaze chem locally is a mystery. Hope that helps. As usual tesssssst.
  2. Same relay, so that is good, right form. The actual moveable contact on the new one has overheated without a sign of the terminal overheating which means either it was defective from the factory and misaligned or lots of load went through it. I would double check the wiring and element resistance as wired to be sure that 25 A or more continuous wasn’t going through it. If not, then it likely came misaligned and overheated during firing. IME it’s rare to see them melted without the melting occurring right at the connection first. The moveable contact on this one looks annealed. Definitely worth thorough check IMO before dropping a new one in.
  3. I suggest Double check your element resistance, the relay rating, relay wiring diagram as it could be a defective one but it really is hard and very unusual to melt one that way. Reminds me of double pole relays I saw earlier this year that were the wrong form. That relay ended up as form Z but looked identical to form C https://community.ceramicartsdaily.org/topic/25213-duncan-kiln-not-reaching-temperature/?do=findComment&comment=203748
  4. If a flame is coming out of the pilot assembly some way then that often indicates the orifice or pilot deflector / mixing tube is blocked or partially blocked. The thought here is the reference to vent is the pilot primary air location where air should go in, so if true then maybe some blockage in the pilot deflector / mixing tube and not the orifice. Remove and clean the assembly, often spiders like to nest in the deflector tube. Gently clean everything, do not enlarge the pilot orifice, maybe pass a tiny needle gently through the hole if blocked or blow it out backwards opposite to the typical flow. If you post a picture, this can be confirmed with a bit more confidence. A weak flame will not keep the gas valve engaged. The pilot flame should be reasonably strong and blue and engulf the thermocouple. Wispy and yellow generally will not work consistently.
  5. If my suggestion of using 1 tablespoon of underglaze seems to be wasteful then by all means scale it down. Yeah, thinking about this a little further, if they are using 2oz bottles then a tablespoon is probably a bit much for a test sample as that is a 1/4 of their stuff and UG is likely expensive for them. I see lots of folks with 2oz bottles for variety in color and pints for base colors they use. Actually just running this in my head with the tablespoon of underglaze assuming about 65% is raw materials with a likely percentage of 20% or more clay already in the formula, this probably kicks the clay up another 20% or more using the teaspoon of epk so maybe scale this all back considerably as well to start the test.
  6. If one is able to modify their glaze then testing as we did for color and thickness toleration is fairly easy especially with a boron based cone six glaze. In the end we had a tolerant glaze and the ease of testing led to being able to test whole panels of thickness, color, and manufacture easily, hundreds actually including combinations of thickness and color while minimizing the amount of underglaze used. If unable, there was the practice by some of adding a bit of Fritt to the underglaze and maybe not consuming a bunch of underglaze to get it to work. Gerstley and epk contain silica, alumina and flux, Gerstley not so much on the alumina, ……………… so maybe a good indicator, maybe not.
  7. Maybe. I can tell you what the testing revealed. Simple tests, where a light coat of underglaze is connected to a very thick coat of underglaze and the overglaze bubbles in the heavy area and stays smooth in the light area. Follow that with a better glaze melt (increased boron slightly) and all of a sudden the glaze begins to finish smoothly in the heavy areas. This proved true for matte and gloss overglazes btw. We share those results so folks can consider the result. I have learned though that there is often speculative disagreement and contention over this to which I try and phrase things as ………consider this possibility……. Simple to do your own test. The tests we did indicated something counterintuitive and helped us solve our problem.
  8. This would indicate that the coefficient of expansion of the fired clay and fired glaze are not close enough or compatible enough and delayed crazing will likely occur in items using this clay and glaze. It generally means adjust the glaze chemistry for a better fit or in the case of a commercial glaze use a different or more compatible one. Most mechanical or other solutions such as glaze thickness alleged will not really fix this and the combination will eventually craze. Most folks would consider this not suitable for food products and this would be a glaze defect when used with this claybody. Food and bacteria will accumulate in these cracks and the cup will be weaker than a non crazed equal. There are folks that consider crazing to be aesthetic and ok to use though. Most potters out of conservative caution will not sell crazed products for potential food use. Here is a good read IMO on glaze defects. The safety issues are summed up in paragraph seven. https://digitalfire.com/glossary/crazing
  9. Makes sense, it was not offered to complicate things it was offered as a diagnostic not presented in the other threads. If that is the issue, then there are other remedies than formulating your own glaze. We worked on this for over a year before concluding it was the central issue. Had someone pointed out the possibility it would have saved us a year of testing. Along with all the typical remedies everyone was speculating on at that time.
  10. What strikes me is this is going to be a very personal decision perhaps even influenced by the upcoming winter weather. There may be no perfect answer and trying both out might be a way to narrow this down or even deciding one is better during the winter than the other. As far as learning, always super nice to get instruction but also with all the content on the web a nice opportunity to learn on your own. So the pandemic is bad, but web learning opportunities have never been better and ……. People do become masters of their trade, craft, art by practice, application and study. Instruction is great but even with instruction practice is the only way to mastery. Maybe schedule the most travel convenient for the winter months and in the summer you can join the other. Both experiences likely will be beneficial and you get to choose when. As far as overwhelming knowledge, from my perspective, in clay there are many components to learn but learning step by step is really how humans progress. I enjoy learning and after over half a century it truly is what I enjoy most. A very wise person once told me when I was in my teens and was mad at myself for not accomplishing something fast enough muttering under my breath in disgust ……. He said “be careful how you treat yourself” that has stuck with me since and now when I look back I am pretty satisfied with all that I have learned and, excited about what I might get to learn tomorrow. For me I just need to add effort to my latest interest and pursue opportunities as I find them available. Not all work out perfect but over time they all seem to add nicely to a growing knowledge base. I wish you best of luck on your journey!
  11. There could be a lot of reasons for this but …….. the wheel circuitry has its own fuse so a short in the wheel likely would blow the onboard fuse and no longer trip any GFCI or breaker. The machine would no longer do anything no matter where plugged in. The other possibility is a damaged cord, cord grip, water has seeped into the unit and is tripping the ground fault. This is only a possibility but I would thoroughly examine the plug, cord,, cord grip and where it enters the wheel. If it’s tripping breakers then the short might be reasonably obvious. If it’s tripping ground faults then anything wet or even stains from having been wet can trip a GFCI.
  12. Something to consider: I do see bumps and we have seen this with many underglazes when applied thickly, usually uniform coverage thick. So the possibility to consider is the areas where underglazes are applied thickly can become refractory and the over glaze simply does not melt In these areas. After testing for over a year we found thickness as well as certain colors were more refractory. The end result was to formulate a clear gloss and matte that would melt better over these areas so the artists were free to create as they preferred with underglaze. It’s fairly easy to test for this condition and wash style painting rarely bubbles and is much more porous and less refractory than the heavy areas. So if all the wash areas are fine and many of the heavy application areas bubble, this is likely your issue. To make matters more confusing When underglaze is applied solid it also affects the amount of glaze that can be applied over it. Heavily underglazed areas will close off the pores in the bisque which will then take longer for the overglaze in that area to dry which means if double dipping, wait until the underglazed areas dry, they will take longer than the rest of the pot. Dip too soon and you likely remove as much overglaze as you put on. A thinner than normal layer of overglaze definitely makes the bubble condition more likely. Easy to test if this is your issue though.
  13. Here is a mix percentage for various rutiles you may have use for in the future - no significant chrome. https://glazy.org/materials/15393 It takes roughly 2.12 parts more Magnesium carbonate to equal 1 part Magnesium Oxide. Magnesium Dioxide is not a typical glaze chemical so I assume you intended to use Magnesium Oxide. So in your example above you would need approximately 3 g MgCO3 X 2.12 = 6.36 grams of Mag Carb (MgCO3) to equal 3 grams of Mag Oxide (MgO).. Magnesium carbonate does off gas or lose a great deal of its weight (Over half) when heated so it can cause other difficulties in some compositions. Here are some sample chrome tin recipes that may give you ideas when looking at their chrome and tin composition: https://glazy.org/recipes/77052 https://glazy.org/recipes/32817 https://glazy.org/recipes/79136 The last recipe has some nice line blend info to show the variations in color vs different alumina levels for that recipe. Chrome tin recipes can be a bit of a challenge. See below line blend. Cobalt glaze: Mauve / Pink / Lilac here https://glazy.org/recipes/5542 Careful with cobalt oxide and carbonate, same issue. You need just under. 1.5 times more Cobalt carbonate to equal 1 part oxide.
  14. I would suggest reading the article in the link below start to finish, it addresses most of your questions. If after reading, you may have some new questions to post. Lusters need ventilation in application and during firing. Lusters fire around cone 018 so not very hot compared to your normal glaze firing. Lusters generally can be fired very quickly. The fired luster is influenced by the glaze it is fired on. Too thin an application will not end up shiny and gold. Too thick can drip. Much of this knowledge is obtained by experience so in the beginning maybe some test pieces before applying it to your best work. Here is a good article that is a nice overview IMO. https://ceramicartsnetwork.org/daily/pottery-making-techniques/ceramic-glazing-techniques/use-ceramic-luster-glaze/
  15. Turning it on low and leaving the kiln open may keep it below boiling, depends on the kiln and surroundings. Preheating it and then letting it sit overnight works for some folks as well and uses less electric. In the end it’s whatever works best for you and allows you to heat up the pots gently over enough time for them to dry. Automatic kiln controls allow you to set a preheat cycle where the pots are heated slowly to about 180 degrees and held there precisely. Using that method often it’s easy to say 1,2 or 3 hours is enough time. Other methods are usually figured out over time, so experience is a thing. The basic idea is heat them (gradually) some temperature less than boiling and they will dry reasonably fast with no risk of shattering later because of steam.
  16. Just asking, is this a recipe that was obtained somewhere? I ask because Titanium appears in the base recipe and again later as a colorant as Rutile which is predominately Titanium dioxide. So I am wondering if there is a mistake in the composition originally or as posted before dropping this into a glaze calculator.
  17. Pre planned randomness seems like failure to me and a nightmare for traditional QA/QC. It will be interesting to see how long this lasts.
  18. It might work, but often when a glaze does not heal from fired surface tension issues it’s the peak temperature that is the culprit so until the glaze cools and the surface tension changes enough it won’t heal itself. My observation: some glazes perform better at cone 5 than 6 so cone 5 with a fifteen minute hold keeps the peak temperature down and still fires to cone 6 heatwork. Or for stubborn glazes a drop and hold is easiest to get this done. It’s so counterintuitive that it often takes a bunch of frustrating testing. You are ahead of the curve as you have already discovered a successful method. The last 200f of the firing is where most of the melting or maturity happens (eutectic: where there is finally enough energy to get the flux, silica and alumina to melt) and if following the Orton cone chart middle column 108 degrees per hour should get cone 6 to drop at 2232 f.. rates over the last 200 degrees of the firing are very important to achieve predictable heatwork.
  19. Good to see your timer actually goes from 0 to 20 Yes it will be trial and error based upon when you turn the firing knob ( not the timer) from low to high and dependent on how fully your kiln is loaded.. As Neil mentioned other manuals might give some insight. As a general rule for most ordinary pottery glaze firings tend to go 7-9 hours and average 300-450 degrees per hour rate. For bisque fires 10-12 hours at an average rate of 200 degrees per hour. How long you bisque has a great impact on ensuring removal of all the organics. Drying things off and removing liquid water usually is a very slow warming over 1, 2, 3 hours as needed or warm up the kiln to 180 degrees, turn off and let it sit overnight. Some strategy to warm up but not make it to boiling point so things dry gently and slowly. No steam. As far as firing speed, manual kiln operators often after dry do something like: turn to low for two hours, medium 2 hours, then high until off. Low medium and high being relative to the kiln, load size,and experience which might mean turn to dial indicated 1 for two hours, then 3 for two hours, then high or 10 and let it make temp. You will need to experiment and learn, but your general goal is to be 7-9 hours for glaze and 10-12 hours for bisque …….. eventually with experience it will be whatever has proven to give you the best looking results for your glazes, clay, throwing and artistic preference.
  20. The timer is simply a countdown timer from ten hours to zero and is a backup fail safe device to make sure the kiln shuts off. Traditionally it is set for a small amount of time greater than the expected firing time. So if one expects the firing to end at 7 hours then the timer is set at seven hours thirty minutes. Now for the hard part, one needs to learn a little bit about firing schedules and controlling their kiln, assuming it has manual controls. What type of. Firing controls does it have? This may help, although not the best explanation it should give you an idea. https://youtu.be/_K_Glhstc4Q
  21. Seems right to me, It may be effective at much lower amounts if you continue testing. 12.5% at this point seems to be a new maximum needed. Nice work! The use of sugar as a retarder in concrete is generally up to .06% by weight BTW. At roughly over .08% it starts to become an accelerant.
  22. Whatever you get crimp it very tight. Single levers like these are fine but don’t give you the leverage of compound. My version of tight is likely different than yours as I am regularly tested at 110 lbs grip strength which is quite high ………. for other reasons. When I single lever crimp, I squeeze as tight as I can for a decent period of time. Ratchets won’t release until they have been squeezed enough, again they are a bit more goof proof, but single levers are fine as well. Squeeze tight.
  23. If you are handy with a torch you can heat up and unwind some element to extend your pigtail, (It needs to be glowing red, so careful!) but really they ought to be doubled over or folded back on themselves at the end and this will reduce the length of the element ever so slightly so ONLY a temporary fix even done well. Neil is correct, get some decent crimpers. A decent crimp takes lots of force and crimps so tightly that it will not burn off. You can find crimpers at big box stores but Amazon does have some very economical ratchet style (even Klein tools) that won’t release until enough pressure has been applied. A bit more goof proof.
  24. Never a good sign if the plug begins to warm, especially very warm. Usually indicates the plug / receptacle connection is wearing or the wiring to the plug is undersized or a connection is beginning to fail or the wiring to the receptacle is undersized or a bad connection. In other words, there is a reason that the wires are getting very warm which definitely deserves attention to make sure all connections are good, wire size is appropriate and any circuit protection device is sized correctly to protect the circuit and ultimately against the risk of a fire.
  25. Most pottery suppliers carry commercial glazes as well as there own. Google is your friend in this case, there are several for sure and they likely carry the major commercially made glazes such as Amaco, Mayco, Duncan, spectrum……. You really should determine what cone you want to work at, and have a reason why which will make you learn the pluses and minuses of their use. Scarva website https://www.scarva.com/en/us/Home.aspx
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