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Bill Kielb

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Everything posted by Bill Kielb

  1. Sorry, Just saw this post but I believe negatives are 90, so 9010. A copy of an old Bartlett manual below. You can get a fresh one from the Bartlett control site if necessary.
  2. You may have to take up some slack elsewhere so judiciously anywhere you heat it red hot it will bend like butter. Some of those areas look to be out so much that if you collapsed them right at that point all the coils would then be touching. Try and find locations that are stretched a little excessively and you should be able to gain som room in these other other areas to help you put these back in without coils touching the adjacent coil. Your elements are very likely flexible enough that you can gingerly remove a foot or two to work on. Ultimately you will need enough room to shrink the sections back in with the torch. You can try heating areas of the elements that are stretched a bit more while in the channel and often these areas will shrink when you do this providing room for you to then heat the crawled areas and place them in more easily. Patience and good luck! I once put a kiln back together where nearly all the elements had crawled out nearly everywhere. It took time, but it ended up pretty perfect and is still firing today.
  3. I would put them back in with a torch regardless, you are stuck. The key is to not compress them so much that the coils touch. You have only fired them once so they still should be reasonably flexible and you may be able to remove and judiciously shrink them until you can neatly get them back in. This is odd that they moved out this much so hopefully they were cut to the right length to begin with and are the right elements. Next time maybe corner pins if you are going to replace with the same. Since this is L&L with their element channels, Neil may have seen this and have an idea.
  4. Sounds reasonable. Just to check the thermocouple is all the way in touching the end of the protection tube. Given all that, I would say offset. There are other considerations with respect to how your controller was set up, one being the relay switching speed and the other being the priority of how the zone control determines when to consider a segment finished. And still other things you could confirm such as actual operating voltage etc.... Factory specs on all this would be my next suggestion just to check and confirm they have not been altered but it sounds like you are ready to dial in offsets as the next logical step to even things out. Others may have thoughts and Neil sells these things so maybe he will weigh in.
  5. Before commenting, I would like to know the total time your kiln took for each firing. Most kilns are marginally powered so as their capacity decreases the firing times increase. At some point, usually when the elements degrade by 10% or so (150- 200 firings give or take) the kiln will have more difficulty in making exact cone temps. Why? Well in the last 250 degrees of the firing the kiln needs to go about 100 degrees per hour for the cone to bend where expected. If it can’t do this because of capacity loss then it struggles to make the cones bend appropriately. The slow glaze program I believe should have completed in 7 hours and 37 minutes. How far away were you from this timeframe? Finally to answer your question you can put in an offset in to compensate but at some point if a wear issue your kiln will likely be inconsistent from bisque to glaze and when worn enough will eventually give you a rate error. The question becomes, how worn are your elements? If not at all, then dial in your offsets to get your kiln calibrated. I looked this up and it appears to have protection tubes over the thermocouples so there are already thermocouple offsets built in. Don’t know them by heart, but they are important and your thermocouple placement in the tube is also important. Any chance any maintenance has been done prior to the kiln beginning to over fire?
  6. I suspect the Barium may have soured the popularity of the frit. Who knows though often pottery is such a small client to the frit industry. Lots of clears out there, didn’t bother to map this out in any glaze software but 7% clay says it likely settles hence the bentonite.
  7. F 524 appears as a strontium barium frit so hard to substitute. 3124 is similar in silica, boron, and alumina with more calcium instead of strontium and barium. search Glazy for a chem analysis
  8. Maybe, got a bunch of test tiles I have done many ways that led to our fix for what we saw. I am pretty happy with what has worked for over a year now so hopefully it will be useful for someone. I suspect there are a variety of cause and effects. More research, better for everyone. For us it demonstrably repeated itself when applied very thickly so getting it to occur over and over especially on test tiles (green, bisque, rebisque after application) was easy. It will be interesting to see what you find. The implication that it could induce crawling is most interesting to me.
  9. Every time I spray, the least absorbent part of the pot is where the underglaze is. Where the bare pot absorbs and drys quickly I need to wait for the areas with underglaze to dry. The areas that dry slower pool, drip, run much more so than the areas that absorb the glaze quickly. In effect it can end up effectively thicker while drying on a more impervious area. This is super obvious while spraying as runs and drips become a concern. So maybe potential for more uneven coating of glaze if you will. Assuming the layer takes longer to dry rather than be partially absorbed it is likely more predisposed to crawling. I believe @Roberta12 makes a great point.
  10. Excellent catch.! Underglaze definitely clogs things up so your glaze will end up sort of thicker in those areas and therefore enhance the potential for micro cracks as it drys. If your overglaze does not possess the healing power necessary then crawling likely. If you ever spray glazes this becomes an obvious difference as the underglaze areas tend to pool and not absorb so we are allowing a considerable amount of extra time for those areas to dry. So thinner underglaze is always less troublesome than thicker.
  11. We noticed that in many of our tests but after looking at the vertical surfaces, no movement so we changed our thought that the area was too refractory or not melted.. Tests with various matte clears revealed these areas when melted would go from matte to glossy where the thickest underglaze was and of course often color / brand dependent. That was a reasonable indication that for that local area the silica was raised enough to move from (5:1 ish towards 7:1ish) matte to gloss. Some folks actually counted on this happening for the effect. Anyway, almost all these issues went away after upping the boron until a clean melt was achieved. Adding high boron fritt to the underglaze seemed to back up the theory as well. We did experience a reasonable limit though especially with the true matte clears.There is only so much you can make them melt without destroying the matte as well as causing plenty of other issues. Our limit ended up to be: it had to melt well over a drop or splatter of the underglaze which actually ends up quite thick. In the end for us it was easiest to develop a matte and gloss that worked every time over moderate underglaze.
  12. Could be, just have tried many bisque and green samples and from that experience bisque had no effect, before and after. In our case bisque only sintered the thick underglaze which remained refractory in the thick areas when fired.
  13. We have had that happen green and bisque, so from many tests it appeared to be thickness as the main cause and definitely more predominate with certain colors.
  14. We had this problem and it was color specific as well as the heaviness of the underglaze. All colors worked fine as a light wash but as their thickness increased the area above appeared to became more refractory and would not melt. We reformulated our glaze with additional boron to melt and ended up with a decent compromise with how thick certain colors could be applied. We then developed a gloss clear and matte clear that worked in this fashion The picture below is the result. Although there is heavy black over orange, the matte glaze appears fully melted. In the past the heavy areas of coverage would not fully melt, even the random dots of yellow splatter would struggle to melt. This works for the clear as well, just don’t have a picture handy. We confirmed this with a number of test tiles before settling on the final recipe’s. Let me know if you want the recipe’s to try, message me. No guarantees but they work for us on our porcelain.
  15. Makes sense, lower the pressure above the clay only helps remove entrained air. Must work, race proven. In the video it appears to stay in a slight vacuum right up until he opens the hopper to refill. Appears the outer dial is inches and inner is bar. His machine appears to achieve approximately 27" - 28" which is quite significant actually.
  16. Must require some vacuum else manufactures likely would not add a pump, right? Must not be too much, at 28” hg, water boils at 90F. Could double as a freeze dryer at some point. LOL
  17. In the end it’s all about what vacuum can you achieve over as much clay as possible and for how long . So long as you can achieve enough to suitably deaerate, it doesn’t matter how you seal it. It would be helpful to quantify this though as it would be a good measure of pump performance. What does the gauge say you can maintain?
  18. To just add, often called underglaze techniques and come in forms such as liquid and pencil that can be applied in many ways including layering and feathering, decals, scrafito, etc..... so lots of examples on the Internet combining all these things. Some simple pics below of painting (Brush apply) with them, and maybe some outlining with glaze pencil and clear glazed over.
  19. As I recall it is the high temperature deviation and comes factory set at 100 degrees. I believe it is the amount that the kiln can exceed the setpoint until an alarm is generated. Setting is something between 18 degrees and 200 degrees from memory. Check your sentry manual and it will detail. Since your kiln is operating I would just check what alarm setting sensitivity is currently entered in for htde. 18 would be your most sensitive amount and 200 degrees the least sensitive.
  20. Plastic deformation and temperature related strain? I almost don’t know you anymore! LOL. Slumping?
  21. Good to know. Just curious looking at the Scarva site, is this is a cone 10/11 clay for full vitrification?
  22. I would stick with your normal practice for your glaze and some porcelains can stick to the shelves, not all but some. Kiln wash shelves for sure and grog under or you could paint your foot with alumina wax for insurance.
  23. Works for me. Porcelain is still clay that some find a little different to throw but is generally smooth, no grog, fairly white so glazes can be a bit bleached compared to other clays. It can slump more than other clays when fired depending upon the shape and for that reason folks avoid stilting and can stick to the shelf given the right clay and circumstances. As far as bisque, 04 your regular schedule should be fine, ventilation in the bisque as normal. Glaze fire as you normally would as well. Not sure why the top peep is open in the glaze fire, if you have a counterflow exhaust run as you normally would for bisque and glaze. If you have an automatic control then slow glaze in cone fire mode is about 10-12 hrs in bisque and 8 hours in glaze. our porcelains and glazes work just fine in fast glaze actually. What have you heard that concerns you?
  24. I see your cuts and do not see any air bubbles In the first picture but see many in your wedged sample. Where did the cut slabs come from? Do the cut slabs fire Porous?
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