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F Crow

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Everything posted by F Crow

  1. That's very interesting to hear as so often soaks are mentioned in firing schedules I've come across. No harm in trying it though, so will give a go at firing to 1200oC without the soak in a firing soon too.
  2. Hi Bill, I added the soak with the thought that it would insure that the entire chamber had reached 1200oC. Feared that without it some pieces (perhaps towards the bottom of the kiln) may be slightly underfired as the temperature range of the clay is 1200oC-1290oC. I do intend on firing without a soak as you recommended when firing to 1220oC though as this shouldn't be an issue. Hope my logic isn't too flawed in this thought...
  3. UPDATE Tried a firing of; -150oC/h to 1000oC -60oC/h to 1200oC -15min soak Had a good result with the dark glaze. The surface still isn't completely smooth, but a massive improvement! Unfortunately there was no difference with the light blue glaze though. I actually bought a new batch and tested both the new and existing glaze in case the one I had was contaminated, but both turned out the same... Riddled with pits! Will try another firing soon and go to 1220oC to see what happens there. If that doesn't help then the manufactures have asked to send them some bisqueware to test the glaze themselves. Have also emailed Nabertherm about updating the controller so awaiting their response.
  4. I am not sure either to be honest. Would guess that maybe it is the programming of the controllers that differ and allow for more programmes and more segments... But again, I know almost nothing about electronics. There is a USB port in the controller that allows programmes to be created externally on computer and imported, so maybe I could upgrade the controller from a B400 to C440 via that port... I will actually email Nabertherm and find out if that is a possibility. Nothing ventured nothing gained! Thanks again for the help.
  5. Yeah if ever changing kiln in the future I will be more diligent and research into the controller like you, not just the size and amperage as I did with this one... Not sure if ny controller can actually be changed upon further examination. However I know very little about electrics. Thinking that if this is the case, it may be why the upgraded controller cannot be bought separately though.
  6. Apologies for the slow response, busy few days. Know very little about electrics, but having looked at my controller now perhaps it actually cannot be changed and that is why they won't sell the upgrade unless with a kiln as it must be made together...
  7. I have a Nabertherm top 80 kiln with a Nabertherm B400 controller. Wish I could upgrade to the C440 controller as this allows up to 10 saved programmes with up to 20 segments in each, but it doesn't seem that it can be purchased without buying a kiln at the same time...
  8. Thank you so much for the informative response. Definitely seems to be more variety in approaches to firings out there than inconsistencies. Makes it a hard field to navigate and figure out! The manufacturers actually ran a test of their own with one of the troublesome glazes using a firing schedule of; -500oC/h to 1030oC -75oC/h to 1200oC -15min soak And they claim to have had no issue... However they didn't recommend going as fast as they did in the initial segment. So I will definitely give a go with a faster first segment leading into a slower rate at the end of 60oC/h for the last 2 hours. Putting a bisque on today so will be a few days before I get to try it out.
  9. Thanks again for the advice, it is very appreciated! Wish I had learned these things when studying ceramics, but from reading around online it seems tutors skipping over theory about firings etc isn't uncommon practice. Try to learn as much as possible reading various sources but there are so many variables in the world of ceramics it's hard to weed out what is relevent/reliable and what is not. All my work is hand built, either slabs or press molds, and never thicker than 6mm (or approximately 1/4inch) and I leave ware at least a day after glazing to dry out before packing into the kiln, so hopefully a faster first segment shouldn't cause any harm.
  10. It is a similar thought I was having when contemplating dipping the pieces in water. Among other things I make bowls using a press mold and they are very fine (maybe 3mm thick when fired), so even after dipping them in the glaze they can sometimes take a while to dry depending on the glaze consistency. I too have it in mind as a firing issue which is why I started this thread with a kiln question. Have been trying to come up with potential causes for weeks now and tried so many things (even bought a dehumidifier for the studio!) and the only varient that seems to cause any difference is the firing schedule.
  11. Sorry if I came across as dismissive, I was just trying to understand the reasoning behind your advice. There is so much to learn in ceramics and I certainly admit to having big gaps in my knowledge. It's just not a suggestion I've never seen elsewhere.
  12. Thanks for the advice, definitely seems that what is available to me in Ireland has more limitations than in the US from reading online. Would picking a mid speed segment going up initially be a good option maybe? Something like; - 100oC/h to 1100oC - 60oC/h to 1200oC - drop to 1145oC -20min hold
  13. Sorry I'm not sure I understand what the benefit of dipping the bisque in water would be? I have seen that wiping with a damp sponge will remove potential dust and help the glaze adhere to the bisque as water attracts water. Not sure what the advantage therefore would be in dipping it entirely in water? Could this not just waterlogged and saturate the ware making it difficult for it to receive an adequate glaze layer?
  14. Thanks for the suggestion however this is where my controller only allowing 4 segments becomes an issue. When inputting a schedule like this it would be (at least) 5 segments. 1-60oC/h to 120oC 2-180oC/h to 1100oC 3-60oC/h to 1200oC 4-9999oC/h to 1145oC 5-20min hold This is why I've had problem coming up with a schedule as it seems I'd have to either go fast at first, to slow at top, drop, then soak, or else go slow at first, faster than desired at top, drop, then soak. Obviously neither option is great....
  15. Thanks again for your reply. The glaze is meant to be glossy alright. I have had success with it in the past, but thinking of it now that was on smaller pieces with texture so that may have hidden the defect? None of my glazes move beyond the glaze line (with the exception of one crystalline glaze but I think that is to be somewhat expected) as I use them slightly thinner than recommended. Unfortunately I don't know the composition of the glaze as it is commercially bought. This isn't the only glaze I've been having this problem with however. I'll attach a photo here of another piece with a different glaze showing the same issue. Yes from what I've read a drop and soak schedule does sound like a potential solution! I found a cone 6 schedule on digitalfire but it contained too many segments for my controller so I had to edit it. It did help somewhat but ultimately didn't eradicate the issue. Would you know of a drop and soak schedule that would be worth a try that contains no more than 4 segments, around cone 5 1/2 or 6 temp?
  16. Sorry I didn't explain, this is actually the same piece as the one pictured previously above. Here is the underside in the light showing the pitting issue again.
  17. I can appreciate why you might think that the glaze application is thick based on the photo, but I actually use it thinner than recommended by the manufacturer. Any thinner than applied in the pictured piece and this glaze turns out an awful brown colour... Funnily enough the manufacturer actually suggested trying a thicker application! Needless to say this didn't resolve the problem... Here is a photo of the underside of the piece showing that the glaze isn't thick and standing out from the clay (hope that makes sense...)
  18. I haven't done this but have tried using a damp sponge to wipe down the bisque pieces before glazing. Unfortunately no joy with it though
  19. Thanks for the advice. The glazes I use are actually reactive glazes. What I do is pour off excess water and then add some back in depending on the desired consistency. This allows me to achieve a range of finishes using the same glaze. However having said this, the manufacturer says to use 800ml per 1kg of glaze and then adjust as desired and I use 1litre per 1kg when mixing the glazes. With this, I don't expect that glaze thickness is the cause of the issue.
  20. Brilliant thanks so much will give that schedule a go next firing. I actually prefer the results of the glazes at the lower end of their firing range as they are more vibrant, I think they're called reactive glazes? They are the same glazes I used in school when learning and we all had work that was blue, white, or brown because they all ended one of those colours when fired to 1250oC. It's through my own experimenting with the firing range that I've achieved a much wider colour range.
  21. Thank you so much. It is similar advice to that given by Neil so will definitely try a more extended slow ramp at the end of my next firing.
  22. I use a white ball clay based stoneware clay with 5% grog and a firing range of 1200oC - 1290oC.
  23. Hi Neil, Everything I've read online, from places like digitalfire, lakeside pottery, and even in an article on this website seems to suggest a soak to burn off whatever may be causing the pitting? That's why I've been using the soaks at top temp, or after a drop, to try remedy the issue. My go to book, "the ceramics bible" by Louisa Taylor suggested to soak the bisque longer which is why I've tried soaking it for 45min lately. Unfortunately that doesn't seem to be the solution either though. Yeah I never fire less than 1200. The manufacturer did recommend this as a possible solution but I wouldn't do it for the very reason of under firing the clay. Would you suggest a schedule something like this instead? - 80oC/h to 600oC -120oC/h to 1100oC - 60oC/h to 1220oC Thanks
  24. Oh I thought it was 60oC for the last hour not 100oC, thanks for that. Will definitely give it a try! Here are some images showing the defect I'm talking about. One of the piece looking okay from afar, one of the piece tilted in the light highlighting the problem, and a third of the glaze taken using a macrolens. See how the defect doesnt seem to penetrate down to the clay body which is why I call it pitting as opposed to pinholing.
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