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saltcreekstudio

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  1. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Thank you so much glazenerd. I see now. I will need to slow my bisque firing (a lot) and allow for more oxygen in the chamber by proper loading and not stacking tiles. I have always used the factory preset cone fire programs, largely due to being ignorant of heat work and what actually happens to clay in the kiln, and because my results were good. In 2017 you wrote, "I can tell you that´╗┐ ramping between 108-125F an hour from 1200 to 1750F, while supplying lots of oxygen inside the chamber will resolve most all of these issues." What about the 0-1200F range? And getting from 1750 to 1938F? The factory preset slow cone fire program takes 12.5 hours, but in the 1200-1750F range it ramps up too fast (from what I can tell on the skimpy graph in my kiln manual). What ^04 program can I follow from start to finish? I can manually program my kiln with up to 32 segments.
  2. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    A 12 hour bisque?! Yowza.
  3. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Ok, I will. By "test tiles" I meant starting from scratch, making new tiles to test theories. I'll be sure not to stack and will double check my venting. I'll program the kiln to run a slow firing schedule for the bisque and see what happens. I like the idea of the soak at 1650 if need be. Thanks for that.
  4. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Thank you for your suggestions and info...I'm learning a lot here and have a long way to go. I'm beginning to think harder on switching to a lighter colored body. Having achieved nearly perfect results with the Vashon Red w/ grog (VRG), then to have it all go pear shaped is beyond frustrating. It sounds like it's just the nature of this finicky clay and it's components. I suppose I'll try a few tests to see if I can get more carbon burn-out in the ^04 bisque firing, and see what I can learn in the ^5 glaze firing tests too. Thanks again.
  5. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    When you ask if I've carefully checked to verify uniform oxidizing atmosphere throughout the kiln... you mean by testing samples? Not yet, but I'm going to. I assumed my vent was working fine because I checked it with a lighter flame (it was being pulled into the holes in the lid after I turned the vent on). Maybe something with the vent is amiss despite that. Thanks for suggesting the detailed list idea... I will do that before I do my test firing. I appreciate the "root cause" perspective. Thanks.
  6. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Glazenerd, an anyone else who knows about carbon coring, check out this picture: I believe I'm seeing carbon coring?
  7. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Ha, I wish the answer was as easy as "Oh, I've just been firing low-fire clay as a mid-fire!" I have not broken up the tiles to look inside. Carbon coring is not something I know about.
  8. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Yes, I use the self supporting witness cones throughout the kiln. I've always bisque fired to ^04, then glaze fire to ^5. In a thread above, I added pics of the way my tiles used to turn out (see the pine cone tile) and the way they often turn out (the sea turtle tile). And many come out of the kiln a variety of shades in between.
  9. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Yes, on the same shelf. I think the darkest clay outcome is from those that that are fired at the hottest parts of the kiln. I will do a test firing and load the kiln in such a way that addresses all the responses/questions. I stopped loading wares on the top an bottom parts of the kiln b/c it seemed to be underfiring more than a cone, but will load test tiles in those areas for the test fire.
  10. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Hey there. No, Vashon Red w/ Grog is a ^04-^6 clay. I've achieved perfect, bright and vibrant glaze results (see pic of pine cone tile above) with a ^5 medium speed firing when my kiln will was purchased, but terrible results (see sea turtle tile next to pine cone tile) not long after. Your info is really interesting and I need to digest it a bit more. I find that I keep thinking, "aha! that's it!" but then remember that I've proven the theory incorrect over this past year with trial and error. I plan to do another test firing, a really tedious one, to share and maybe whittle down some of the mystery. Thank you so much! **edit... I think the longer, medium speed firing is giving me darker, worse glaze results.
  11. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    It's been happening for at least a year. I've wondered about whether or not something in the mining area was different. Maybe that's it. Still weird though that some tiles turn out really brown, and others less so, even from the same batch.
  12. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Yeah, it's never been an issue for me before, but now he opposite is happening. The color of bisque doesn't vary, but the ^5 firing (glazed or not) is way too dark.
  13. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    Hey Mark. That's the truth! Minus the "fun" part. Ha! This conundrum has been driving me nuts. I've been using the same glaze for years. I've had the same kiln model (only bought a brand new version a couple years ago, not long before this all started going wonky. The clay has changed from Highwater in NC to SPS, but I've achieved excellent results with the SPS clay initially. I can't remember that far back, but maybe I got good results because I didn't double stack that load for the bisque. I only stack in twos. I'm guessing that still could be causing the problem (that the bottom tile in the stack is being deprived of air)? I'm going to test it. Thank you. ***edit*** except that I've had the top tile in a double-stack turn out that dark brown color. So confusing.
  14. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    HMMMM..... I like what you are saying here! So maybe the reason that clay color is varying is due to the stacking at the bisque fire, and that the bottom tile is not getting as much airflow. Oh, but I'm pretty sure I've doubled stacked and not had this issue. It's been long enough now that perhaps I'm not remembering correctly and I was only putting one tile down. I will definitely test this theory. It seems like the only reason that some tiles are so much darker (the ones possibly not getting enough air on the bottom). I don't see a difference in the clay color after firing to 04 bisque, but all the bisqued tiles are jumbled up in preparation for the glaze firing, and I don't know what's what. I'll find out. I've held a lighter up to the downdraft holes in the kiln lid to make sure the vent is drawing air, and it is, but maybe I'll double check my ducting and the spot it connects to the kiln floor, too. Thanks, Maria ***edit*** except when I fire the unglazed tiles there were very dark tiles both as the top tile and bottom tile in the stack. Ugh.
  15. saltcreekstudio

    Mystery firing problem. Not for the faint of heart.

    I hear you on the "more than one thing going on with the kiln" thing. The elements are brand new and aren't worn out yet. I will definitely give my wiring connections a look. Thanks. The clay body thing is what I want to believe too, but it's not adding up. I'm having dark and lighter color even from the same bag of clay, in the same firing. And I really don't think it's glaze thickness. The glaze seems the same consistency it always has been, and I'm brushing the same way I have for years. And, the clear difference is that darkened clay... I should mention that occasionally I'll place a different kind of clay (white stoneware) on the higher shelves b/c that particular clay is tolerant. Floor is an inch from bottom.
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