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dom92

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  1. Unfortunately I don't have any photos of unglazed handles. I'll try to do that the next one I make. I appreciate all the tips everyone. Definitely a few things to consider next time around.
  2. Okay, I understand now. That's good advice. Thank you!
  3. Rockhopper - Interesting theory about the glaze, and your tests definitely show a difference. My kiln is very small and has only one shelf. I'm not able to use cones because I have no way to view them.
  4. Hello - I've been experiencing some odd warping during glaze firing and I wanted to ask the experts here for assistance. I use a porcelain slip purchased from a well regarded local ceramic supplier (they make and sell their own line of slip). It's labeled as Cone 6 slip and is supposed to be slightly translucent. The label goes on to recommend bisque firing at 1940 F and glaze firing at 2200 F. Everything is fine through bisque firing. Once it cools, I apply a Cone 6 glaze and then fire again to 2200 F. It's after the glaze firing I'm getting the warping: https://drive.google.com/open?id=1SeMLeRahIeQyISG0r7ck3B0Q-3MCiYQX Here's the weird thing. I've made these cups many times before with the exact same slip and I've never experienced this before. The only differences I can pinpoint are that this is a new batch of slip (the exact same type of slip though) I just purchased and I'm also using a new glaze I haven't used before (although I doubt glaze can have anything to do with it). I have a fully manual kiln with no sitter so I basically just slowly ramp it up to temperature over about 8 hours and watch my pyrometer closely for temperature. Is it possible this is just a difference between porcelain slip batches? I suppose my pyrometer could be off as well and I'm simply firing too high and just don't know it? Using cones isn't an option for me currently as my kiln has no viewing window or peep hole. I'm open to suggestions as to what could go going on here.
  5. I'll pick up some cones the next time I'm at the store. Until now I've hesitated on using them because my Skutt kiln has no spy hole. The only way I'd have to check a cone would be to open the kiln, and I like to avoid doing that so I don't cause unneeded stress to the piece I'm firing.
  6. The entire setup is a K2 Instruments model DP-902F. The thermocouple end is just two wires twisted together with a dab of what looks like solder connecting them. The K type thermocouple I ordered to replace it was this: https://www.amazon.com/gp/product/B00XJ0VUBG/ref=od_aui_detailpages00?ie=UTF8&psc=1 A totally encapsulated thermocouple. Definitely different than what I have now.
  7. Okay, everyone, I think I discovered the obvious problem. I was following up on neilestrick's last post and looked at the manual again. I clearly misread things before. The pyrometer itself has a max temperature of 2372 F, but the thermocouple that came with it is only rated to 1500 F. I would presume that trying to fire the thermocouple some 700 degrees above its max rating could cause some readout accuracy issues. I'm an idiot. I've already got a high temp (2372 F rated) thermocouple on order and it'll be here on Saturday. I'll hold off subsequent firings until then. I appreciate everyone's patient replies and advice.
  8. I have no other slip in my possession right now, so there's no way I could have confused it or taken from the wrong container. Here's a photo of the actual label: https://drive.google.com/open?id=1jhW5ELUxn14f38kONTrtvVy80RyG7WB0 I don't have any "program" as my kiln is fully manual with a limitless switch. I discovered one new potential problem since my original post when I pulled out the manual for my kiln today. It notes that the pyrometer is not rated for temperatures above 2000 F and that if kiln temperature is raised above 2000 the pyrometer *may* show an error code until temperature drops below 2000. My pyrometer went up to 2232 F just fine, but now that I know that's above its rated temp I'm wondering if what I was seeing was completely inaccurate? I'm also wondering if this was as simple as not stirring up the slip well enough before pouring. Sometimes I'm not as diligent with that as I should be.
  9. Unfortunately all of my other bisque from the same slip has already been glazed. I'm measuring temperature by using the electronic pyrometer that came with my kiln.
  10. I didn't have any actual cones in the kiln. After this I recognize I need to pick some up next time I'm at the ceramics store. I'm wondering about the kiln overfiring as well, like perhaps the pyrometer malfunctioned. It didn't seem to be porous after bisque firing. I put some water in the cup for awhile to check for leaks or seepage and there didn't appear to be any.
  11. It's hard to say because it melted in to such a messy blob. The parts that were still identifiable did appear to have glazed just fine. There's no chance I used the wrong slip in this case. One other possibility I was just thinking of. Could this could occur if I didn't stir/mix the liquid slip enough before casting?
  12. I had an odd failure happen yesterday, and I'm not exactly sure what to make of it. I had used a premixed ^6 porcelain slip to cast a small coffee cup in a plaster mold. The label on the slip container states: Glaze fire at Cone 6 - 2232 F Bisque fire at Cone 04 - 1940 F The kiln I used was manual, so I slowly (over about 8 hours) brought the piece up to 1940 F and held it for about 15 minutes, then let it cool on its own in the kiln over the next 12 hours. Everything seemed successful. I then applied some Cone 6 glaze and then, over several hours, brought the kiln up to 2232 F. When I opened up the kiln the next morning I was shocked to find my cup a melted blob on the floor of the kiln. It was like it turned to lava sometime during glaze firing and just completely collapsed. What's odd is this failure came at the end of successfully making 3 other cups using the precise same steps and the same slip. I'm of course hesitant to try to make any others until I figure out what happened here. I'm thinking of several possibilities: - My pyrometer is off and I didn't actually get it up to proper bisque temperature - Bisque temperature was fine but I didn't hold it long enough - Ramped it up too fast during glaze firing (I have an electronic sitter but haven't hooked it up yet) - A problem with the slip itself (which I think is unlikely since it's from a well known local manufacturer and since I've had 3 previously successful firing/glazing) And of course there could be something more simple I'm missing here. I'm open to any suggestions.
  13. Thanks, Fred! I should have guessed that there was a special mix out there. I'll give it a try!
  14. Do the experts here have any sage advice on the best plaster materials to use for making a good slip casting mold? Until now I've used a wide variety of commercially produced slip casting molds and they've all been excellent in quality and construction. Nice rounded edges and very durable. I've even dropped a few here and there and all they did was leave a dent in my vinyl floor. Anyway, this weekend I wanted to take a shot at making my own slip casting mold using plain old plaster of paris bought from the local hardware store. It "works," but I can already tell this won't hold up for long. One drop, even to countertop level, and it'll probably explode in to a dozen pieces. I'm thinking this primarily due to the type of plaster I used to make it. Do the commercially produced molds use a different kind of plaster? I do have a bag of jewelry casting investment (which is primarily POP), and I was thinking of giving that a try as I know from experience how smooth and durable it is. I just don't know if it will absorb water from slip properly.
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