JoLinDesigns Posted July 19, 2014 Report Share Posted July 19, 2014 Can anyone tell me why these broke during 04 firing? 4 out of 6 broke. Are these cooling breaks? I used paragons schedule that they have on you tube. But during the cooling phase the alarm sounded and flashes FTC (failure to cool). I don't understand that since this is what paragon is showing to do. Very confused. Thanks Linda Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 19, 2014 Report Share Posted July 19, 2014 I think we need more information. What is the clay? How were these stacked? How large are they. Were they dry? was it the top tile of each stack that broke?Did you have anything..like grog underneath them or in between them? I am not familiar with the failure to cool alarm? Did the kiln not shut off? Sorry for your loss. Marcia Link to comment Share on other sites More sharing options...
clay lover Posted July 20, 2014 Report Share Posted July 20, 2014 Ditto. , never saw 'failure to cool' ??? Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 Totally dry. 3 weeks + in drying. Cone 5 B Mix Laguna. 12" tiles at 1/2" thickness. I stacked 4 on middle shelf and stacked 2 with 1 bullnose and triangles on top shelf. The 2 on top shelf broke. 2 of 4 broke on the middle shelf (4 stacked). The top one and bottom one broke. The bottom shelf had triangles and small bullnose with no problems. Had nothing underneath nor in between. I was told by Angela Pozo I could stack at least 4 safely. But no more. Hope this helps. Thank you. Firing schedule I programmed: Cone 04 Speed Medium (standard) Preheat 1 hour Hold 10 minutes Cool 200* per hour Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 20, 2014 Report Share Posted July 20, 2014 Four seems like a lot but can't explain the top and bottom cracking. I fire my large slabs on edge. I have done that with small 4x4 tiles as well. Marcia Link to comment Share on other sites More sharing options...
Min Posted July 20, 2014 Report Share Posted July 20, 2014 I don't make tiles but my thoughts would be that firing a 2" total thickness of fine clay tiles on your middle shelf at the preprogrammed med speed with only a 1hr candle is just too fast. Even the 1" thickness might be too much for that fast a firing. Link to comment Share on other sites More sharing options...
Babs Posted July 20, 2014 Report Share Posted July 20, 2014 Top ones too fast temp increase and decrease. Bottom ones shelf a bit rough , tile adhering in places, weight of tiles too much?? Link to comment Share on other sites More sharing options...
clay lover Posted July 20, 2014 Report Share Posted July 20, 2014 in my Skutt, medium is too fast for everything. Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 Oops. Sorry. Looked back at what I wrote down. I did slow speed. Maybe that's why the FTC alarm sounded? If I fire them standing up on edge this large will they not warp? Would I leN them against ghe sides of the kiln? I have another large batch of large tiles to fire. It may be easier/quicker and more foolproof for me to fire single layer then have to go back and wait 3 weeks for drying? Marcia how large are the ones you fired on edge? I do have tile setters. Will those work on tiles this large? Thank you for all of your help! Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 20, 2014 Report Share Posted July 20, 2014 What can you tell us about the ones that did not crack? I have never seen cracks like these ... Smooth and contoured. Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 What can you tell us about the ones that did not crack? I have never seen cracks like these ... Smooth and contoured. They came out perfect. Which is odd because one was the second from bottom and the other was top one of 4 and in middle of kiln. Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 20, 2014 Report Share Posted July 20, 2014 The cracks don't seem to follow any pattern I have seen. They don't look like stress cracks or jagged weight cracks or fast cooling ... Going back to construction ... did you mix together any small bags of leftover clay? Link to comment Share on other sites More sharing options...
Marcia Selsor Posted July 20, 2014 Report Share Posted July 20, 2014 Could you have caused any stress when drawing the patterns? Marcia Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 No no mixing of the clays. Here is my process that I go through step-by-step. I cut the clay right out-of-the-box from Laguna Clay I cut each pug in thirds which is exactly what I need to cut out one tile. I then roll it through my slab roller. II which is also brand new. I might mention too that my kiln is new and only used 3 times...once was the conditioning firing. I started out on one and between two canvases and roll it at 3 inches first. I I turn it and then I roll it at about 2 1/2 inches. I continued do this until I reach the 7/8 inch mark which is where it needs to be 1/2 inch after the final firing. I think carefully place a sheet rock underneath the tile. And then place one on top so that I can remove the canvases. I then just trace my pattern onto the wet clay very lightly. I've been trim off the excess clay leaving about half inch all the way around. I sandwich the tile between two pieces of sheet rock to dry to leather hard stage. I've been trim the tile to the actual tile pattern and then I traced my design on top. I'll let that dry another three hours. I then carve my design. I do that about 3 times because I'm doing it very lightly to go in little by little. I'm actually just outlining it all so there's some definition between the background and the actual design. I never rest my whole hand on the tile I'm only using my fingertips. I've been put the sheet rock back on top and place it on the drying rack. Then I flip it every 24 hours for three days for drying evenly. And replacing sheet rock as it becomes wet. During the whole process of drying I do keep it covered with sheet of plastic After that I take it off completely and put it on a heavy-duty wire industrial baking rack to dry completely. I llet all tiles dry for three weeks before I clean them up ready to fire for bisque firing. Thank you everyone for your trying to help. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted July 20, 2014 Report Share Posted July 20, 2014 I quite like the cracks, it looks a bit like a person. Link to comment Share on other sites More sharing options...
Guest JBaymore Posted July 20, 2014 Report Share Posted July 20, 2014 Does anyone ELSE have access to your studio where the kiln is? best, .......................john PS: I've only seen cracking like this in 40+ years from one type of thing. Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 20, 2014 Report Share Posted July 20, 2014 What was that one thing? I've never seen this kind of cracking. Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 Does anyone ELSE have access to your studio where the kiln is? best, .......................john PS: I've one seen cracking like this in 40+ years from one type of thing. No.just me and my husband here and he stays clear. What was that one thing? Link to comment Share on other sites More sharing options...
Guest JBaymore Posted July 20, 2014 Report Share Posted July 20, 2014 Looks like the stack of tiles were put down hard. Broken in handling. I was wondering if someone else had picked up that stack and set it down harder than it should have been. Other that that........ I've never seen that kind of cracking. Bizzare. best, .....................john Link to comment Share on other sites More sharing options...
JoLinDesigns Posted July 20, 2014 Author Report Share Posted July 20, 2014 Looks like the stack of tiles were put down hard. Broken in handling. I was wondering if someone else had picked up that stack and set it down harder than it should have been. Other that that........ I've never seen that kind of cracking. Bizzare. best, .....................john Only I handle them and I placed them very gently one x one so I know that wasn't it. I never picked up more than one tile at any time during the whole process. Yes. Bizarre!! Thank you. Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 20, 2014 Report Share Posted July 20, 2014 Could you post more pictures showing how other tiles broke? Link to comment Share on other sites More sharing options...
Benzine Posted July 20, 2014 Report Share Posted July 20, 2014 Like Chris said, to me the cracks don't even look jagged, like most cracks I've seen. John's suggestion makes sense. I have my students make slab relief sculptures. Most of the breaks come from when the students just drop the project on a surface. Those breaks, almost always, follow a weak part of the slab, like where the student carved in. Link to comment Share on other sites More sharing options...
Natania Posted July 21, 2014 Report Share Posted July 21, 2014 My Laguna B-mix 5 plates once cracked kind of like this (only one jagged crack down the middle) when I peaked in the kiln too early and let in a blast of cool air. I heard them go right then and realized that I'd just done a really dumb thing. Did yours cool too quickly, even though the error said "failure to cool"? Link to comment Share on other sites More sharing options...
bciskepottery Posted July 21, 2014 Report Share Posted July 21, 2014 For future firings, you might want to think about clay slats between tiles and between the kiln shelf and the bottom tile of the stack. A quarter inch thick slat, maybe an inch or so wide should do, in various lengths. Slats, or coils, would allow for air circulation during cooling. It would also minimize the chance for the tile to snag on uneven kiln wash or other tiles while the tiles expand/contract during firing. Also think about carving out portions of the reverse side of your tiles; again, that would give you air pockets that will help on cooling, etc. From your picture, it appears the tiles are solid. At least for the tile in the picture, which I am guessing was the top tile on the top shelf, my inclination is to think uneven cooling -- with the outer edges and sides cooling faster than the middle/core (which was also retaining heat from the tile underneath. As for the middle stack, I think too much heat retention from a too dense stack. Just give them some air in between. Link to comment Share on other sites More sharing options...
Chris Campbell Posted July 21, 2014 Report Share Posted July 21, 2014 >The FTC error message is nothing to worry about, as you surmised. FTC means "Failed to Cool." FTC appears during a cooling segment and means the programmed cooling rate is faster than the kiln can cool down. To eliminate the FTC message during your next firing, program a slower cooling rate. Since the kiln cools down more slowly than the programmed rate, you may be able to eliminate that cooling segment altogether.< This explanation is from the Paragon site which leads me to ask the questions ... Did you program in your own schedule for this firing rather than just firing it to Cone 04? The addition of hold time, cooling temps etc. makes me wonder. Did you have any witness cones to tell you what temp the kiln got to? Or did not get to? Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.