ZDillingham Posted October 12, 2022 Report Share Posted October 12, 2022 I’ve been attempting to fire a straight coil, or rod, and 50% of the time it warps or slumps during the firing process. Does anyone have any recommendations on how to prevent this from happening? Many thanks! Quote Link to comment Share on other sites More sharing options...
Pres Posted October 12, 2022 Report Share Posted October 12, 2022 What is the method you are using to make the rod? What is your method of setting the rod up in the kiln? Your firing process? best, Pres Quote Link to comment Share on other sites More sharing options...
ZDillingham Posted October 12, 2022 Author Report Share Posted October 12, 2022 I use an extruder to make the coils. I then either fire them to cone 6 horizontally, or I mount them vertically to these small planter boxes I make to create miniature topiaries. If I fire them horizontally and unattached I then adhere them using epoxy once everything’s been fired to cone 6. In both situations the rod slightly warps. Quote Link to comment Share on other sites More sharing options...
Pres Posted October 12, 2022 Report Share Posted October 12, 2022 Sounds like you may be having a problem with shrinkage in firing. Do you use any grog on the shelf when firing the horizontal coils? I used to use a salt shaker with larger holes to put down a surface of grog on my shelves when firing extruded tile trim pieces or other extrusions that had to lay flat for firing. As to the vertical coils, you are joining them to the slabs after assembly of the form? What if you mount them on the slabs before assembling the form? best, Pres Magnolia Mud Research 1 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 12, 2022 Report Share Posted October 12, 2022 How big are they? Pres 1 Quote Link to comment Share on other sites More sharing options...
Babs Posted October 13, 2022 Report Share Posted October 13, 2022 How are you handling the coil as it leaves the extruder? Cutting in lengths required as it emerges or handling a long length. Could be your handling at that point of process, and your drying process. Are they small enough to hang within your kiln? Callie Beller Diesel and Pres 2 Quote Link to comment Share on other sites More sharing options...
ZDillingham Posted October 13, 2022 Author Report Share Posted October 13, 2022 23 hours ago, Pres said: Sounds like you may be having a problem with shrinkage in firing. Do you use any grog on the shelf when firing the horizontal coils? I used to use a salt shaker with larger holes to put down a surface of grog on my shelves when firing extruded tile trim pieces or other extrusions that had to lay flat for firing. As to the vertical coils, you are joining them to the slabs after assembly of the form? What if you mount them on the slabs before assembling the form? best, Pres Hi Pres, I’m in a community studio and I don’t believe they use any grog on the kiln shelves. I can ask about it though. With the vertical coils I join them after assembly of the planter by inserting the coil into the planter which is essentially a box. I think I’ve found that firing them horizontally and adhering after all firings is the best bet because if I join them vertically when building and it warps then the whole piece is ruined. Here is a picture of my topiaries: https://ibb.co/xFzbc4P Quote Link to comment Share on other sites More sharing options...
ZDillingham Posted October 13, 2022 Author Report Share Posted October 13, 2022 13 hours ago, Babs said: How are you handling the coil as it leaves the extruder? Cutting in lengths required as it emerges or handling a long length. Could be your handling at that point of process, and your drying process. Are they small enough to hang within your kiln? I’ve been told I should maybe start hand rolling my coils instead of using the extruding because of clay memory. A teacher once told me if I use the extruder I should have a board parallel to the extruded coil and immediately let us rest on the board straight so it’s never bent in any way. To be honest i haven’t been doing this so maybe that’s part of the problem? Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
Pres Posted October 13, 2022 Report Share Posted October 13, 2022 Looking at your pieces, I am assuming that the coils are part of the square decoration in the slab. I wonder if the process might be easier if you carved the inset into the slab instead of adding the coils on. You could always make a wooden tool by drilling a hole in a piece of wood, then cutting the wood so that it cuts through part of the hole allowing you to crape clay away exposing a coil in the slab. Just a thought. best, Pres Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted October 14, 2022 Report Share Posted October 14, 2022 A lot of tension gets set up in the first couple hours of clay drying. It often isn’t evident in bone dry or even bisque fired clay, but really shows up when the clay is fired to maturity. A rod seems like it would dry very evenly, but, like a tile, the part touching the ware board dries slower. I suggest not only hand rolling them a little after extruding, but also turning them slightly as they dry so that happens as evenly as possible. Especially over the first couple hours. Pres 1 Quote Link to comment Share on other sites More sharing options...
Min Posted October 14, 2022 Report Share Posted October 14, 2022 A different approach would be slip cast the rods. It would mean making a mold but that would be fairly straightforward, could use dowels (sealed and soaped) for the rod shapes then cast a mold with them. More work to get set up but once you have a mold made slipcasting them would be quick. Could leave them dry n the molds so there would be nil to minimal warping while drying. Also, do you have to have them fired to cone 6 or would a lowfire casting slip be okay? Callie Beller Diesel, Pres and Kelly in AK 3 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 14, 2022 Report Share Posted October 14, 2022 I agree that plastic memory seems to be playing a part here. Another solution might be to check with your supplier to see if they have a clay that’s meant for tile work. It won’t be as plastic, but it’ll be more resistant to the warping. Even a grogged, high fire sculpture body might work, because it won’t be as vitreous and move as much if you’re only firing to cone 6. Pres and Magnolia Mud Research 2 Quote Link to comment Share on other sites More sharing options...
Chilly Posted October 30, 2022 Report Share Posted October 30, 2022 On 10/12/2022 at 3:09 PM, ZDillingham said: miniature topiaries They are lovely, and in real life would be very unlikely to have perfectly straight trunks. If none of the above suggestions improve your trunks, maybe you could learn to love the twists and curves, or switch to a different medium for the trunks. Quote Link to comment Share on other sites More sharing options...
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