nwdennis Posted October 26, 2016 Report Share Posted October 26, 2016 I am working on a project to make large ceramic pieces that have a tendency to warp under their own weight and/or drag. I've been thinking of making a setter of sorts that you could sit a large bowl of a sink into. Is it possible to buy large blocks of refractory material that can be shaped to make custom kiln furniture? Are there companies that make custom kiln furniture? What are some go-to methods of reducing drag? I currently only use kiln wash. Is there a way to differentiate between warp from putting too much weight on a thin section vs drag? Thanks, Nate Link to comment Share on other sites More sharing options...
Marcia Selsor Posted October 26, 2016 Report Share Posted October 26, 2016 coils roll or let pieces roll on them. I use extruded coils for large pieces. For bird bath bowls, I use a thrown ring as a support. and that is raised up on coils as well. This allows air/moisture to be released without trapping it. Sometimes you may see large antique platters that have holes in the base . Same idea. Marcia Link to comment Share on other sites More sharing options...
neilestrick Posted October 26, 2016 Report Share Posted October 26, 2016 Put silica sand under large pieces to allow them to move against the shelf. Buying custom refractories will cost a fortune. Better to make your own out of groggy clay, or shave down soft bricks. You could also cast your own with castable refractory, but that stuff's not cheap. Link to comment Share on other sites More sharing options...
glazenerd Posted October 26, 2016 Report Share Posted October 26, 2016 or get it up off the shelf and reduce the drag... and silica dust the slabs. Nerd Link to comment Share on other sites More sharing options...
Marcia Selsor Posted October 27, 2016 Report Share Posted October 27, 2016 sort of like coils.I arrange them in a radiant pattern rather than a linear pattern. Marcia Link to comment Share on other sites More sharing options...
neilestrick Posted October 27, 2016 Report Share Posted October 27, 2016 or get it up off the shelf and reduce the drag... and silica dust the slabs. Nerd Is that a hard hat or an undermount sink? Link to comment Share on other sites More sharing options...
Mark C. Posted October 27, 2016 Report Share Posted October 27, 2016 I use another slab called a waster slab under heavy /large work and under and on that I would use silica sand as Neil suggested above.This way the work shrinks with the shrinking slab and both move on the grains of sand. I also have some round miniature ceramic high fired balls that are about 1/16 of an inch. These work incredibly well.. I had a friend give me a bag of them in the 80's . They are made by Coors Tek in Golden Colorado-(yes a spin off from the beer company). I inquired about getting more and they sent me to an industrial supplier with a huge minimum order so I tabled that idea. My friend got a sample bag in the 80s back in simpler times. Link to comment Share on other sites More sharing options...
glazenerd Posted October 27, 2016 Report Share Posted October 27, 2016 Is that a hard hat or an undermount sink? Actually that is a green ware mold that I spent months making: including sanding to perfection. I cast several pieces from an old drop in sink that I took out of a remodel. The overflow section is actually not attached: even though it appears that way. Lost it in a bisque fire. My plan was to have a permanent bisque mold, more so the over flow drain assembly. Still PO'ed I lost it; had alot of hours into it. The only good news, still have the over-flow assembly. So now my thought is to throw a round 17 or 19" drop in, and cast an overflow to attach later. Nerd Link to comment Share on other sites More sharing options...
Mark C. Posted October 27, 2016 Report Share Posted October 27, 2016 Nerd I have made many sinks spanning my over 40 years in clay . The last few had innovative overflow. Instead of that being attached to the side wall as your pro to type look like. I made the ceramic overflow in top of sink come out into a small clay tube. I threw a ring and had a small tube on that as well, This was siliconed to bottom of sink after firing process . Then attached a flyable pastil tubing to each for water to flow. This solves all overflow cracking issues and is all hidden under counter. This has worked very well in several I had made. I'm out of the sink business now but thought this tip may help you. Link to comment Share on other sites More sharing options...
nwdennis Posted October 27, 2016 Author Report Share Posted October 27, 2016 It was mentioned to try silica sand. Was there a particular mesh size that works best? Does any bag of ground silica work? I have tried about a 50 mesh silica in the past, but I don't think I applied it right. Is there a type of brick that is better to use in the kiln for shaving or firing? Are there types of brick to avoid or will any fire brick do that job? Do you just make these extruded coils yourself? Thanks, these responses have given me a few ideas to try! Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted October 27, 2016 Report Share Posted October 27, 2016 I don't know that it has to be any particular mesh, as long as it's refractory, and will let the piece roll along as it expands and shrinks through quartz inversion. I used fine grog last week on some large popcorn bowls because that's what I had on hand, and it worked just fine. For shaving bricks, soft brick of some kind is what you want. The rating of it doesn't matter much, assuming you're not firing to cone 14 in a wood kiln, or anything extreme like that. And yes, just use coils you make yourself. Sometimes the best fixes are the low tech ones like this. Link to comment Share on other sites More sharing options...
neilestrick Posted October 27, 2016 Report Share Posted October 27, 2016 The mesh of the silica sand doesn't matter, as long as it is sand, not powder. I've always used 70 mesh because that's what I had on hand from using it as a clay additive. I wouldn't go much finer than that. 50 would work. You just need to sprinkle it on the shelf. It acts like little ball bearings. Link to comment Share on other sites More sharing options...
nwdennis Posted October 27, 2016 Author Report Share Posted October 27, 2016 Thank you all very much! Link to comment Share on other sites More sharing options...
perkolator Posted October 28, 2016 Report Share Posted October 28, 2016 For stuff like this, we simply use broken pieces of old kiln shelf. I break or sometimes cut them into little pieces around 1" square. Place them under the perimeter of your work and they'll help facilitate the sliding. For flat work, I don't use the rigid kiln shelf, I use balls of kiln wadding/putty instead, approx 1" diameter, sometimes larger. Kiln wadding is equal parts: silica, kaolin, and grog or sand. Link to comment Share on other sites More sharing options...
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