Suzana Lisanti Posted February 23, 2022 Report Share Posted February 23, 2022 Hi, I just bought some used Saint Gobain silicon carbide shelves to be used in the salt/soda chamber of a wood fired Noborigama. The shelves are traditional silicon carbide, but the thinner 5/8" ones (12" x 24" x 5/8"). The shelves are in very good condition. In order to extend the life of the shelves, I'm wondering if I can use them without kiln wash, and flip them as needed according to the curve in the shelf. This is a private kiln, so I can control the glazes used and the wadding, and after every firing there will be shelf scraping. Is there any reason why kiln wash would be necessary? Thanks in advance for your thoughts! Suzana Link to comment Share on other sites More sharing options...
Russ Posted February 23, 2022 Report Share Posted February 23, 2022 The shelves themselves will be "glazed" by the wood ash at higher temps and the salt and soda will also "glaze" your shelves depending on where they are located in the kiln. IMHO a high quality zircon based kiln wash (check on digitalfire.com for formula) would help with removing the wadding after firing and allow you to maintain your shelves. The wash is extremely refractive containing approximately 80% zircopax and 20% calcined kaolin and a bit of cmc gum. Excellent stuff. I will never ever go back to the old stuff. I assume you paid a pretty penny for the shelves and want them to last... Link to comment Share on other sites More sharing options...
Suzana Lisanti Posted February 24, 2022 Author Report Share Posted February 24, 2022 27 minutes ago, Russ said: The shelves themselves will be "glazed" by the wood ash at higher temps and the salt and soda will also "glaze" your shelves depending on where they are located in the kiln. IMHO a high quality zircon based kiln wash (check on digitalfire.com for formula) would help with removing the wadding after firing and allow you to maintain your shelves. The wash is extremely refractive containing approximately 80% zircopax and 20% calcined kaolin and a bit of cmc gum. Excellent stuff. I will never ever go back to the old stuff. I assume you paid a pretty penny for the shelves and want them to last... Thanks for this reply! Do you every flip your shelves or is the kiln wash always on top? Link to comment Share on other sites More sharing options...
Mark C. Posted February 24, 2022 Report Share Posted February 24, 2022 Kiln wash is always on top-never flip after washing as the wash can flake off and ruin the pots under them salt will really attract to silicon shelves (meaning they get gobs of goobie drops on them) soda not as much but still gets on them if its salt fire wash them if its wood ash -well I may not coat these and see how ikt goes flipping them In my salt kiln I use high alumina dry pressed 1 inch thick english shelves as they resist salt well-any silicon shelve salt attracts to and really must be scraped well on every surface. I wash them as well on top side-to reduce scraping always You will find 5/8th shelve will warp at cone 10-11 pretty fast-since its wadding holding the pots up its not as important to keep them flat- as normal shelves ,the 3/4 shelves hold up better warp wise.than 5/8. I have a pile of 5/8 and 3/4 silicon shelves all warped from 40 years ago just in reduction kiln firing Next time you are out west you can pick up my warped silicone shelves for free-I gave up using them 30 years ago and they are dry stored. Link to comment Share on other sites More sharing options...
Russ Posted February 24, 2022 Report Share Posted February 24, 2022 15 hours ago, Suzana Lisanti said: Thanks for this reply! Do you every flip your shelves or is the kiln wash always on top? Yes i do. The zircon based wash acts differently than the flaky alumina kaolin stuff. I have never ever had any of the zircon wash flake off. I do have to say i use pressed alumina shelves instead of carbide but I doubt that would make a difference . I brush on a thin layer before every firing and I even do the edges as the wood kiln environment is extremely harsh to the porous shelves. Again Ive never had an issue with flaking since I started using the zircon. Link to comment Share on other sites More sharing options...
neilestrick Posted February 24, 2022 Report Share Posted February 24, 2022 Silicon carbide shelves tend to foam in wood and salt firings, so they have to be scraped or ground down after every firing. Some shelves foam more than others. In long firings they can even drip onto the work. In grad school always just sifted silica onto the shelves for salt firings, but used kiln wash for wood firings. The silica scrapes right off, but there's a safety issue with using silica. Zircon wash is great, but expensive. If you do need to flip shelves you can grind them clean. Link to comment Share on other sites More sharing options...
Suzana Lisanti Posted February 24, 2022 Author Report Share Posted February 24, 2022 Thank you Neil, this was a very useful reply with lots of info! Suzana Link to comment Share on other sites More sharing options...
Suzana Lisanti Posted February 24, 2022 Author Report Share Posted February 24, 2022 3 hours ago, Russ said: Yes i do. The zircon based wash acts differently than the flaky alumina kaolin stuff. I have never ever had any of the zircon wash flake off. I do have to say i use pressed alumina shelves instead of carbide but I doubt that would make a difference . I brush on a thin layer before every firing and I even do the edges as the wood kiln environment is extremely harsh to the porous shelves. Again Ive never had an issue with flaking since I started using the zircon. Wow! So happy to hear there is a precedent for flipping the zircon washed shelves. My firing will be in April so I have some time to compile all the info from these posts, and I'm grateful to everyone who has replied. Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 25, 2022 Report Share Posted February 25, 2022 On 2/23/2022 at 5:38 PM, Russ said: IMHO a high quality zircon based kiln wash I couldn’t agree more. When we used Lees kilnwash $$$$$$ which is zircon based surprisingly it never came off and allowed flipping at will. On 2/23/2022 at 6:06 PM, Suzana Lisanti said: Do you every flip your shelves or is the kiln wash always on top We would flip the zircon washed at will, alternate as necessary to minimize warping. Definitely stayed on the shelves for us. Link to comment Share on other sites More sharing options...
Mark C. Posted February 25, 2022 Report Share Posted February 25, 2022 Bill whats that formula do you know from digital fire? Is it zircopax or milled zircon? Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 25, 2022 Report Share Posted February 25, 2022 3 hours ago, Mark C. said: whats that formula do you know from digital fire? Is it zircopax or milled zircon? I don’t think anyone knows the Lees formula - very big secret but the digital fire zircon has had praised by others ( https://digitalfire.com/picture/2073). Looked for lees for about two years and gave up. I think locked in a safe somewhere. My experience, It was really good stuff though. Link to comment Share on other sites More sharing options...
Russ Posted February 25, 2022 Report Share Posted February 25, 2022 Plainsman kiln wash from digitalfire https://insight-live.com/insight/share.php?z=DDBJSBWmiM Link to comment Share on other sites More sharing options...
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