KLackler Posted January 31, 2023 Report Share Posted January 31, 2023 My kiln shelves are flaking apart and my question is, are they salvageable? And if so, how? They were bought second hand but lightly used, and I only fire them to cone 6, sometimes cone 7 as I have hot spots in my kiln. It just started happening after about 2 years of regular use (2-3x a month). It seems like there would be no way to get them flat again without grinding the whole shelf down, and it is happening on both sides. I'd really prefer not to buy new shelves... Quote Link to comment Share on other sites More sharing options...
neilestrick Posted January 31, 2023 Report Share Posted January 31, 2023 Hi @KLackler, welcome to the forum! Can you post a pic of your shelves? Is it just a layer of wash flaking off, or is the shelf itself delaminating or something weird like that? What type of shelf- silicon carbide, cordierite, etc? Quote Link to comment Share on other sites More sharing options...
KLackler Posted February 1, 2023 Author Report Share Posted February 1, 2023 I had to figure out how to resize the images So this is a photo of one of them. I'm not sure what kind of shelf it is, but it's not very thick, which I love because it's not too heavy. They warp pretty badly, and I just keep flipping them which seems to help. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted February 1, 2023 Report Share Posted February 1, 2023 Thanks for posting a pic. To me that looks like a coating of crappy kiln wash flaking off. Some cheap washes will start to fuse like that and eventually flake off. Unfortunately, you'll have to grind it off, although you may be able to scrape a good amount of it off first. When it's clean and smooth again, re-wash them with a decent high-alumina wash. Kelly in AK, Pres, Rae Reich and 1 other 4 Quote Link to comment Share on other sites More sharing options...
KLackler Posted February 1, 2023 Author Report Share Posted February 1, 2023 Darn! The flakes are pretty thick, and underneath is not smooth- it's pitted and crumbly. In order to make the shelf flat again I think I'd have to grind the whole surface on both sides, and maybe sand it smooth. Does that seem reasonable or maybe it's not salvageable? I will definitely check my kiln wash and get something better-I've just been using whatever my local ceramic stores sell, so I didn't think too much of it. Thank you so much for the help! Quote Link to comment Share on other sites More sharing options...
Mark C. Posted February 1, 2023 Report Share Posted February 1, 2023 Make your own wash-the commercial stuff is crap-that stuff should grind off easy-use a 4 inch hand grinder Kelly in AK, Rae Reich, Magnolia Mud Research and 1 other 4 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted February 1, 2023 Report Share Posted February 1, 2023 I suggest weighing how much labour is involved in fixing these, and decide whether or not you want to spend a whole lot of time, additional materials and then money, or just go straight to spending a little money. You’re right, you will have to grind them down and reapply a better kiln wash. Sanding isn’t necessary if you’re applying kiln wash. If you don’t own a grinder, you have to get that, plus any PPE you don’t own yet. It’s a loud, messy job that takes an afternoon, but isn’t the end of the world. It’s what I’d recommend if you hadn’t mentioned the warping which you were compensating for by flipping. If you use a different kiln wash, washes will all eventually flake off. So you won’t be able to flip them anymore without chips getting into the pieces below. If you’ve got the means, just skip to getting new shelves. If you get the thicker corderite ones, they don’t warp, so kiln washing one side is fine. If you spend a little more for lighter hollow core or carbide, they’re more money but are usually a once in a lifetime purchase. Carbide have the bonus of not really holding onto glaze drips. Rae Reich 1 Quote Link to comment Share on other sites More sharing options...
KLackler Posted February 1, 2023 Author Report Share Posted February 1, 2023 I will start grinding and see how it goes. These are for an old Cress kiln I want to replace soon, so I'd rather not get new shelves yet. Thanks for all the ideas! Rae Reich and Pres 2 Quote Link to comment Share on other sites More sharing options...
Babs Posted February 3, 2023 Report Share Posted February 3, 2023 Not sure where you are but your shelf is disintegrating. Mine did that would " blister" and crack then being brittle sloughs off, flipping them the crumbs flake off onto your glazed pots. Think it's an age thing. Occurred on bottom surface of shelves in my case. Not a flipper. shiny surface, maybe a build up of deposit from many years of glaze firing. Quote Link to comment Share on other sites More sharing options...
KLackler Posted February 3, 2023 Author Report Share Posted February 3, 2023 I've had the shelves outside but covered. It really only started happening maybe 6 firings ago, and I've used these at cone 6/7 for about 2.5 years. I just realized I had changed my kiln wash right about then, I wonder if that's what did it. The wash isn't on super thick. But it definitely looks like the shelf is degrading to me too. I will try grinding, then using a different kiln wash only on one side and see how they do. Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 4, 2023 Report Share Posted February 4, 2023 5 hours ago, KLackler said: I've had the shelves outside but covered. Not sure what your elevation is but Northern California has had temperatures near or below freezing lately. It does look like the shelf is delaminating and might have experienced freeze thaw type damage. Just a possibility. Quote Link to comment Share on other sites More sharing options...
Kelly in AK Posted February 4, 2023 Report Share Posted February 4, 2023 (edited) On a side note, that is exactly what my regular kiln shelves did after several soda firings, on the unwashed side (bottom). Posts too. Big flakes peeling off. I switched to silicon carbide shelves for soda. My understanding is that the surface layer ends up with a different coefficient of expansion than the shelf and eventually spalls. Obviously soda super accelerates the process, but it looks the same. Oh, and do as Mark says, make your own kiln wash. It’s simple and you’ll know what’s in it. Edited February 4, 2023 by Kelly in AK Additional text Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted February 6, 2023 Report Share Posted February 6, 2023 I keep my kiln shelves (electric) outside in a tin garden shed year round for the last 5, and so far they’re fine. I wouldn’t expect a freeze thaw cycle to affect kiln shelves unless they’re getting wet. Quote Link to comment Share on other sites More sharing options...
oldlady Posted February 6, 2023 Report Share Posted February 6, 2023 that photo looks just like the shelves that came with an older kiln given to me for my florida studio. the huge chunks broke off very thick and there was nothing i could do to save the shelves. i took one to a machine shop that could grind them but the owner said there was no way to do it. both sides were the same and he showed me that the huge flakes were half of the shelf itself, not kiln wash. Babs 1 Quote Link to comment Share on other sites More sharing options...
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