Adele H Posted December 1, 2018 Report Share Posted December 1, 2018 I am very very new to ceramics and this site so not sure what I'm doing on both counts. I have made a few pots with low fire earthen ware clay. It fires at 1050 degrees and they have come out quite good. I have glazed 4 now with Duncan crystal glazes and they have been OK too. I glazed my 5th pot with Duncan Envision glaze, fired at 1020 degrees as per instructions. Fired 1 day left until the next to take out so it was completely cold. When I opened the kiln door there was an area of glaze which had flaked off, shivering I think its called. My first thought was Oh bother my second was what to do about it. If I clean off any loose glaze with say emery paper and re-coat with the same glaze, I gave the original 3 coats so 3 coats again and re fire will it stick?? I expect it should be fired at the same temperature or perhaps not?? I only have a small kiln that only fires to 1100 degrees as a maximum. You may gather that I'm a bit out of my depth, but it's a nice pot and I don't really want to bin it, so could anyone advise please? Thank you Link to comment Share on other sites More sharing options...
liambesaw Posted December 1, 2018 Report Share Posted December 1, 2018 Welcome to the forums here, Adele! Shivering is a scary defect because a pot can continue to shiver and the pieces are very sharp glass. It generally indicates a poor glaze fit for your clay body, and with commercial glazes there's not much you can do to adjust them. Trying to reglaze the areas that shivered with the same shivering glaze will probably end up shivering again. You can make another pot, but I wouldn't use that glaze on that body again, the result will probably be the same. Link to comment Share on other sites More sharing options...
Chilly Posted December 1, 2018 Report Share Posted December 1, 2018 +1 to Liam's comments above. How certain are you of the firing temperatures? Did you use cones? Firing temperature for Duncan Envisions is 1000 - 1020. Did you overfire it? Link to comment Share on other sites More sharing options...
Adele H Posted December 2, 2018 Author Report Share Posted December 2, 2018 The kiln has a temperature gauge I don't quite understand about the cone thing. I set the kiln and it does its stuff! The kiln was new and I've only used it 10 times so hopefully it is accurate. The other items I have fired exactly the same way and they have all been OK. I've rubbed down the flaky bit and am re coating it, what temperature do you think I should fire it at? I've nothing to loose as the pot isn't any good as it is, I'll use it as an experiment!! Thanks for all you help. Link to comment Share on other sites More sharing options...
Babs Posted December 2, 2018 Report Share Posted December 2, 2018 Temp your meant to fire to to ensure your glaze will be mature Link to comment Share on other sites More sharing options...
Adele H Posted December 2, 2018 Author Report Share Posted December 2, 2018 Hi, yes I gather that but I have a temperature gauge on the kiln so have been using that. I only have a small table top kiln which doesn't have any facility to use cones. I think on the bigger kilns you put the cone into a mechanism which when the kiln is at temperature it melts and switches the kiln off. I'm only learning and picking things up as I go. Link to comment Share on other sites More sharing options...
Rae Reich Posted December 2, 2018 Report Share Posted December 2, 2018 You can use free-standing cones in your kiln. A set of three cones, your target temp and the next lowest and the next highest, set into a holder near your pot will tell you how close your firing has gotten to your target temp. Link to comment Share on other sites More sharing options...
Adele H Posted December 2, 2018 Author Report Share Posted December 2, 2018 I will give that a go at least I will know if the temperature gauge is accurate. Thank you Link to comment Share on other sites More sharing options...
JohnnyK Posted December 2, 2018 Report Share Posted December 2, 2018 6 hours ago, Adele H said: Hi, yes I gather that but I have a temperature gauge on the kiln so have been using that. I only have a small table top kiln which doesn't have any facility to use cones. I think on the bigger kilns you put the cone into a mechanism which when the kiln is at temperature it melts and switches the kiln off. I'm only learning and picking things up as I go. The device you're talking about is called a "Kiln-sitter" which you don't have on your kiln. However the cones we are talking about are usually free standing (easiest for you to use) and get placed on the shelf that your pot is on. The glaze temp you are talking about is cone 06, so you would use are cones 07, 06, and 05 to give you an indication of the accuracy of your temp gauge. You can go here to get a little better idea of the cone application. http://www.overglazes.com/PDF/Orton-Cone-Chart-C.pdf Good luck, JohnnyK Link to comment Share on other sites More sharing options...
Chilly Posted December 2, 2018 Report Share Posted December 2, 2018 Without using cones, you won't know if your pots have received enough time at a temperature. Think of baking a fruit cake. You don't put it into a cold oven and switch the oven off as soon as it reaches the required temperature. You keep it at the set temp for an amount of time. It's similar with pottery. Cones measure heat/work. The amount of work that the temperature has applied to the pots. Free-standing cones or cones in a pad of clay will show this. A temperature gauge is only half the solution. Link to comment Share on other sites More sharing options...
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