Sofia Jacky Posted August 16, 2015 Report Share Posted August 16, 2015 Hello everyone, I wanted to ask why the glaze might break after cooking the piece when it`s cooling off. Thank you very much. SofÃa Jacky Link to comment Share on other sites More sharing options...
Benzine Posted August 16, 2015 Report Share Posted August 16, 2015 You mean after firing it, in the kiln? Is it popping off, on its own, or kind of flaking off? There are a couple reasons glazes can do this. One, is there was something on the ware, before you glazed it ( dust, oils from fingers/ hands, etc) and the glaze doesn't adhere to the clay body. It looks like it does, but because of the dirt or what have you, the glaze doesn't seep into the clay body. The other reason is a glaze fit issue. If the clay body and glaze don't expand/ contract at the same rate, you have problems. If the glaze shrinks more than the clay, you get crazing, which is tiny cracks in the glaze, or daunting, which can cause the ware to crack. If the clay body shrinks more than the glaze, the glaze essentially bunches up upon itself, and then pops off. The latter may be what happened with your work. What cone is your clay body, and what cone is your glaze(s)? Link to comment Share on other sites More sharing options...
Bob Coyle Posted August 17, 2015 Report Share Posted August 17, 2015 benzine nailed it... If you are a newbe, then you should talk to your supplier and get exactly the glaze that will work with your clay. If you are trying to make ovenware or something to cook in, then this is even more important. Making cookware is hard. Give us some more information on what you are trying to do. Link to comment Share on other sites More sharing options...
Sofia Jacky Posted August 19, 2015 Author Report Share Posted August 19, 2015 Thank you for your answers!Actually Bob, I`m newbie and I don`t have a kiln so I send the pieces to someone else kiln. I want to make pieces to cook in so it`s very important the finish. As Benzine describes I realize I have two problems, not one, but two...... One of them is that in some cases the glaze gets crazing, then as the piece is used the cracks stained. The other problem and the biggest one is that once the pieces have been fired and cooled the glaze pops off. Fortunately, it doesn`t happen all the time, but when it does it´s a disaster... I send you some pics of my pieces so you could understand better because my English is not very good... Link to comment Share on other sites More sharing options...
Sofia Jacky Posted August 19, 2015 Author Report Share Posted August 19, 2015 Ok.. I thought I could send photos.... sorry... Link to comment Share on other sites More sharing options...
Bob Coyle Posted August 19, 2015 Report Share Posted August 19, 2015 You can send photos, but you have to go down below where the POST is and select More Reply Options. You english is fine. You get your ideas across very well. Link to comment Share on other sites More sharing options...
Babs Posted August 20, 2015 Report Share Posted August 20, 2015 Were your pots bisque before glazing and firing? Link to comment Share on other sites More sharing options...
sandy miller Posted August 20, 2015 Report Share Posted August 20, 2015 Also cristobalite is a factor. Baking ware can have huge issues with Quartz inversion. Link to comment Share on other sites More sharing options...
Sofia Jacky Posted August 20, 2015 Author Report Share Posted August 20, 2015 Thank you Bob! Here I send the photos! Babs, yes my pots were bisque before glazing and firing. Link to comment Share on other sites More sharing options...
neilestrick Posted August 20, 2015 Report Share Posted August 20, 2015 Shivering. How hot are you firing? Link to comment Share on other sites More sharing options...
Sofia Jacky Posted August 21, 2015 Author Report Share Posted August 21, 2015 Neil, I`m firing the bisque at 950º C (cone 08) and the glaze at 1040ºC (cone 05) Link to comment Share on other sites More sharing options...
PRankin Posted August 21, 2015 Report Share Posted August 21, 2015 Is it a Cone 08 clay or are you firing another kind of clay to Cone 08? That could be the problem. Paul Link to comment Share on other sites More sharing options...
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