Mullins Pottery 18 Report post Posted November 15, 2018 Hi all, I've posted about this local clay body before and I'm checking with the forum to get ideas on trouble shooting another issue. I'm firing to cone 05/04. The body itself is a beautiful lowfire body but after the bisque it gets a white scum on the surface . I'm not sure what it is that's causing the whiting but I think that the clay body would be gallery quality were it not for this blemish. I have sanded the surface after firing and the white can be removed. Obviously this is not a solution but it confirms that there is a beautiful clay body just below the surface. Any ideas of how I can resolve this kind of issue in the clay refining stage? I have links for some images below https://drive.google.com/file/d/0BwDDXHDlS0HGMHVKZVE1VDJuNkUzY2JIbXFFZ2NwMWJ6RHR3/view?usp=sharinghttps://drive.google.com/file/d/0BwDDXHDlS0HGa2Q1LXFkMy1sLVlMaGJBdkE3djN5RUtxNnhJ/view?usp=sharinghttps://drive.google.com/file/d/0BwDDXHDlS0HGMjZQZ1kzb1JnQklZbzc1WExhM1Q2VWVUVjFz/view?usp=sharinghttps://drive.google.com/file/d/0BwDDXHDlS0HGSjFXa2MycWRLcVZwVlJPNWxMM0VYTjlwQ0tn/view?usp=sharing Share this post Link to post Share on other sites
liambesaw 590 Report post Posted November 15, 2018 (edited) Probably soluble salts. I know some clay bodies have barium added to mitigate this. Could also be from a lack of oxygen during the bisque. Sometimes my red clay gets like that if I fire too fast with not enough air. Edited November 15, 2018 by liambesaw Share this post Link to post Share on other sites
neilestrick 2,697 Report post Posted November 15, 2018 Add 0.5% barium carb to your clay to eliminate scumming. Disperse the barium well in water first or you'll get white specks. Share this post Link to post Share on other sites
Mullins Pottery 18 Report post Posted November 15, 2018 (edited) Perfect thanks for the info! secondary question for the 300lb that I've already processed and have been aging for several months lol. Any ideas of what i might be able to do to get rid of that after bisque? or do i just need to bite the bullet and start over? I don't have a pugger all this clay is being dried in an inverted perforated metal table outside with sheets for a liner. Winter is just getting started here in southern Utah. Edited November 15, 2018 by Mullins Pottery needed to add a bit Share this post Link to post Share on other sites
liambesaw 590 Report post Posted November 15, 2018 3 minutes ago, Mullins Pottery said: Perfect thanks for the info! secondary question for the 300lb that I've already processed and have been aging for several months lol. Any ideas of what i might be able to do to get rid of that after bisque? or do i just need to bite the bullet and start over? I don't have a pugger all this clay is being dried in an inverted perforated metal table outside with sheets for a liner. Winter is just getting started here in southern Utah. Does the scum stick around after the glaze firing? I suppose it probably does since your clay is a lowfire one. It doesn't on my cone 6 stuff. Share this post Link to post Share on other sites
Mullins Pottery 18 Report post Posted November 15, 2018 I've fired it to 04 and cone 10 so I haven't fired any other temps to test. At cone 10 the clay turns black and has no sign of scumming. Share this post Link to post Share on other sites
