larathompson288 Posted March 4, 2021 Report Share Posted March 4, 2021 Hi there. I recently glazed some items on white stoneware clay. The clay (White Stoneware PF560) was glazed fired after being bisqued at : room --> 600 degrees C at 100 deg/c per hour 600 -> 1230 at 150 deg/c per hour 20 min soak It came out really patchy and there are some air bubbles. If anyone could recommend good firing ramp for this glaze in degrees celcis with timing that would be great - thanks so much Terracolor orange Ember - https://www.scarva.com/en/gb/Terracolor-FS6031-Orange-Ember/m-1772.aspx was the glaze that didnt look very good! Clay was : https://www.bathpotters.co.uk/white-stoneware-pf560 Link to comment Share on other sites More sharing options...
Min Posted March 4, 2021 Report Share Posted March 4, 2021 Patchy areas where you can see the bare clay is called glazed crawling. Crawling comes from either having the glaze on too thickly or bisque that has something on it to prevent the glaze from adhering to the clay. This could be hand lotion or dusty/dirty bisque. The blisters in the first photo could be caused by a number of things, underfiring or overfiring the glaze being the easiest to fix as this is a commercial glaze and we don't have access to the recipe. Are you verifying the firing with cones to see what it actually got to? I'ld slow down the last 100C of firing to 40C and use cones. Here is a link to preprogrammed firing rates used by a US company, it's in F so you'll need to convert to C. Link to comment Share on other sites More sharing options...
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