ronfire Posted August 26, 2019 Report Share Posted August 26, 2019 I am making some sinks and find they break on the glaze fire and not the bisque. Is this because my glaze fire is a faster firing? bisque to C04 and glaze to C6 with a sitter. The difference is on a bisque I turn up each section 1 hour intervals and on glaze I turn on all 3 zones to low, then med, then high. Link to comment Share on other sites More sharing options...
liambesaw Posted August 26, 2019 Report Share Posted August 26, 2019 Perhaps a low expansion glaze on only one surface. Basically the glaze pulling apart the sink. That's just something that came to mind, but we will see what others think. Link to comment Share on other sites More sharing options...
Babs Posted August 27, 2019 Report Share Posted August 27, 2019 Maybe a photo could help. Sand under sink to ease movement on shelves. Big heavy items I would be easing up to 600 on both firings Link to comment Share on other sites More sharing options...
neilestrick Posted August 27, 2019 Report Share Posted August 27, 2019 Are you glazing both sides of the sink? Photos, please. Link to comment Share on other sites More sharing options...
ronfire Posted August 27, 2019 Author Report Share Posted August 27, 2019 Both sides are glazed and fired on rollers to cone 6. Clay is plainsman stoneware and clear glaze with underglaze. Most sinks are 14" The cracks do not have the sharp edge so it must be cracking on the heat up. This is one that worked. Link to comment Share on other sites More sharing options...
neilestrick Posted August 27, 2019 Report Share Posted August 27, 2019 Where are the cracks? From the lip down, around the base,....? Link to comment Share on other sites More sharing options...
liambesaw Posted August 27, 2019 Report Share Posted August 27, 2019 Cracking on the way up? Are you firing fast through the 1000-1100 mark? Link to comment Share on other sites More sharing options...
ronfire Posted August 27, 2019 Author Report Share Posted August 27, 2019 Cracks are around the base to the outside. I have a sitter so I cant tell the rate of temp increase. I am trying a slow fire like I do the Bisque. 1 Hr on the bottom low then add the middle then add the top each hour. Repeat the same for medium then all to high. Link to comment Share on other sites More sharing options...
neilestrick Posted August 27, 2019 Report Share Posted August 27, 2019 Cracks around the base of a bowl usually indicate that it is too thick in that area. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.