What to do when glazes drain and drip like this

Thursday 6th October 2016

These are the same dipping glaze, it is variegated and drips look ugly on fired ware. The slurry of the one on the left had a insight-live.com/glossary/86">specific gravity of 1.45, it was creamy and appeared to be good. However, when this bisque porcelain mug was pulled out after the dip and rolled it did this (this is ugly in the firing). Why fix the slurry instead of just rubbing this out? Keep reading. To fix this I added water to decrease the specific gravity to 1.43. Then I added Epsom salts to induce thixotropy and gel it back to a creamy consistency. This time it went on evenly. Although the piece dries enough to handle in less than 30 seconds, it does take longer to dry completely because there is more water in the slurry. An addition of CMC gum would also slow down drying but it would be very tricky to get just the right amount (otherwise dripping could be worse than this). Consider a few of the advantages of thixotropic dipping glazes: They don't settle like a rock in the bucket, they don't go on too thick or in multiple thicknesses, they don't drip and they don't dry too fast.

Pages that reference this post in the Digitalfire Reference Library:

CMC Gum, Thixotropy, Specific gravity

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