Do grog additions always produce better drying performance?

Friday 24th January 2014

This DFAC test for drying performance compares a typical white stoneware body (left) and the same body with 10% added 50-80 mesh molochite grog. The character of the crack changes somewhat, but otherwise there appears to be no improvement. While the grog addition reduces drying shrinkage by 0.5-0.75% it also cuts dry strength (as a result, the crack is jagged, not a clean line). The grog vents water to the surface better, notice the soluble salts do not concentrate as much. Another issue is the jagged edges of the disk, it is more difficult to cut a clean line in the plastic clay.

Pages that reference this post in the Digitalfire Reference Database:

Molochite, DFAC Drying Factor, The Black Art of Drying Ceramics Without Cracks, Drying Performance, Drying Shrinkage

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of