Controlled Flocculation
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Controlled Flocculation
Controlled Flocculation
Ideally, a slip should be adjusted to a state of “controlled flocculation” where it is fluid, yet the finer particles remain agglomerated somewhat. Quality slips are intentionally less fluid than they could be. In a totally deflocculated slip the particles are so free to move that they can settle out in a very hard layer. During a cast, the smaller ones will be drawn toward the mold surface causing differences in particle size distribution and drying shrinkage across the thickness of the clay wall, resulting in drying cracks. In thin slips poor mold release can also occur because the fine clay is able to penetrate very small recesses in the mold surface and “hold on”, resisting release. If you have these problems, vinegar can be added to a slip to flocculate it a little. It is quite remarkable to see what a capful of vinegar will do for a bucket of settling slip. If a slurry is in just the right state, it should gel slightly while standing over night since this holds all particles in suspension. Re-mixing will loosen it and the skip should flow freely again.
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| Kristle Jones |
