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thinner

1. n. [Drilling Fluids]
Another term for deflocculant, a thinning agent used to reduce viscosity or prevent flocculation; incorrectly called a "dispersant." Most deflocculants are low-molecular weight anionic polymers that neutralize positive charges on clay edges. Examples include polyphosphates, lignosulfonates, quebracho and various water-soluble synthetic polymers.
Synonyms: deflocculant
Antonyms: flocculant