Addition of small amounts of a hydrophilic colloid to a hydrophobic sol to possibly make the latter more sensitive to flocculation by electrolyte.
Source:
PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 610 (https://doi.org/10.1351/pac197231040577)