The present application relates to a gel formulation that is stabile for storage, comprising at least two substantially un-mixed hydrogels, wherein each hydrogel contains at least one electrolyte-sensitive thickener. Also, one of the hydrogels (phase A) contains at least one material A that is not compatible with at least one of the materials B contained in another hydrogel (phase B), or that is not compatible therewith in the amounts in which said materials B are contained in the gel formulation.