A method for partial removal of impurities from colloidal silica, the method comprising the steps of: providing a colloidal silica, wherein the microparticle surface area is from 700 m 2 /g to 1100 m 2 /g and the colloid has a percent by weight SiO 2 solids level of at least 15, and separating impurity particles from the colloidal silica, the impurity particles being at least in part charged particles and being selected from the group consisting of salt ions, acids, and bases, wherein the separation is conducted to a degree such that cross-linkage inducing interactions between impurity particles and silanol groups on dispersed-phase particles decreases but not to such a degree that cross-linkage inducing interactions between silanol groups increases, the separation increasing the particle size of the dispersed-phase particles of the colloid by at least 5% without impairing the S-Value, or stability of the colloid, wherein the separation is accomplished using a dilution filtration process in which the filtration is at least in part ultrafiltration, characterized in that the degree to which the impurity particles have been removed is measured by correlating it to a measurement of the change in conductivity of the colloid, whereby the separation of impurity particles proceed until the colloidal system has a conductivity of between 4000 μS/cm to 7000 μS/cm, and in which the process comprises repeatedly diluting then filtering the colloid, the diluting characterized by decreasing the solids-% by weight by between 30 to 80 % by weight of the solids-% by weight present at the start of the process, the filtering, except for a final filtration step, comprises returning the solids-% by weight to within 10-60 % by weight of the solids-% by weight present at the start of the process. providing a colloidal silica, wherein the microparticle surface area is from 700 m 2 /g to 1100 m 2 /g and the colloid has a percent by weight SiO 2 solids level of at least 15, and separating impurity particles from the colloidal silica, the impurity particles being at least in part charged particles and being selected from the group consisting of salt ions, acids, and bases, wherein the separation is conducted to a degree such that cross-linkage inducing interactions between impurity particles and silanol groups on dispersed-phase particles decreases but not to such a degree that cross-linkage inducing interactions between silanol groups increases, the separation increasing the particle size of the dispersed-phase particles of the colloid by at least 5% without impairing the S-Value, or stability of the colloid, wherein the separation is accomplished using a dilution filtration process in which the filtration is at least in part ultrafiltration, characterized in that the degree to which the impurity particles have been removed is measured by correlating it to a measurement of the change in conductivity of the colloid, whereby the separation of impurity particles proceed until the colloidal system has a conductivity of between 4000 μS/cm to 7000 μS/cm, and in which the process comprises repeatedly diluting then filtering the colloid, the diluting characterized by decreasing the solids-% by weight by between 30 to 80 % by weight of the solids-% by weight present at the start of the process, the filtering, except for a final filtration step, comprises returning the solids-% by weight to within 10-60 % by weight of the solids-% by weight present at the start of the process.