The influence of interparticle double‐layer and dipole‐dipole forces on the buildup of ultrafine colloidal particles around a magnetized collection center in a static colloid is considered. Expressions are given and developed, respectively, that describe the double layer and dipole‐dipole interparticle effects in a one‐dimensional particle number gradient. These expressions lend themselves to a description of the effects by a double‐layer diffusion and a dipole‐dipole flocculation coefficient. The size of these coefficients and of the normal thermal diffusion coefficient is compared over a wide range of colloidal particle radius, and ranges of radius are identified in which each coefficient can be dominant. Steady‐state solutions of the transport equation including these coefficients are computed and show that this inclusion can be justified, and is indeed necessary, for significant ranges of particle radius.