In previous publications the performance of a high field-high gradient magnetic filter was calculated using a particle trajectory model to obtain the capture cross section of the fibers. The configuration of the particle buildup was assumed to be constant without considering the forces on the particle after impinging on the fiber. We now calculate the equilibrium configuration of particle buildup on the edge of a flat ribbon considering only the magnetic and viscous forces and including the effect of the fluid boundary layer. The configurations obtained as a function of field and flow are consistent with the few approximate direct observations reported in the literature. The performance of the filter, calculated using the particle trajectory model, now modified by this equilibrium buildup configuration, is compared to previously reported experimental results on separation of CuO from Al2O3slurries. A somewhat better fit is now obtained over the entire range of fluid velocity and fields, but an adjustable parameter affecting the viscous drag on the collected particles is required.