A method of agglomerating nanoparticles to form larger agglomerates is shown. The nanoparticles are mixed with a resin to form a first mixture (803) of agglomerates, having sizes over a range that includes agglomerates considered to be too large, suspended in the resin. A bead milling cylinder (802) produces a second mixture (808) with fewer large agglomerates. A filter (1001) removes the remaining large agglomerates. The resulting mill base is cut with a solvent before deployment.