This procedure was developed to provide a method for evaluating fourdrinier drainage. It permits the study of the formation rate and retention distribution over any part or number of parts throughout the length of a fourdrinier. Also, it permits comparisons of forming rates for different fourdrinier equipment, furnishes, chemical additives or refining methods. The method used is a mass balance using consistency and ash determinations along with mass throughput as given by reel production data.