Abstract Membranes for use in ultrafiltration are manufactured to obtain a defined pore size which will retain particles, colloids, and soluble polymeric materials with molecular weights above a critical value. The presence of pores or defects which are larger than the desired size will have a deleterious effect. The use of a polymeric dye with a defined molecular weight distribution allows a detection of these oversized pores. The method described is simple, rapid, and nondestructive.
