Abstract: A process for manufacturing a filter medium including a felt of mineral fibers bonded to a veil. The process forms fibers by a device employing internal centrifuging, that includes a fiberizing spinner dish. Then, a precursor of a binder is sprayed onto the fibers. Then, the fibers are collected on a veil. And then, a heat treatment of the assembly including the fibers and the veil is performed with a controlled thickness to convert the binder precursor into a binder. The filter medium thus obtained allows the production of particularly effective pocket filters.