Abstract: Apparatus and methods are disclosed which reduce stress formation in potting heads for porous hollow filtration membranes. In one example, there is disclosed a potting sleeve for forming a potting head which includes a first fixed portion and a second portion which is movable relative to the first fixed portion to reduce a peripheral extent thereof. In another example, a method of mounting a porous hollow membrane in a membrane filtration apparatus includes positioning a portion of porous hollow membranes within a mold and introducing a curable potting material into the mold so as to immerse the portion of the porous hollow membranes and at least part of one or more deformable members in the potting material. The method further includes at least partially curing the potting material to form a potting head and removing the potting head and the one or more deformable members from the mold.