A method of forming a pot for an array of hollow fibre membranes (7) is provided, including the steps of placing the ends (6) of the fibre membranes (7) in a mould (5); forming a first layer (20) of curable resin material in a non-cured state around the fibre membrane ends (6), applying a second layer (21) of a polyurethane resin material to the first layer (20) prior to full curing of the first layer, the polyurethane resin material layer being chemically reactive with the first layer material to form an adhesive bond therebetween; at least partially curing both layers and removing the pot formed from the mould (5), wherein the second layer material is of higher flexibility than the first layer material when each layer is fully cured. Apparatus for performing the method is also disclosed.