A sachet defining a volume. The sachet has a sheet of material fastened to itself and/or another sheet of material and contains a sufficient quantity of absorbent material such that when the sachet is exposed to liquid a swelled volume of the absorbent material exceeds the volume of the sachet, and wherein the fastening means weakens on exposure to liquid. The sheet material may be paper. The absorbent material may be a super absorbent polymer. The super absorbent material may be sodium polyacrylate.
