Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They can be divided into closed and open cell structures. In this paper the open cell structures, called sponges, were treated. A new technique to manufacture sponges by plaster investment casting was described. Experimental results show that it is essential to make a sound plaster mould by casting plaster slurry into the polyurethane foams and infiltrate the open channels of the baked plaster mold by molten metal. The optimal processes include plaster slurry preparation, plaster mold baking, and molten metal infiltration. The sponge sample with porosity of 97% is presented. Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They can be divided into closed and open cell structures. A new technique to manufacture sponges by plaster investment casting was described. Experimental results show that it is essential to make a sound plaster mold by casting plaster slurry into the polyurethane foams and infiltrate the open channels of the baked plaster mold by molten metal. The optimal processes include sponge sample with porosity of 97% is presented.