A metal flask is then put over the rubber base. Investment (plaster) is mixed and poured into the flask. This material is semi-liquid when first mixed and it engulfs the wax model and sprues. It is then left to harden. The rubber base is removed and the flask is placed in an oven. This burn out process takes about eight hours to complete and reaches a temperature of 1350 degrees. At the end the flask is taken out of the oven and molten gold or platinum is poured into the investment where the wax once was.