the graphite gasket are consist of alone expanded graphite or expanded graphite with metal reinforcement. the expanded graphite is produced by high temperature, high pressure and sulphuric acid from nature graphite. the usually density of expanded graphite is for sealing industry is around 1.3 g /cm3. the expanded graphite is possible to use from -240T up to 550″C and pressure according to reinforced and others influence according to producer of sheets. the same like in all others industries can not be absolute purity of material, so also in sealing industry is existing only technical purity of graphite. that’s why the most common amount of graphite is 99″,71 and this purity called industrially purity. for example for the nuclear power plant is used graphite with purity 99,7% and this purity called atomic purity. the sealing effect is depending on the purity of graphite. the rest are active and passive ashes.