When pressure casting it is best to leave the part in the tank at a minimum of 60 PSI until it is fully cured. Removing it too soon may distort the part if areas of the resin or rubber haven't cured enough to be stable.
Be sure to produce the mold and the cast parts under the same pressure. If you do not make the mold under pressure, and then try to cast parts in that mold under pressure, the parts may have surface defects (pimples). These are caused by the pressure collapsing internal bubbles that are present in the mold.