there is provided a ceramic fiber casting core used in making cast metal parts comprised of a ceramic fiber structure . the casting core may further comprise a support tube in structural supporting relation to the ceramic fiber structure . there is also provided a method to manufacture the ceramic fiber casting core that comprises mixing ceramic fibers and a binder in a mix tank . pouring the resultant mixed slurry into a vacuum forming tank . inserting a perforated mandrel into the vacuum forming tank . forming a vacuum inside the mandrel resulting in vacuum depositing of the ceramic fiber on the mandrel . removing the ceramic fiber casting core and mandrel from the vacuum forming tank . removing the mandrel , and then drying and curing the ceramic fiber structure . when necessary , locating a support member in structural supporting relation to the ceramic fiber structure . machining the unfinished casting core to a desired outside dimensions .