Abstract: A method and apparatus for sending a coating material (C) under high pressure into an openable mold (2, 3) which is closed and filled with a moldable material. A chamber (6) is used having one end (7) open toward the inside of the mold and an injection duct (14) emerging in the chamber (6). A piston (38) which can move in the chamber (6) from a first position in which the piston blocks the open end (7) of the chamber, is moved as far as a second position beyond the injection duct (14) in relation to the open end (7) of the chamber. The coating material (C) is injected into the chamber (6) via the injection duct (14) under a first pressure (P0); and with the mold remaining completely closed, the piston (38) is moved toward the first position by applying thereto a force (F2) corresponding, inside the chamber (6), to a second pressure (P2) which is greater than the first pressure (P0). Only thereafter is the mold (2, 3) opened.