Abstract: A method of producing a ceramic insulating bushing to be filed with dielectric gas under pressure and which is free from any risk of explosion, comprising the following operations:(1) manufacturing a ceramic bushing (10) having an inside surface which is conical over the entire length (L1) of the bushing;(2) making a conical sleeve (30) of strong insulating material, the sleeve having the same cone angle as the inside surface of the bushing and having a length (L2) which exceeds that of the bushing;(3) inserting the sleeve (30) into the bushing until it makes contact with the entire inside surface (20) of the bushing (10); and(4) cutting off the sleeve at the ends of the busing.