The Halo Assassination Knife is used by Spartans in Halo 4 and Halo 5. I built this piece as an upgrade for our Master Chief costume with the goal of creating a convention-safe prop that could be cast in rigid resin or flexible rubber while keeping the original details intact.
The project began with a real metal knife that matched the in-game model. The surface was prepped by adding clay to areas that lacked detail in the game. This helped simplify the molding process and allowed those details to be added back later if needed. A 2 part mold was then created by splitting the form down the center and casting it in Smooth-On Mold Max 20 silicone.
Once both halves cured, the original knife was removed and replicas could be produced in a range of materials. Initial casts were made using Smooth Cast 300, a fast-setting rigid resin with a 10 minute demold time. This material held its shape well and was comfortable to handle. Future versions were planned in flexible urethane rubbers such as the Task series from Smooth-On for safer convention use.
By 2020, the original mold had begun to lose detail after producing many resin copies, so a second mold was created using clear silicone rubber. Later casts were produced using Smooth Cast 326 urethane resin and pressure cast to eliminate air bubbles in the handle and fine details.
