Bullet hit squib

Typically, a squib used in movies consists of an encapsulated explosive that is flat, disc-shaped, and weighs 0.5-1.0 grain (0.03-0.06 g). To put that into perspective, a party popper is about 0.25 grain (0.015 g), and a small firecracker is about 2.5 grain (0.15 g). This amount of explosive is suitable for creating a wound that simulates an entry or exit point, using approximately 10-30 ml of fake blood, respectively.[12] The amount of fake blood used also depends on how quickly it will soak the fabric and the desired aesthetic of the visual effect.

To create the squib, the fake blood is filled in a small balloon, packet, or condom that is placed atop the squib. A grooved metal or plastic protective plate that is approximately 25 mm in diameter is then added, followed by padding material.[13][11] The entire assembly is secured with duct tape, leaving small front window for the simulant to burst through the path of least resistance.

Various types of simulants are employed, including wet-based like fake blood, non-staining ones like water[14] (for rehearsals), glycerine[15] (for night-time shoots), or dry-based like dust[16][17] and down feathers[18][19] (for achieving the desired gunshot aesthetic on a down jacket). The entire bullet hit squib weighs approximately 30 g and is about 50 mm in diameter and 15 mm thick. The bottom half of the blood packet is aligned to the squib to produce an aerosolised burst, followed by a stream of fake blood, creating the appearance of a realistic wound like the main figure.[20]

An actor wearing a spent set of scrubs for a movie shoot with six exposed bullet holes fake blood.

Dead-character costumes are modified stage clothes worn by actors who play characters that are killed off. Consideration when selecting a costume should not only be given to the requirements of the script, but also the integrability of the squibs, the overall aesthetic (e.g. brightness, contrast with blood) and the budget (e.g. duplicates and reusability). For bare skin gunshot wounds, prosthetics are sometimes used instead. To ensure multiple takes can be filmed, several stunt pieces with squibs and prescored bullet holes are prepared in addition to the hero piece, which is used in prior scenes and closeups without squibs.

To create the bullet holes on the clothing's fabric, the material must first be weakened by cutting,[8] sanding,[11] scoring,[21] grating[22] or plunging a scoring tool,[23] often required by legislation. Afterwards, the fabric is loosely glued or taped back together. Typically, each replicate of the dead-character costumes is used only once per take, although some types of clothing can be reused.

Waterproof jackets, parkas and down jackets are often reusable for more than one take, as fake blood can be wiped off and reset. Using dry or non-staining simulants can also help reuse the outfits for another take.[14] An example can be seen in "Sara" (1997)[24] where the main character puts on a down jacket in the final scene before being shot, consisting of several takes with the down refilled (although two jackets were used). Jackets are also preferred for their ability to conceal the device's bulge compared to t-shirts, provide more padding, can support multiple squibs, and are easier to wear and remove, thus minimising the risk of accidental rupturing of the blood packet. However, the stronger fabric requires more significant weakening beforehand and/or a more powerful squib.

To ensure that the fake blood is propelled out of the bullet hole and not run down on the inside of the costume, the squibs are aligned to the precut bullet holes and securely taped down or sewn to the costume. This also prevents them from moving when worn by the actor. The squibs are then connected to a trigger, a power source, and sometimes a programmable controller for synchronisation with multiple squibs. The electronics can be placed in the clothing or off camera. A test fire and a rehearsal is performed to check the wiring is correct, adjust the timing and the amount of fake blood if necessary.

The actor can change into the prepared outfit immediately prior to the shot, wear it throughout a scene, or even the entire day.[25] However, to avoid accidental triggering, a two-step ignition procedure should be used, with one switch controlled by the actor and another by the crew off-camera,[8] and both switches need to be turned on before ignition is possible. Squibs can be triggered with a wired or wireless remote by a crew member or by the actor. A wired remote can be run to the actor's hand or down the pants, while a wireless solution would enable the actor to move around and would be self-contained.

• Bulge visibility of bullet hit squibs embedded in tight and loose fitting dead character costumes (labelled)
• 
  Bullet hit squibs with 15 g of fake blood each beneath skin-tight wardrobe on a cycling jersey.
• 
  Bullet hit squibs on loose, thin and light-coloured fabric. Each squib contains 15 g of fake blood.
• 
  Bullet hit squibs (labelled) on a padded jacket and dark-coloured fabric. Each squib contains 25 g of fake blood.

An actor shows and checks the bullet hit squib embedded in his jacket.

When the trigger button is pressed on cue, such as a specific line in the script, a countdown or a location, the squib detonates, bursting the blood packet and ripping open the pre-made bullet hole, creating a convincing visual effect. The actor jolts his body to simulate the reaction of being hit by bullets. The bullet hit squib effect is safe and painless when it is built and padded properly with all safety instructions followed.[8] The actor should also avoid looking directly at the squibs and keep their arms away.[25]

After the stunt, the actor remains still while the technician checks for any misfires. In the unlikely situation of a misfire, the power is first disconnected, the circuits are rechecked, and the squib devices are replaced if necessary. A spare stunt costume can help minimise downtime between takes. If the stunt is executed as planned, the wardrobe department photographs the "aftermath" for continuity purposes.[10][26] The spent wardrobe may be removed for a new take, bullet holes enhanced for the following scene, or cleaned up.[10]

In order to conceal the squibs embedded beneath the costumes and scoring marks on the fabric, the footage is usually cut to a few frames prior to the squibs being fired, to avoid revealing the effect. However, it is also possible to digitally remove them in post-production using a reference frame and content-aware fill, to some extent.[27][28] Additionally, post-production sound effects can further enhance the effect.