Bullet hit squib
A bullet hit squib or a blood squib is a practical, pyrotechnic special effect device used mainly in the film industry, TV shows and stage performances and even in first responder moulage training to simulate the appearance of a person being shot and wounded. This is achieved by blowing open a pre-scored hole on the actor's clothing and bursting a fake blood packet with a small explosion, creating an aesthetic that filmmakers and audiences alike have become accustomed to associating with a gunshot wound. The effect is usually carried out with clothing instead of on bare skin in order to conceal the device. While the portrayal is not necessarily accurate or is exaggerated compared to real-life (in the main figure, bullet holes are blown outwards and blood projects through the fabric), it is nevertheless a useful tool to help create a captivating and dramatic scene. The device comprises a squib (a small, tablet-shaped, firecracker-like explosive) with an integrated igniter, a pack of simulant (often fake blood), a protective shield and padding attached to the actor's costume. It is connected to a battery and a remote, allowing the squib to be triggered by the actor or a crew member. History 

Bullet hit squibs were first used in the film industry as early as 1943 in Bataan and 1955 in Pokolenie, with the latter using fake blood added in a condom and a squib, a technique still widely in use today. The use of squibs in filmmaking has become a widely accepted and well-established technique for creating convincing and realistic depictions of violence. This approach has been used in many classic films such as The Matrix (1999), Goodfellas (1990), and The Terminator (1984). In these films, bullet hit squibs were used to create memorable and impactful moments that helped to further the plot and engage the audience. Preparation of the visual effect 
In film production, various experts collaborate to create realistic blood squib effects. Pyrotechnicians build squibs, while costume designer prepare multiple identical outfits for actors. Consultation with the writer, director, producer, and actor is essential for determining squib positions, numbers, and costume design. At least three, sometimes up to six, costumes are used for different takes and camera angles, dress rehearsals, backups, and tests, depending on the budget. This can be costly for independent or low-budget filmmakers. To avoid the audience from noticing, squibs are integrated discreetly into costumes, designed with a low profile and no significant bulge. Careful fabric perforation reduces visibility of the scoring marks. Bullet hit squib device 
A movie squib is typically a flat, disc-shaped explosive weighing 0.5-1.0 grain (0.03-0.06 g) — by comparison, a party popper is about 0.25 grain (0.015 g), and a small firecracker is about 2.5 grain (0.15 g) — is used to create entry or exit wounds with 10-30 ml of fake blood, respectively. This amount also depends on the absorbency of the fabric and the desired visual aesthetic. The blood is filled in a small balloon, packet, or condom placed on the squib, followed by a grooved protective plate and padding. The assembly is secured with duct tape, leaving a small front window for the simulant to burst through. Various simulants, such as fake blood, water (rehearsals), glycerine (night time), or dry substances like dust and feathers (gunshot aesthetic on a down jacket), are used depending on the desired effect. The bullet hit squib assembly weighs approximately 30 g, measuring 50 mm in diameter and 15 mm thick. Aligning the bottom half of the blood packet with the squib produces an aerosolised burst and a stream of fake blood, creating a realistic wound appearance. Dead character costumes 

Dead-character costumes are stage clothes worn by actors who play characters that are killed off, modified to conceal special effects equipment like squibs and wiring, taking into account script and scene requirements, squib integrability, aesthetics, lighting and budget. They therefore play an important role as a figurative canvas, portraying the violence and death through blood spewing out of frayed bullet holes and staining the clothing. For bare skin gunshot wounds, prosthetics may be used. Several stunt pieces with squibs and prescored bullet holes are prepared for multiple takes and camera angles, in addition to the hero piece used in prior scenes and closeups without squibs. To create bullet holes, the fabric is weakened by cutting, sanding, scoring, grating or plunging a scoring tool, often required by legislation, then loosely glued or taped back together. Squib placement should be consistent across all stunt pieces, and each costume is typically used once per take, though some clothing can be reused. Jackets (e.g. waterproof, parka and down) can be wiped clean and reset for multiple takes, making them a preferred choice in addition to their ability to conceal devices, provide padding, support multiple squibs, and be easily worn and removed, minimising the risk of accidental premature rupturing. However, stronger fabric requires more weakening and/or a more powerful squib. Assembly and costume donning 
To ensure fake blood propels outwards and not inside the costume, squibs are aligned with precut bullet holes and securely attached. They are connected to a trigger, power source, and sometimes a programmable controller for synchronisation. Electronics can be placed in clothing or off-camera. Test fires and rehearsals are performed to check for faults and make adjustments to timing or the amount of fake blood as needed. The actor can wear the prepared outfit immediately prior to the shot, throughout a scene, or even the entire day. To prevent accidental triggering, a two-step ignition procedure with remotes controlled by the actor and crew should be used. Squibs can be triggered wired or wirelessly, with the latter solution allowing for more mobility and self-contained electronics. Firing the bullet hit 

Safety instructions and timing of squib explosions are informed before filming to ensure the actor is comfortable with the stunt. The actor should avoid looking at the squibs and keep arms away. When triggered on cue (e.g. a specific line in the script, countdown or location), the squib detonates, bursting the blood packet and ripping open the pre-made bullet hole as the actor reacts, creating a convincing effect. After the stunt, technicians check for misfires. If this occurs, power is disconnected, circuits are rechecked, and squibs replaced if needed. Spare stunt costumes minimise downtime. If successful, the wardrobe department photographs the "aftermath" for continuity and prepares for the next take, scene, or cleanup. Spent wardrobe may be removed for a new take, bullet holes enhanced for the following scene, or cleaned up. Unused costumes modified with squibs are not returned to the costume shop due to damage from pre-scoring the fabric. Post-production 
To minimise visibility of the squibs and scoring marks on the fabric, footage is typically cut to just before squibs fire. Alternatively, digital removal in post-production using reference frames and content-aware fill is also possible to some extent. Additionally, sound effects further enhance the effect during post-production. Alternative practical bullet hit devices 

Budget-conscious filmmakers can create a similar effect without squibs by using a fishing line attached to a washer glued onto a blood pack, pulled through a precut hole. Alternatively, rocket igniters or electric matches can be employed. However, these methods lack the initial puff from squibs and typically produce only a stream of blood. More advanced methods using pneumatics (compressed air) emerged in the 2010s, offering safer options without needing pyrotechnicians, reducing costs. However, they are bulkier, heavier, harder to control, and less reliable and not preferred for multiple bullet hits. Despite not using explosives, they may still be erroneously referred to as "squibs." Initially developed from garden sprayers in the early 2000s, these devices have been refined, but the resulting effect is less convincing with a jet of blood spray instead of an aerosol burst, and rigid tubing is difficult to conceal. Further examples in tv/films

Miscellaneous 
The record for the most squibs ever set off on a person is held by Mike Daugherty in 2005, on whom 157 out of 160 squibs successfully detonated. See also
 Bodily mutilation in film
 Dead-character costume
 Fake blood
 Firecracker
 Practical effect
 Pyrotechnics
 Special effect
 Squib (explosive)

References

Pyrotechnics
Special effects
Stagecraft